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{{task|Classic CS problems and programs}}{{Wikipedia}} :In algebra, [[wp:Polynomial long division|polynomial long division]] is an algorithm for dividing a polynomial by another polynomial of the same or lower degree.

Let us suppose a polynomial is represented by a vector, $x$ (i.e., an ordered collection of [[wp:Coefficient|coefficients]]) so that the $i$th element keeps the coefficient of $x^i$, and the multiplication by a monomial is a ''shift'' of the vector's elements "towards right" (injecting ones from left) followed by a multiplication of each element by the coefficient of the monomial.

Then a pseudocode for the polynomial long division using the conventions described above could be:

degree('''P'''): '''return''' the index of the last non-zero element of '''P'''; if all elements are 0, return -∞

polynomial_long_division('''N''', '''D''') ''returns'' ('''q''', '''r'''): // '''N''', '''D''', '''q''', '''r''' are vectors '''if''' degree('''D''') < 0 '''then''' ''error'' '''q''' ← '''0''' '''while''' degree('''N''') ≥ degree('''D''') '''d''' ← '''D''' ''shifted right'' ''by'' (degree('''N''') - degree('''D''')) '''q'''(degree('''N''') - degree('''D''')) ← '''N'''(degree('''N''')) / '''d'''(degree('''d''')) // by construction, degree('''d''') = degree('''N''') of course '''d''' ← '''d''' * '''q'''(degree('''N''') - degree('''D''')) '''N''' ← '''N''' - '''d''' '''endwhile''' '''r''' ← '''N''' '''return''' ('''q''', '''r''')

'''Note''': vector * scalar multiplies each element of the vector by the scalar; vectorA - vectorB subtracts each element of the vectorB from the element of the vectorA with "the same index". The vectors in the pseudocode are zero-based.

• Error handling (for allocations or for wrong inputs) is not mandatory.
• Conventions can be different; in particular, note that if the first coefficient in the vector is the highest power of x for the polynomial represented by the vector, then the algorithm becomes simpler.

'''Example for clarification'''

This example is from Wikipedia, but changed to show how the given pseudocode works.

   0    1    2    3
----------------------


N: -42 0 -12 1 degree = 3 D: -3 1 0 0 degree = 1

<span class="co1">d(N) - d(D) = 2, so let's shift D towards right by 2:</span>


N: -42 0 -12 1 d: 0 0 -3 1

<span class="co1">N(3)/d(3) = 1, so d is unchanged. Now remember that "shifting by 2"
is like multiplying by x<sup>2</sup>, and the final multiplication
(here by 1) is the coefficient of this monomial. Let's store this
into q:</span>
0     1     2
---------------
q:   0     0     1

<span class="co1">now compute N - d, and let it be the "new" N, and let's loop</span>


N: -42 0 -9 0 degree = 2 D: -3 1 0 0 degree = 1

<span class="co1">d(N) - d(D) = 1, right shift D by 1 and let it be d</span>


N: -42 0 -9 0 d: 0 -3 1 0 * -9/1 = -9

                       q:   0    -9     1


d: 0 27 -9 0

N ← N - d


N: -42 -27 0 0 degree = 1 D: -3 1 0 0 degree = 1

<span class="co1">looping again... d(N)-d(D)=0, so no shift is needed; we
multiply D by -27 (= -27/1) storing the result in d, then</span>

q:  -27   -9     1

<span class="co1">and</span>


N: -42 -27 0 0 - d: 81 -27 0 0 = N: -123 0 0 0 (last N)

 <span class="co1">d(N) &lt; d(D), so now r ← N, and the result is:</span>

0   1  2
-------------


q: -27 -9 1 → x2 - 9x - 27 r: -123 0 0 → -123

with Ada.Text_IO; use Ada.Text_IO;

procedure Long_Division is
package Int_IO is new Ada.Text_IO.Integer_IO (Integer);
use Int_IO;

type Degrees is range -1 .. Integer'Last;
subtype Valid_Degrees is Degrees range 0 .. Degrees'Last;
type Polynom is array (Valid_Degrees range <>) of Integer;

function Degree (P : Polynom) return Degrees is
begin
for I in reverse P'Range loop
if P (I) /= 0 then
return I;
end if;
end loop;
return -1;
end Degree;

function Shift_Right (P : Polynom; D : Valid_Degrees) return Polynom is
Result : Polynom (0 .. P'Last + D) := (others => 0);
begin
Result (Result'Last - P'Length + 1 .. Result'Last) := P;
return Result;
end Shift_Right;

function "*" (Left : Polynom; Right : Integer) return Polynom is
Result : Polynom (Left'Range);
begin
for I in Result'Range loop
Result (I) := Left (I) * Right;
end loop;
return Result;
end "*";

function "-" (Left, Right : Polynom) return Polynom is
Result : Polynom (Left'Range);
begin
for I in Result'Range loop
if I in Right'Range then
Result (I) := Left (I) - Right (I);
else
Result (I) := Left (I);
end if;
end loop;
return Result;
end "-";

procedure Poly_Long_Division (Num, Denom : Polynom; Q, R : out Polynom) is
N : Polynom := Num;
D : Polynom := Denom;
begin
if Degree (D) < 0 then
raise Constraint_Error;
end if;
Q := (others => 0);
while Degree (N) >= Degree (D) loop
declare
T : Polynom := Shift_Right (D, Degree (N) - Degree (D));
begin
Q (Degree (N) - Degree (D)) := N (Degree (N)) / T (Degree (T));
T := T * Q (Degree (N) - Degree (D));
N := N - T;
end;
end loop;
R := N;
end Poly_Long_Division;

procedure Output (P : Polynom) is
First : Boolean := True;
begin
for I in reverse P'Range loop
if P (I) /= 0 then
if First then
First := False;
else
Put (" + ");
end if;
if I > 0 then
if P (I) /= 1 then
Put (P (I), 0);
Put ("*");
end if;
Put ("x");
if I > 1 then
Put ("^");
Put (Integer (I), 0);
end if;
elsif P (I) /= 0 then
Put (P (I), 0);
end if;
end if;
end loop;
New_Line;
end Output;

Test_N : constant Polynom := (0 => -42, 1 => 0, 2 => -12, 3 => 1);
Test_D : constant Polynom := (0 => -3, 1 => 1);
Test_Q : Polynom (Test_N'Range);
Test_R : Polynom (Test_N'Range);
begin
Poly_Long_Division (Test_N, Test_D, Test_Q, Test_R);
Put_Line ("Dividing Polynoms:");
Put ("N: "); Output (Test_N);
Put ("D: "); Output (Test_D);
Put_Line ("-------------------------");
Put ("Q: "); Output (Test_Q);
Put ("R: "); Output (Test_R);
end Long_Division;


output:

Dividing Polynoms:
N: x^3 + -12*x^2 + -42
D: x + -3
-------------------------
Q: x^2 + -9*x + -27
R: -123


APL

div←{
{
q r d←⍵
(≢d) > n←≢r : q r
c ← (⊃⌽r) ÷ ⊃⌽d
∇ (c,q) ((¯1↓r) - c × ¯1↓(-n)↑d) d
} ⍬ ⍺ ⍵
}



{{out}}

      N←¯42 0 ¯12 1
D←¯3 1
⍪N div D
¯27 ¯9 1
¯123



BBC BASIC

      DIM N%(3) : N%() = -42, 0, -12, 1
DIM D%(3) : D%() =  -3, 1,   0, 0
DIM q%(3), r%(3)
PROC_poly_long_div(N%(), D%(), q%(), r%())
PRINT "Quotient = "; FNcoeff(q%(2)) "x^2" FNcoeff(q%(1)) "x" FNcoeff(q%(0))
PRINT "Remainder = " ; r%(0)
END

DEF PROC_poly_long_div(N%(), D%(), q%(), r%())
LOCAL d%(), i%, s%
DIM d%(DIM(N%(),1))
s% = FNdegree(N%()) - FNdegree(D%())
IF s% >= 0 THEN
q%() = 0
WHILE s% >= 0
FOR i% = 0 TO DIM(d%(),1) - s%
d%(i%+s%) = D%(i%)
NEXT
q%(s%) = N%(FNdegree(N%())) DIV d%(FNdegree(d%()))
d%() = d%() * q%(s%)
N%() -= d%()
s% = FNdegree(N%()) - FNdegree(D%())
ENDWHILE
r%() = N%()
ELSE
q%() = 0
r%() = N%()
ENDIF
ENDPROC

DEF FNdegree(a%())
LOCAL i%
i% = DIM(a%(),1)
WHILE a%(i%)=0
i% -= 1
IF i%<0 EXIT WHILE
ENDWHILE
= i%

DEF FNcoeff(n%)
IF n%=0 THEN = ""
IF n%<0 THEN = " - " + STR$(-n%) IF n%=1 THEN = " + " = " + " + STR$(n%)


'''Output:'''


Quotient =  + x^2 - 9x - 27
Remainder = -123



C

{{trans|Fortran}}

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <assert.h>
#include <gsl/gsl_vector.h>

#define MAX(A,B) (((A)>(B))?(A):(B))

void reoshift(gsl_vector *v, int h)
{
if ( h > 0 ) {
gsl_vector *temp = gsl_vector_alloc(v->size);
gsl_vector_view p = gsl_vector_subvector(v, 0, v->size - h);
gsl_vector_view p1 = gsl_vector_subvector(temp, h, v->size - h);
gsl_vector_memcpy(&p1.vector, &p.vector);
p = gsl_vector_subvector(temp, 0, h);
gsl_vector_set_zero(&p.vector);
gsl_vector_memcpy(v, temp);
gsl_vector_free(temp);
}
}

gsl_vector *poly_long_div(gsl_vector *n, gsl_vector *d, gsl_vector **r)
{
gsl_vector *nt = NULL, *dt = NULL, *rt = NULL, *d2 = NULL, *q = NULL;
int gn, gt, gd;

if ( (n->size >= d->size) && (d->size > 0) && (n->size > 0) ) {
nt = gsl_vector_alloc(n->size); assert(nt != NULL);
dt = gsl_vector_alloc(n->size); assert(dt != NULL);
rt = gsl_vector_alloc(n->size); assert(rt != NULL);
d2 = gsl_vector_alloc(n->size); assert(d2 != NULL);
gsl_vector_memcpy(nt, n);
gsl_vector_set_zero(dt); gsl_vector_set_zero(rt);
gsl_vector_view p = gsl_vector_subvector(dt, 0, d->size);
gsl_vector_memcpy(&p.vector, d);
gsl_vector_memcpy(d2, dt);
gn = n->size - 1;
gd = d->size - 1;
gt = 0;

while( gsl_vector_get(d, gd) == 0 ) gd--;

while ( gn >= gd ) {
reoshift(dt, gn-gd);
double v = gsl_vector_get(nt, gn)/gsl_vector_get(dt, gn);
gsl_vector_set(rt, gn-gd, v);
gsl_vector_scale(dt, v);
gsl_vector_sub(nt, dt);
gt = MAX(gt, gn-gd);
while( (gn>=0) && (gsl_vector_get(nt, gn) == 0.0) ) gn--;
gsl_vector_memcpy(dt, d2);
}

q = gsl_vector_alloc(gt+1); assert(q != NULL);
p = gsl_vector_subvector(rt, 0, gt+1);
gsl_vector_memcpy(q, &p.vector);
if ( r != NULL ) {
if ( (gn+1) > 0 ) {
*r = gsl_vector_alloc(gn+1); assert( *r != NULL );
p = gsl_vector_subvector(nt, 0, gn+1);
gsl_vector_memcpy(*r, &p.vector);
} else {
*r = gsl_vector_alloc(1); assert( *r != NULL );
gsl_vector_set_zero(*r);
}
}
gsl_vector_free(nt); gsl_vector_free(dt);
gsl_vector_free(rt); gsl_vector_free(d2);
return q;
} else {
q = gsl_vector_alloc(1); assert( q != NULL );
gsl_vector_set_zero(q);
if ( r != NULL ) {
*r = gsl_vector_alloc(n->size); assert( *r != NULL );
gsl_vector_memcpy(*r, n);
}
return q;
}
}

void poly_print(gsl_vector *p)
{
int i;
for(i=p->size-1; i >= 0; i--) {
if ( i > 0 )
printf("%lfx^%d + ",
gsl_vector_get(p, i), i);
else
printf("%lf\n", gsl_vector_get(p, i));
}
}

gsl_vector *create_poly(int d, ...)
{
va_list al;
int i;
gsl_vector *r = NULL;

va_start(al, d);
r = gsl_vector_alloc(d); assert( r != NULL );

for(i=0; i < d; i++)
gsl_vector_set(r, i, va_arg(al, double));

return r;
}

int main()
{
int i;
gsl_vector *q, *r;
gsl_vector *nv, *dv;

//nv = create_poly(4,  -42., 0., -12., 1.);
//dv = create_poly(2,  -3., 1.);
//nv = create_poly(3,  2., 3., 1.);
//dv = create_poly(2,  1., 1.);
nv = create_poly(4, -42., 0., -12., 1.);
dv = create_poly(3, -3., 1., 1.);

q = poly_long_div(nv, dv, &r);

poly_print(q);
poly_print(r);

gsl_vector_free(q);
gsl_vector_free(r);

return 0;
}


Another version

Without outside libs, for clarity. Note that polys are stored and show with zero-degree term first:

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>

typedef struct {
int power;
double * coef;
} poly_t, *poly;

#define E(x, i) (x)->coef[i]

/* passing in negative power to have a zeroed poly */
poly p_new(int power, ...)
{
int i, zeroed = 0;
va_list ap;

if (power < 0) {
power = -power;
zeroed = 1;
}

poly p = malloc(sizeof(poly_t));
p->power = power;
p->coef = malloc(sizeof(double) * ++power);

if (zeroed)
for (i = 0; i < power; i++) p->coef[i] = 0;
else {
va_start(ap, power);
for (i = 0; i < power; i++)
E(p, i) = va_arg(ap, double);
va_end(ap);
}

return p;
}

void p_del(poly p)
{
free(p->coef);
free(p);
}

void p_print(poly p)
{
int i;
for (i = 0; i <= p->power; i++)
printf("%g ", E(p, i));
printf("\n");
}

poly p_copy(poly p)
{
poly q = p_new(-p->power);
memcpy(q->coef, p->coef, sizeof(double) * (1 + p->power));
return q;
}

/* p: poly;  d: divisor;  r: remainder; returns quotient */
poly p_div(poly p, poly d, poly* r)
{
poly q;
int i, j;
int power = p->power - d->power;
double ratio;

if (power < 0) return 0;

q = p_new(-power);
*r= p_copy(p);

for (i = p->power; i >= d->power; i--) {
E(q, i - d->power) = ratio = E(*r, i) / E(d, d->power);
E(*r ,i) = 0;

for (j = 0; j < d->power; j++)
E(*r, i - d->power + j) -= E(d, j) * ratio;
}
while (! E(*r, --(*r)->power));

return q;
}

int main()
{
poly p = p_new(3, 1., 2., 3., 4.);
poly d = p_new(2, 1., 2., 1.);
poly r;
poly q = p_div(p, d, &r);

printf("poly: "); p_print(p);
printf("div:  "); p_print(d);
printf("quot: "); p_print(q);
printf("rem:  "); p_print(r);

p_del(p);
p_del(q);
p_del(r);
p_del(d);

return 0;
}


C++


#include <iostream>
#include <iterator>
#include <vector>

using namespace std;
typedef vector<double> Poly;

// does:  prints all members of vector
// input: c - ASCII char with the name of the vector
//        A - reference to polynomial (vector)
void Print(char name, const Poly &A) {
cout << name << "(" << A.size()-1 << ") = [ ";
copy(A.begin(), A.end(), ostream_iterator<decltype(A[0])>(cout, " "));
cout << "]\n";
}

int main() {
Poly N, D, d, q, r;        // vectors - N / D == q && N % D == r
size_t dN, dD, dd, dq, dr; // degrees of vectors
size_t i;                  // loop counter

// setting the degrees of vectors
cout << "Enter the degree of N: ";
cin >> dN;
cout << "Enter the degree of D: ";
cin >> dD;
dq = dN-dD;
dr = dN-dD;

if( dD < 1 || dN < 1 ) {
cerr << "Error: degree of D and N must be positive.\n";
return 1;
}

// allocation and initialization of vectors
N.resize(dN+1);
cout << "Enter the coefficients of N:"<<endl;
for ( i = 0; i <= dN; i++ ) {
cout << "N[" << i << "]= ";
cin >> N[i];
}

D.resize(dN+1);
cout << "Enter the coefficients of D:"<<endl;
for ( i = 0; i <= dD; i++ ) {
cout << "D[" << i << "]= ";
cin >> D[i];
}

d.resize(dN+1);
q.resize(dq+1);
r.resize(dr+1);

cout << "-- Procedure --" << endl << endl;
if( dN >= dD ) {
while(dN >= dD) {
// d equals D shifted right
d.assign(d.size(), 0);

for( i = 0 ; i <= dD ; i++ )
d[i+dN-dD] = D[i];
dd = dN;

Print( 'd', d );

// calculating one element of q
q[dN-dD] = N[dN]/d[dd];

Print( 'q', q );

// d equals d * q[dN-dD]
for( i = 0 ; i < dq + 1 ; i++ )
d[i] = d[i] * q[dN-dD];

Print( 'd', d );

// N equals N - d
for( i = 0 ; i < dN + 1 ; i++ )
N[i] = N[i] - d[i];
dN--;

Print( 'N', N );
cout << "-----------------------" << endl << endl;

}
}

// r equals N
for( i = 0 ; i <= dN ; i++ )
r[i] = N[i];

cout << "
### ===================
" << endl << endl;
cout << "-- Result --" << endl << endl;

Print( 'q', q );
Print( 'r', r );
}



C#

{{trans|Java}}

using System;

namespace PolynomialLongDivision {
class Solution {
public Solution(double[] q, double[] r) {
Quotient = q;
Remainder = r;
}

public double[] Quotient { get; }
public double[] Remainder { get; }
}

class Program {
static int PolyDegree(double[] p) {
for (int i = p.Length - 1; i >= 0; --i) {
if (p[i] != 0.0) return i;
}
return int.MinValue;
}

static double[] PolyShiftRight(double[] p, int places) {
if (places <= 0) return p;
int pd = PolyDegree(p);
if (pd + places >= p.Length) {
throw new ArgumentOutOfRangeException("The number of places to be shifted is too large");
}
double[] d = new double[p.Length];
p.CopyTo(d, 0);
for (int i = pd; i >= 0; --i) {
d[i + places] = d[i];
d[i] = 0.0;
}
return d;
}

static void PolyMultiply(double[] p, double m) {
for (int i = 0; i < p.Length; ++i) {
p[i] *= m;
}
}

static void PolySubtract(double[] p, double[] s) {
for (int i = 0; i < p.Length; ++i) {
p[i] -= s[i];
}
}

static Solution PolyLongDiv(double[] n, double[] d) {
if (n.Length != d.Length) {
throw new ArgumentException("Numerator and denominator vectors must have the same size");
}
int nd = PolyDegree(n);
int dd = PolyDegree(d);
if (dd < 0) {
throw new ArgumentException("Divisor must have at least one one-zero coefficient");
}
if (nd < dd) {
throw new ArgumentException("The degree of the divisor cannot exceed that of the numerator");
}
double[] n2 = new double[n.Length];
n.CopyTo(n2, 0);
double[] q = new double[n.Length];
while (nd >= dd) {
double[] d2 = PolyShiftRight(d, nd - dd);
q[nd - dd] = n2[nd] / d2[nd];
PolyMultiply(d2, q[nd - dd]);
PolySubtract(n2, d2);
nd = PolyDegree(n2);
}
return new Solution(q, n2);
}

static void PolyShow(double[] p) {
int pd = PolyDegree(p);
for (int i = pd; i >= 0; --i) {
double coeff = p[i];
if (coeff == 0.0) continue;
if (coeff == 1.0) {
if (i < pd) {
Console.Write(" + ");
}
} else if (coeff == -1.0) {
if (i < pd) {
Console.Write(" - ");
} else {
Console.Write("-");
}
} else if (coeff < 0.0) {
if (i < pd) {
Console.Write(" - {0:F1}", -coeff);
} else {
Console.Write("{0:F1}", coeff);
}
} else {
if (i < pd) {
Console.Write(" + {0:F1}", coeff);
} else {
Console.Write("{0:F1}", coeff);
}
}
if (i > 1) Console.Write("x^{0}", i);
else if (i == 1) Console.Write("x");
}
Console.WriteLine();
}

static void Main(string[] args) {
double[] n = { -42.0, 0.0, -12.0, 1.0 };
double[] d = { -3.0, 1.0, 0.0, 0.0 };
Console.Write("Numerator   : ");
PolyShow(n);
Console.Write("Denominator : ");
PolyShow(d);
Console.WriteLine("-------------------------------------");
Solution sol = PolyLongDiv(n, d);
Console.Write("Quotient    : ");
PolyShow(sol.Quotient);
Console.Write("Remainder   : ");
PolyShow(sol.Remainder);
}
}
}


{{out}}

Numerator   : x^3 - 12.0x^2 - 42.0
Denominator : x - 3.0
-------------------------------------
Quotient    : x^2 - 9.0x - 27.0
Remainder   : -123.0


Clojure

This example performs ''multivariate'' polynomial division using [https://en.wikipedia.org/wiki/Buchberger%27s_algorithm Buchberger's algorithm] to decompose a polynomial into its [https://en.wikipedia.org/wiki/Gr%C3%B6bner_basis Gröbner bases]. Polynomials are represented as hash-maps of monomials with tuples of exponents as keys and their corresponding coefficients as values: e.g. 2xy + 3x + 5y + 7 is represented as {[1 1] 2, [1 0] 3, [0 1] 5, [0 0] 7}.

Since this algorithm is much more efficient when the input is in [https://en.wikipedia.org/wiki/Monomial_order#Graded_reverse_lexicographic_order graded reverse lexicographic (grevlex) order] a comparator is included to be used with Clojure's sorted-map—(into (sorted-map-by grevlex) ...)—as well as necessary functions to compute polynomial multiplication, monomial complements, and S-polynomials.

(defn grevlex [term1 term2]
(if (not= 0 comp)
comp
(loop [term1 term1
term2 term2]
(if (empty? term1)
0
comp (- grade1 grade2)] ;; differs from grlex because terms are flipped from above
(if (not= 0 comp)
comp
(recur (pop term1)
(pop term2)))))))))

(defn mul
;; transducer
([poly1]  ;; completion
(fn
([] poly1)
([poly2] (mul poly1 poly2))
([poly2 & more] (mul poly1 poly2 more))))
([poly1 poly2]
(let [product (atom (transient (sorted-map-by grevlex)))]
(doall  ;; for is lazy so must to be forced for side-effects
(for [term1 poly1
term2 poly2
:let [vars (mapv +' (key term1) (key term2))
coeff (* (val term1) (val term2))]]
(if (contains? @product vars)
(swap! product assoc! vars (+ (get @product vars) coeff))
(swap! product assoc! vars coeff))))
(->> product
(deref)
(persistent!)
(denull))))
([poly1 poly2 & more]
(reduce mul (mul poly1 poly2) more)))

(defn compl [term1 term2]
(map (fn [x y]
(cond
(and (zero? x) (not= 0 y)) nil
(< x y) nil
(>= x y) (- x y)))
term1
term2))

(defn s-poly [f g]
(let [f-vars (first f)
g-vars (first g)
lcm (compl f-vars g-vars)]
(if (not-any? nil? lcm)
{(vec lcm)
(/ (second f) (second g))})))

(defn divide [f g]
(loop [f f
g g
result (transient {})
remainder {}]
(if (empty? f)
(list (persistent! result)
(->> remainder
(filter #(not (nil? %)))
(into (sorted-map-by grevlex))))
(let [term1 (first f)
term2 (first g)
s-term (s-poly term1 term2)]
(if (nil? s-term)
(recur (dissoc f (first term1))
(dissoc g (first term2))
result
(conj remainder term1))
(recur (sub f (mul g s-term))
g
(conj! result s-term)
remainder))))))

(deftest divide-tests
(is (= (divide {[1 1] 2, [1 0] 3, [0 1] 5, [0 0] 7}
{[1 1] 2, [1 0] 3, [0 1] 5, [0 0] 7})
'({[0 0] 1} {})))
(is (= (divide {[1 1] 2, [1 0] 3, [0 1] 5, [0 0] 7}
{[0 0] 1})
'({[1 1] 2, [1 0] 3, [0 1] 5, [0 0] 7} {})))
(is (= (divide {[1 1] 2, [1 0] 10, [0 1] 3, [0 0] 15}
{[0 1] 1, [0 0] 5})
'({[1 0] 2, [0 0] 3} {})))
(is (= (divide {[1 1] 2, [1 0] 10, [0 1] 3, [0 0] 15}
{[1 0] 2, [0 0] 3})
'({[0 1] 1, [0 0] 5} {}))))


Common Lisp

Polynomials are represented as lists of degree/coefficient pairs ordered by degree (highest degree first), and pairs with zero coefficients can be omitted. Multiply and divide perform long multiplication and long division, respectively. multiply returns one value, the product, and divide returns two, the quotient and the remainder.

(defun add (p1 p2)
(do ((sum '())) ((and (endp p1) (endp p2)) (nreverse sum))
(let ((pd1 (if (endp p1) -1 (caar p1)))
(pd2 (if (endp p2) -1 (caar p2))))
(multiple-value-bind (c1 c2)
(cond
((> pd1 pd2) (values (cdr (pop p1)) 0))
((< pd1 pd2) (values 0 (cdr (pop p2))))
(t  (values (cdr (pop p1)) (cdr (pop p2)))))
(let ((csum (+ c1 c2)))
(unless (zerop csum)
(setf sum (acons (max pd1 pd2) csum sum))))))))

(defun multiply (p1 p2)
(flet ((*p2 (p)
(destructuring-bind (d . c) p
(loop for (pd . pc) in p2
collecting (cons (+ d pd) (* c pc))))))
(reduce 'add (mapcar #'*p2 p1) :initial-value '())))

(defun subtract (p1 p2)
(add p1 (multiply '((0 . -1)) p2)))

(defun divide (dividend divisor &aux (sum '()))
(assert (not (endp divisor)) (divisor)
'division-by-zero
:operation 'divide
:operands (list dividend divisor))
(flet ((floor1 (dividend divisor)
(if (endp dividend) (values '() ())
(destructuring-bind (d1 . c1) (first dividend)
(destructuring-bind (d2 . c2) (first divisor)
(if (> d2 d1) (values '() dividend)
(let* ((quot (list (cons (- d1 d2) (/ c1 c2))))
(rem (subtract dividend (multiply divisor quot))))
(values quot rem))))))))
(loop (multiple-value-bind (quotient remainder)
(floor1 dividend divisor)
(if (endp quotient) (return (values sum remainder))
(setf dividend remainder


The [[wp:Polynomial_long_division#Example|wikipedia example]]:

 (divide '((3 . 1) (2 . -12) (0 . -42)) ; x^3 - 12x^2 - 42
'((1 . 1) (0 . -3)))           ; x - 3
((2 . 1) (1 . -9) (0 . -27)) ; x^2 - 9x - 27
((0 . -123))                 ; -123


D

import std.stdio, std.range, std.algorithm, std.typecons, std.conv;

Tuple!(double[], double[]) polyDiv(in double[] inN, in double[] inD)
nothrow pure @safe {
// Code smell: a function that does two things.
static int trimAndDegree(T)(ref T[] poly) nothrow pure @safe @nogc {
poly = poly.retro.find!q{ a != b }(0.0).retro;
return poly.length.signed - 1;
}

auto N = inN.dup;
const(double)[] D = inD;
const dD = trimAndDegree(D);
auto dN = trimAndDegree(N);
double[] q;
if (dD < 0)
throw new Error("ZeroDivisionError");
if (dN >= dD) {
q = [0.0].replicate(dN);
while (dN >= dD) {
auto d = [0.0].replicate(dN - dD) ~ D;
immutable mult = q[dN - dD] = N[$- 1] / d[$ - 1];
d[] *= mult;
N[] -= d[];
dN = trimAndDegree(N);
}
} else
q = [0.0];
return tuple(q, N);
}

int trimAndDegree1(T)(ref T[] poly) nothrow pure @safe @nogc {
poly.length -= poly.retro.countUntil!q{ a != 0 };
return poly.length.signed - 1;
}

void main() {
immutable N = [-42.0, 0.0, -12.0, 1.0];
immutable D = [-3.0, 1.0, 0.0, 0.0];
writefln("%s / %s = %s  remainder %s", N, D, polyDiv(N, D)[]);
}


{{out}}

[-42, 0, -12, 1] / [-3, 1, 0, 0] = [-27, -9, 1]  remainder [-123]


E

{{lines too long|E}} This program has some unnecessary features contributing to its length:

• It creates polynomial objects rather than performing its operations directly on arrays.
• It includes code for printing polynomials nicely.
• It prints the intermediate steps of the division.
pragma.syntax("0.9")
pragma.enable("accumulator")

def superscript(x, out) {
if (x >= 10) { superscript(x // 10) }
out.print("⁰¹²³⁴⁵⁶⁷⁸⁹"[x %% 10])
}

def makePolynomial(initCoeffs :List) {
def degree := {
var i := initCoeffs.size() - 1
while (i >= 0 && initCoeffs[i] &lt;=> 0) { i -= 1 }
if (i &lt; 0) { -Infinity } else { i }
}
def coeffs := initCoeffs(0, if (degree == -Infinity) { [] } else { degree + 1 })

def polynomial {
/** Print the polynomial (not necessary for the task) */
to __printOn(out) {
out.print("(λx.")
var first := true
for i in (0..!(coeffs.size())).descending() {
def coeff := coeffs[i]
if (coeff &lt;=> 0) { continue }
out.print(" ")
if (coeff &lt;=> 1 && !(i &lt;=> 0)) {
# no coefficient written if it's 1 and not the constant term
} else if (first) {      out.print(coeff)
} else if (coeff > 0) {  out.print("+ ", coeff)
} else {                 out.print("- ", -coeff)
}
if (i &lt;=> 0) {         # no x if it's the constant term
} else if (i &lt;=> 1) {  out.print("x")
} else {               out.print("x"); superscript(i, out)
}
first := false
}
out.print(")")
}

/** Evaluate the polynomial (not necessary for the task) */
to run(x) {
return accum 0 for i => c in coeffs { _ + c * x**i }
}

to degree() { return degree }
to coeffs() { return coeffs }
to highestCoeff() { return coeffs[degree] }

/** Could support another polynomial, but not part of this task.
Computes this * x**power. */
to timesXToThe(power) {
return makePolynomial([0] * power + coeffs)
}

/** Multiply (by a scalar only). */
to multiply(scalar) {
return makePolynomial(accum [] for x in coeffs { _.with(x * scalar) })
}

/** Subtract (by another polynomial only). */
to subtract(other) {
def oc := other.coeffs() :List
return makePolynomial(accum [] for i in 0..(coeffs.size().max(oc.size())) { _.with(coeffs.fetch(i, fn{0}) - oc.fetch(i, fn{0})) })
}

/** Polynomial long division. */
to quotRem(denominator, trace) {
var numerator := polynomial
require(denominator.degree() >= 0)
if (numerator.degree() &lt; denominator.degree()) {
return [makePolynomial([]), denominator]
} else {
var quotientCoeffs := [0] * (numerator.degree() - denominator.degree())
while (numerator.degree() >= denominator.degree()) {
trace.print("  ", numerator, "\n")

def qCoeff := numerator.highestCoeff() / denominator.highestCoeff()
def qPower := numerator.degree() - denominator.degree()
quotientCoeffs with= (qPower, qCoeff)

def d := denominator.timesXToThe(qPower) * qCoeff
trace.print("- ", d,  "          (= ", denominator, " * ", qCoeff, "x"); superscript(qPower, trace); trace.print(")\n")
numerator -= d

trace.print("  -------------------------- (Quotient so far: ",  makePolynomial(quotientCoeffs), ")\n")
}
return [makePolynomial(quotientCoeffs), numerator]
}
}
}
return polynomial
}

def n := makePolynomial([-42, 0, -12, 1])
def d := makePolynomial([-3, 1])
println("Numerator: ", n)
println("Denominator: ", d)
def [q, r] := n.quotRem(d, stdout)
println("Quotient: ", q)
println("Remainder: ", r)


Output:

Numerator: (λx. x³ - 12x² - 42) Denominator: (λx. x - 3) (λx. x³ - 12x² - 42)

• (λx. x³ - 3.0x²) (= (λx. x - 3) * 1.0x²) -------------------------- (Quotient so far: (λx. x²)) (λx. -9.0x² - 42.0)
• (λx. -9.0x² + 27.0x) (= (λx. x - 3) * -9.0x¹) -------------------------- (Quotient so far: (λx. x² - 9.0x)) (λx. -27.0x - 42.0)
• (λx. -27.0x + 81.0) (= (λx. x - 3) * -27.0x⁰) -------------------------- (Quotient so far: (λx. x² - 9.0x - 27.0)) Quotient: (λx. x² - 9.0x - 27.0) Remainder: (λx. -123.0)

Elixir

{{trans|Ruby}}

defmodule Polynomial do
def division(_, []), do: raise ArgumentError, "denominator is zero"
def division(_, [0]), do: raise ArgumentError, "denominator is zero"
def division(f, g) when length(f) < length(g), do: {[0], f}
def division(f, g) do
{q, r} = division(g, [], f)
if q==[], do: q = [0]
if r==[], do: r = [0]
{q, r}
end

defp division(g, q, r) when length(r) < length(g), do: {q, r}
defp division(g, q, r) do
p = hd(r) / hd(g)
r2 = Enum.zip(r, g)
|> Enum.with_index
|> Enum.reduce(r, fn {{pn,pg},i},acc ->
List.replace_at(acc, i, pn - p * pg)
end)
division(g, q++[p], tl(r2))
end
end

[ { [1, -12, 0, -42], [1, -3] },
{ [1, -12, 0, -42], [1, 1, -3] },
{ [1, 3, 2],        [1, 1] },
{ [1, -4, 6, 5, 3], [1, 2, 1] } ]
|> Enum.each(fn {f,g} ->
{q, r} = Polynomial.division(f, g)
IO.puts "#{inspect f} / #{inspect g} => #{inspect q} remainder #{inspect r}"
end)


{{out}}


[1, -12, 0, -42] / [1, -3] => [1.0, -9.0, -27.0] remainder [-123.0]
[1, -12, 0, -42] / [1, 1, -3] => [1.0, -13.0] remainder [16.0, -81.0]
[1, 3, 2] / [1, 1] => [1.0, 2.0] remainder [0.0]
[1, -4, 6, 5, 3] / [1, 2, 1] => [1.0, -6.0, 17.0] remainder [-23.0, -14.0]



Factor

USE: math.polynomials

{ -42 0 -12 1 } { -3 1 } p/mod ptrim [ . ] bi@


{{out}}


V{ -27 -9 1 }
V{ -123 }



Fortran

{{works with|Fortran|95 and later}}

module Polynom
implicit none

contains

subroutine poly_long_div(n, d, q, r)
real, dimension(:), intent(in) :: n, d
real, dimension(:), intent(out), allocatable :: q
real, dimension(:), intent(out), allocatable, optional :: r

real, dimension(:), allocatable :: nt, dt, rt
integer :: gn, gt, gd

if ( (size(n) >= size(d)) .and. (size(d) > 0) .and. (size(n) > 0) ) then
allocate(nt(size(n)), dt(size(n)), rt(size(n)))

nt = n
dt = 0
dt(1:size(d)) = d
rt = 0
gn = size(n)-1
gd = size(d)-1
gt = 0

do while ( d(gd+1) == 0 )
gd = gd - 1
end do

do while( gn >= gd )
dt = eoshift(dt, -(gn-gd))
rt(gn-gd+1) = nt(gn+1) / dt(gn+1)
nt = nt - dt * rt(gn-gd+1)
gt = max(gt, gn-gd)
do
gn = gn - 1
if ( nt(gn+1) /= 0 ) exit
end do
dt = 0
dt(1:size(d)) = d
end do

allocate(q(gt+1))
q = rt(1:gt+1)
if ( present(r) ) then
if ( (gn+1) > 0 ) then
allocate(r(gn+1))
r = nt(1:gn+1)
else
allocate(r(1))
r = 0.0
end if
end if
deallocate(nt, dt, rt)
else
allocate(q(1))
q = 0
if ( present(r) ) then
allocate(r(size(n)))
r = n
end if
end if

end subroutine poly_long_div

subroutine poly_print(p)
real, dimension(:), intent(in) :: p

integer :: i

do i = size(p), 1, -1
if ( i > 1 ) then
write(*, '(F0.2,"x^",I0," + ")', advance="no") p(i), i-1
else
write(*, '(F0.2)') p(i)
end if
end do

end subroutine poly_print

end module Polynom

program PolyDivTest
use Polynom
implicit none

real, dimension(:), allocatable :: q
real, dimension(:), allocatable :: r

!! three tests from Wikipedia, plus an extra
!call poly_long_div( (/ -3., 1. /), (/ -42., 0.0, -12., 1. /), q, r)
call poly_long_div( (/ -42., 0.0, -12., 1. /), (/ -3., 1. /), q, r)
!call poly_long_div( (/ -42., 0.0, -12., 1. /), (/ -3., 1., 1. /), q, r)
!call poly_long_div( (/ 2., 3., 1. /), (/ 1., 1. /), q, r)

call poly_print(q)
call poly_print(r)
deallocate(q, r)

end program PolyDivTest


Go

By the convention and pseudocode given in the task:

package main

import "fmt"

func main() {
n := []float64{-42, 0, -12, 1}
d := []float64{-3, 1}
fmt.Println("N:", n)
fmt.Println("D:", d)
q, r, ok := pld(n, d)
if ok {
fmt.Println("Q:", q)
fmt.Println("R:", r)
} else {
fmt.Println("error")
}
}

func degree(p []float64) int {
for d := len(p) - 1; d >= 0; d-- {
if p[d] != 0 {
return d
}
}
return -1
}

func pld(nn, dd []float64) (q, r []float64, ok bool) {
if degree(dd) < 0 {
return
}
nn = append(r, nn...)
if degree(nn) >= degree(dd) {
q = make([]float64, degree(nn)-degree(dd)+1)
for degree(nn) >= degree(dd) {
d := make([]float64, degree(nn)+1)
copy(d[degree(nn)-degree(dd):], dd)
q[degree(nn)-degree(dd)] = nn[degree(nn)] / d[degree(d)]
for i := range d {
d[i] *= q[degree(nn)-degree(dd)]
nn[i] -= d[i]
}
}
}
return q, nn, true
}


Output:


N: [-42 0 -12 1]
D: [-3 1]
Q: [-27 -9 1]
R: [-123 0 0 0]



GAP

GAP has built-in functions for computations with polynomials.

x := Indeterminate(Rationals, "x");
p := x^11 + 3*x^8 + 7*x^2 + 3;
q := x^7 + 5*x^3 + 1;
QuotientRemainder(p, q);
# [ x^4+3*x-5, -16*x^4+25*x^3+7*x^2-3*x+8 ]


Translated from the OCaml code elsewhere on the page. {{works with|GHC|6.10}}

import Data.List

shift n l = l ++ replicate n 0

pad n l = replicate n 0 ++ l

norm :: Fractional a => [a] -> [a]
norm = dropWhile (== 0)

deg l = length (norm l) - 1

zipWith' op p q = zipWith op (pad (-d) p) (pad d q)
where d = (length p) - (length q)

polydiv f g = aux (norm f) (norm g) []
where aux f s q | ddif < 0 = (q, f)
| otherwise = aux f' s q'
where ddif = (deg f) - (deg s)
ks = map (* k) $shift ddif s q' = zipWith' (+) q$ shift ddif [k]
f' = norm $tail$ zipWith' (-) f ks


And this is the also-translated pretty printing function.

str_poly l = intercalate " + " $terms l where term v 0 = show v term 1 1 = "x" term v 1 = (show v) ++ "x" term 1 p = "x^" ++ (show p) term v p = (show v) ++ "x^" ++ (show p) terms :: Fractional a => [a] -> [String] terms [] = [] terms (0:t) = terms t terms (h:t) = (term h (length t)) : (terms t)  J From http://www.jsoftware.com/jwiki/Phrases/Polynomials divmod=:[: (}: ; {:) ([ (] -/@,:&}. (* {:)) ] , %&{.~)^:(>:@-~&#)&.|.~  Wikipedia example: _42 0 _12 1 divmod _3 1  This produces the result: ┌────────┬────┐ │_27 _9 1│_123│ └────────┴────┘ This means that $-42-12 x^2+x^3$ divided by $-3+x$ produces $-27-9 x+x^2$ with a remainder of $-123$. Java {{trans|Kotlin}} import java.util.Arrays; public class PolynomialLongDivision { private static class Solution { double[] quotient, remainder; Solution(double[] q, double[] r) { this.quotient = q; this.remainder = r; } } private static int polyDegree(double[] p) { for (int i = p.length - 1; i >= 0; --i) { if (p[i] != 0.0) return i; } return Integer.MIN_VALUE; } private static double[] polyShiftRight(double[] p, int places) { if (places <= 0) return p; int pd = polyDegree(p); if (pd + places >= p.length) { throw new IllegalArgumentException("The number of places to be shifted is too large"); } double[] d = Arrays.copyOf(p, p.length); for (int i = pd; i >= 0; --i) { d[i + places] = d[i]; d[i] = 0.0; } return d; } private static void polyMultiply(double[] p, double m) { for (int i = 0; i < p.length; ++i) { p[i] *= m; } } private static void polySubtract(double[] p, double[] s) { for (int i = 0; i < p.length; ++i) { p[i] -= s[i]; } } private static Solution polyLongDiv(double[] n, double[] d) { if (n.length != d.length) { throw new IllegalArgumentException("Numerator and denominator vectors must have the same size"); } int nd = polyDegree(n); int dd = polyDegree(d); if (dd < 0) { throw new IllegalArgumentException("Divisor must have at least one one-zero coefficient"); } if (nd < dd) { throw new IllegalArgumentException("The degree of the divisor cannot exceed that of the numerator"); } double[] n2 = Arrays.copyOf(n, n.length); double[] q = new double[n.length]; while (nd >= dd) { double[] d2 = polyShiftRight(d, nd - dd); q[nd - dd] = n2[nd] / d2[nd]; polyMultiply(d2, q[nd - dd]); polySubtract(n2, d2); nd = polyDegree(n2); } return new Solution(q, n2); } private static void polyShow(double[] p) { int pd = polyDegree(p); for (int i = pd; i >= 0; --i) { double coeff = p[i]; if (coeff == 0.0) continue; if (coeff == 1.0) { if (i < pd) { System.out.print(" + "); } } else if (coeff == -1.0) { if (i < pd) { System.out.print(" - "); } else { System.out.print("-"); } } else if (coeff < 0.0) { if (i < pd) { System.out.printf(" - %.1f", -coeff); } else { System.out.print(coeff); } } else { if (i < pd) { System.out.printf(" + %.1f", coeff); } else { System.out.print(coeff); } } if (i > 1) System.out.printf("x^%d", i); else if (i == 1) System.out.print("x"); } System.out.println(); } public static void main(String[] args) { double[] n = new double[]{-42.0, 0.0, -12.0, 1.0}; double[] d = new double[]{-3.0, 1.0, 0.0, 0.0}; System.out.print("Numerator : "); polyShow(n); System.out.print("Denominator : "); polyShow(d); System.out.println("-------------------------------------"); Solution sol = polyLongDiv(n, d); System.out.print("Quotient : "); polyShow(sol.quotient); System.out.print("Remainder : "); polyShow(sol.remainder); } }  {{out}} Numerator : x^3 - 12.0x^2 - 42.0 Denominator : x - 3.0 ------------------------------------- Quotient : x^2 - 9.0x - 27.0 Remainder : -123.0  Julia This task is straightforward with the help of Julia's [https://github.com/Keno/Polynomials.jl Polynomials] package.  using Polynomials p = Poly([-42,0,-12,1]) q = Poly([-3,1]) d, r = divrem(p,q) println(p, " divided by ", q, " is ", d, " with remainder ", r, ".")  {{out}}  -42 - 12x^2 + x^3 divided by -3 + x is -27.0 - 9.0x + x^2 with remainder -123.0.  Kotlin // version 1.1.51 typealias IAE = IllegalArgumentException data class Solution(val quotient: DoubleArray, val remainder: DoubleArray) fun polyDegree(p: DoubleArray): Int { for (i in p.size - 1 downTo 0) { if (p[i] != 0.0) return i } return Int.MIN_VALUE } fun polyShiftRight(p: DoubleArray, places: Int): DoubleArray { if (places <= 0) return p val pd = polyDegree(p) if (pd + places >= p.size) { throw IAE("The number of places to be shifted is too large") } val d = p.copyOf() for (i in pd downTo 0) { d[i + places] = d[i] d[i] = 0.0 } return d } fun polyMultiply(p: DoubleArray, m: Double) { for (i in 0 until p.size) p[i] *= m } fun polySubtract(p: DoubleArray, s: DoubleArray) { for (i in 0 until p.size) p[i] -= s[i] } fun polyLongDiv(n: DoubleArray, d: DoubleArray): Solution { if (n.size != d.size) { throw IAE("Numerator and denominator vectors must have the same size") } var nd = polyDegree(n) val dd = polyDegree(d) if (dd < 0) { throw IAE("Divisor must have at least one one-zero coefficient") } if (nd < dd) { throw IAE("The degree of the divisor cannot exceed that of the numerator") } val n2 = n.copyOf() val q = DoubleArray(n.size) // all elements zero by default while (nd >= dd) { val d2 = polyShiftRight(d, nd - dd) q[nd - dd] = n2[nd] / d2[nd] polyMultiply(d2, q[nd - dd]) polySubtract(n2, d2) nd = polyDegree(n2) } return Solution(q, n2) } fun polyShow(p: DoubleArray) { val pd = polyDegree(p) for (i in pd downTo 0) { val coeff = p[i] if (coeff == 0.0) continue print (when { coeff == 1.0 -> if (i < pd) " + " else "" coeff == -1.0 -> if (i < pd) " - " else "-" coeff < 0.0 -> if (i < pd) " -${-coeff}" else "$coeff" else -> if (i < pd) " +$coeff" else "$coeff" }) if (i > 1) print("x^$i")
else if (i == 1) print("x")
}
println()
}

fun main(args: Array<String>) {
val n = doubleArrayOf(-42.0, 0.0, -12.0, 1.0)
val d = doubleArrayOf( -3.0, 1.0,   0.0, 0.0)
print("Numerator   : ")
polyShow(n)
print("Denominator : ")
polyShow(d)
println("-------------------------------------")
val (q, r) = polyLongDiv(n, d)
print("Quotient    : ")
polyShow(q)
print("Remainder   : ")
polyShow(r)
}


{{out}}


Numerator   : x^3 - 12.0x^2 - 42.0
Denominator : x - 3.0
-------------------------------------
Quotient    : x^2 - 9.0x - 27.0
Remainder   : -123.0



Maple

As Maple is a symbolic computation system, polynomial arithmetic is, of course, provided by the language runtime. The remainder (rem) and quotient (quo) operations each allow for the other to be computed simultaneously by passing an unassigned name as an optional fourth argument. Since rem and quo deal also with multivariate polynomials, the indeterminate is passed as the third argument.


> p := randpoly( x ); # pick a random polynomial in x
5       4       3       2
p := -56 - 7 x  + 22 x  - 55 x  - 94 x  + 87 x

> rem( p, x^2 + 2, x, 'q' ); # remainder
220 + 169 x

> q; # quotient
3       2
-7 x  + 22 x  - 41 x - 138

> quo( p, x^2 + 2, x, 'r' ); # quotient
3       2
-7 x  + 22 x  - 41 x - 138

> r; # remainder
220 + 169 x
> expand( (x^2+2)*q + r - p ); # check
0



Mathematica

PolynomialQuotientRemainder[x^3-12 x^2-42,x-3,x]


output:

{-27 - 9 x + x^2, -123}


OCaml

First define some utility operations on polynomials as lists (with highest power coefficient first).

let rec shift n l = if n <= 0 then l else shift (pred n) (l @ [0.0])
let rec pad n l = if n <= 0 then l else pad (pred n) (0.0 :: l)
let rec norm = function | 0.0 :: tl -> norm tl | x -> x
let deg l = List.length (norm l) - 1

let zip op p q =
let d = (List.length p) - (List.length q) in


Then the main polynomial division function

let polydiv f g =
let rec aux f s q =
let ddif = (deg f) - (deg s) in
if ddif < 0 then (q, f) else
let k = (List.hd f) /. (List.hd s) in
let ks = List.map (( *.) k) (shift ddif s) in
let q' = zip (+.) q (shift ddif [k])
and f' = norm (List.tl (zip (-.) f ks)) in
aux f' s q' in
aux (norm f) (norm g) []


For output we need a pretty-printing function

let str_poly l =
let term v p = match (v, p) with
| (  _, 0) -> string_of_float v
| (1.0, 1) -> "x"
| (  _, 1) -> (string_of_float v) ^ "*x"
| (1.0, _) -> "x^" ^ (string_of_int p)
| _ -> (string_of_float v) ^ "*x^" ^ (string_of_int p) in
let rec terms = function
| [] -> []
| h :: t ->
if h = 0.0 then (terms t) else (term h (List.length t)) :: (terms t) in
String.concat " + " (terms l)


and then the example

let _ =
let f = [1.0; -4.0; 6.0; 5.0; 3.0] and g = [1.0; 2.0; 1.0] in
let q, r = polydiv f g in
Printf.printf
" (%s) div (%s)\ngives\nquotient:\t(%s)\nremainder:\t(%s)\n"
(str_poly f) (str_poly g) (str_poly q) (str_poly r)


gives the output:


(x^4 + -4.*x^3 + 6.*x^2 + 5.*x + 3.) div (x^2 + 2.*x + 1.)
gives
quotient:	(x^2 + -6.*x + 17.)
remainder:	(-23.*x + -14.)



Octave

Octave has already facilities to divide two polynomials (deconv(n,d)); and the reason to adopt the convention of keeping the highest power coefficient first, is to make the code compatible with builtin functions: we can use polyout to output the result.

function [q, r] = poly_long_div(n, d)
gd = length(d);
pv = zeros(1, length(n));
pv(1:gd) = d;
if ( length(n) >= gd )
q = [];
while ( length(n) >= gd )
q = [q, n(1)/pv(1)];
n = n - pv .* (n(1)/pv(1));
n = shift(n, -1);           %
tn = n(1:length(n)-1);      % eat the higher power term
n = tn;                     %
tp = pv(1:length(pv)-1);
pv = tp;                    % make pv the same length of n
endwhile
r = n;
else
q = [0];
r = n;
endif
endfunction

[q, r] = poly_long_div([1,-12,0,-42], [1,-3]);
polyout(q, 'x');
polyout(r, 'x');
disp("");
[q, r] = poly_long_div([1,-12,0,-42], [1,1,-3]);
polyout(q, 'x');
polyout(r, 'x');
disp("");
[q, r] = poly_long_div([1,3,2], [1,1]);
polyout(q, 'x');
polyout(r, 'x');
disp("");
[q, r] = poly_long_div([1,3], [1,-12,0,-42]);
polyout(q, 'x');
polyout(r, 'x');


PARI/GP

This uses the built-in PARI polynomials.

poldiv(a,b)={
my(rem=a%b);
[(a - rem)/b, rem]
};
poldiv(x^9+1, x^3+x-3)


Alternately, use the built-in function divrem:

divrem(x^9+1, x^3+x-3)~


Perl

This solution keeps the highest power coefficient first, like [[Polynomial long division#OCaml|OCaml solution]] and [[Polynomial long division#Octave|Octave solution]].

{{trans|Octave}}

use strict;
use List::Util qw(min);

sub poly_long_div
{
my ($rn,$rd) = @_;

my @n = @$rn; my$gd = scalar(@$rd); if ( scalar(@n) >=$gd ) {
my @q = ();
while ( scalar(@n) >= $gd ) { my$piv = $n[0]/$rd->[0];
push @q, $piv;$n[$_] -=$rd->[$_] *$piv foreach ( 0 .. min(scalar(@n), $gd)-1 ); shift @n; } return ( \@q, \@n ); } else { return ( [0],$rn );
}
}

sub poly_print
{
my @c = @_;
my $l = scalar(@c); for(my$i=0; $i <$l; $i++) { print$c[$i]; print "x^" . ($l-$i-1) . " + " if ($i < ($l-1)); } print "\n"; }  my ($q, $r); ($q, $r) = poly_long_div([1, -12, 0, -42], [1, -3]); poly_print(@$q);
poly_print(@$r); print "\n"; ($q, $r) = poly_long_div([1,-12,0,-42], [1,1,-3]); poly_print(@$q);
poly_print(@$r); print "\n"; ($q, $r) = poly_long_div([1,3,2], [1,1]); poly_print(@$q);
poly_print(@$r); print "\n"; # the example from the OCaml solution ($q, $r) = poly_long_div([1,-4,6,5,3], [1,2,1]); poly_print(@$q);
print.polynomial(r$r)  Racket  #lang racket (define (deg p) (for/fold ([d -inf.0]) ([(pi i) (in-indexed p)]) (if (zero? pi) d i))) (define (lead p) (vector-ref p (deg p))) (define (mono c d) (build-vector (+ d 1) (λ(i) (if (= i d) c 0)))) (define (poly*cx^n c n p) (vector-append (make-vector n 0) (for/vector ([pi p]) (* c pi)))) (define (poly+ p q) (poly/lin 1 p 1 q)) (define (poly- p q) (poly/lin 1 p -1 q)) (define (poly/lin a p b q) (cond [(< (deg p) 0) q] [(< (deg q) 0) p] [(< (deg p) (deg q)) (poly/lin b q a p)] [else (define ap+bq (for/vector #:length (+ (deg p) 1) #:fill 0 ([pi p] [qi q]) (+ (* a pi) (* b qi)))) (for ([i (in-range (+ (deg q) 1) (+ (deg p) 1))]) (vector-set! ap+bq i (* a (vector-ref p i)))) ap+bq])) (define (poly/ n d) (define N (deg n)) (define D (deg d)) (cond [(< N 0) (error 'poly/ "can't divide by zero")] [(< N D) (values 0 n)] [else (define c (/ (lead n) (lead d))) (define q (mono c (- N D))) (define r (poly- n (poly*cx^n c (- N D) d))) (define-values (q1 r1) (poly/ r d)) (values (poly+ q q1) r1)])) ; Example: (poly/ #(-42 0 -12 1) #(-3 1)) ; Output: '#(-27 -9 1) '#(-123 0)  REXX /* REXX needed by some... */ z='1 -12 0 -42' /* Numerator */ n='1 -3' /* Denominator */ zx=z nx=n copies('0 ',words(z)-words(n)) qx='' /* Quotient */ Do Until words(zx)<words(n) Parse Value div(zx,nx) With q zx qx=qx q nx=subword(nx,1,words(nx)-1) End Say '('show(z)')/('show(n)')=('show(qx)')' Say 'Remainder:' show(zx) Exit div: Procedure Parse Arg z,n q=word(z,1)/word(n,1) zz='' Do i=1 To words(z) zz=zz word(z,i)-q*word(n,i) End Return q subword(zz,2) show: Procedure Parse Arg poly d=words(poly)-1 res='' Do i=1 To words(poly) Select When d>1 Then fact='*x**'d When d=1 Then fact='*x' Otherwise fact='' End Select When word(poly,i)=0 Then p='' When word(poly,i)=1 Then p='+'substr(fact,2) When word(poly,i)=-1 Then p='-'substr(fact,2) When word(poly,i)<0 Then p=word(poly,i)||fact Otherwise p='+'word(poly,i)||fact End res=res p d=d-1 End Return strip(space(res,0),'L','+')  {{out}} (x**3-12*x**2-42)/(x-3)=(x**2-9*x-27) Remainder: -123  Ruby Implementing the algorithm given in the task description: def polynomial_long_division(numerator, denominator) dd = degree(denominator) raise ArgumentError, "denominator is zero" if dd < 0 if dd == 0 return [multiply(numerator, 1.0/denominator[0]), [0]*numerator.length] end q = [0] * numerator.length while (dn = degree(numerator)) >= dd d = shift_right(denominator, dn - dd) q[dn-dd] = numerator[dn] / d[degree(d)] d = multiply(d, q[dn-dd]) numerator = subtract(numerator, d) end [q, numerator] end def degree(ary) idx = ary.rindex(&:nonzero?) idx ? idx : -1 end def shift_right(ary, n) [0]*n + ary[0, ary.length - n] end def subtract(a1, a2) a1.zip(a2).collect {|v1,v2| v1 - v2} end def multiply(ary, num) ary.collect {|x| x * num} end f = [-42, 0, -12, 1] g = [-3, 1, 0, 0] q, r = polynomial_long_division(f, g) puts "#{f} / #{g} => #{q} remainder #{r}" # => [-42, 0, -12, 1] / [-3, 1, 0, 0] => [-27, -9, 1, 0] remainder [-123, 0, 0, 0] g = [-3, 1, 1, 0] q, r = polynomial_long_division(f, g) puts "#{f} / #{g} => #{q} remainder #{r}" # => [-42, 0, -12, 1] / [-3, 1, 1, 0] => [-13, 1, 0, 0] remainder [-81, 16, 0, 0]  Implementing the algorithms on the [[wp:Polynomial long division|wikipedia page]] -- uglier code but nicer user interface def polynomial_division(f, g) if g.length == 0 or (g.length == 1 and g[0] == 0) raise ArgumentError, "denominator is zero" elsif g.length == 1 [f.collect {|x| Float(x)/g[0]}, [0]] elsif g.length == 2 synthetic_division(f, g) else higher_degree_synthetic_division(f, g) end end def synthetic_division(f, g) board = [f] << Array.new(f.length) << Array.new(f.length) board[2][0] = board[0][0] 1.upto(f.length - 1).each do |i| board[1][i] = board[2][i-1] * -g[1] board[2][i] = board[0][i] + board[1][i] end [board[2][0..-2], [board[2][-1]]] end # an ugly mess of array index arithmetic # http://en.wikipedia.org/wiki/Polynomial_long_division#Higher_degree_synthetic_division def higher_degree_synthetic_division(f, g) # [use] the negative coefficients of the denominator following the leading term lhs = g[1..-1].collect {|x| -x} board = [f] q = [] 1.upto(f.length - lhs.length).each do |i| n = 2*i - 1 # underline the leading coefficient of the right-hand side, multiply it by # the left-hand coefficients and write the products beneath the next columns # on the right. q << board[n-1][i-1] board << Array.new(f.length).fill(0, i) # row n (lhs.length).times do |j| board[n][i+j] = q[-1]*lhs[j] end # perform an addition board << Array.new(f.length).fill(0, i) # row n+1 (lhs.length + 1).times do |j| board[n+1][i+j] = board[n-1][i+j] + board[n][i+j] if i+j < f.length end end # the remaining numbers in the bottom row correspond to the coefficients of the remainder r = board[-1].compact q = [0] if q.empty? [q, r] end f = [1, -12, 0, -42] g = [1, -3] q, r = polynomial_division(f, g) puts "#{f} / #{g} => #{q} remainder #{r}" # => [1, -12, 0, -42] / [1, -3] => [1, -9, -27] remainder [-123] g = [1, 1, -3] q, r = polynomial_division(f, g) puts "#{f} / #{g} => #{q} remainder #{r}" # => [1, -12, 0, -42] / [1, 1, -3] => [1, -13] remainder [16, -81]  Best of both worlds: {{trans|Tcl}} def polynomial_division(f, g) if g.length == 0 or (g.length == 1 and g[0] == 0) raise ArgumentError, "denominator is zero" end return [[0], f] if f.length < g.length q, n = [], f.dup while n.length >= g.length q << Float(n[0]) / g[0] n[0, g.length].zip(g).each_with_index do |pair, i| n[i] = pair[0] - q[-1] * pair[1] end n.shift end q = [0] if q.empty? n = [0] if n.empty? [q, n] end f = [1, -12, 0, -42] g = [1, -3] q, r = polynomial_division(f, g) puts "#{f} / #{g} => #{q} remainder #{r}" # => [1, -12, 0, -42] / [1, -3] => [1.0, -9.0, -27.0] remainder [-123.0] g = [1, 1, -3] q, r = polynomial_division(f, g) puts "#{f} / #{g} => #{q} remainder #{r}" # => [1, -12, 0, -42] / [1, 1, -3] => [1.0, -13.0] remainder [16.0, -81.0]  Sidef {{trans|Perl}} func poly_long_div(rn, rd) { var n = rn.map{_} var gd = rd.len if (n.len >= gd) { return(gather { while (n.len >= gd) { var piv = n[0]/rd[0] take(piv) { |i| n[i] -= (rd[i] * piv) } << ^(n.len min gd) n.shift } }, n) } return([0], rn) }  Example: func poly_print(c) { var l = c.len c.each_kv {|i, n| print n print("x^", (l - i - 1), " + ") if (i < l-1) } print "\n"; } var poly = [ Pair([1,-12,0,-42], [1, -3]), Pair([1,-12,0,-42], [1,1,-3]), Pair( [1,3,2], [1,1]), Pair( [1,-4,6,5,3], [1,2,1]), ] poly.each { |pair| var (q, r) = poly_long_div(pair.first, pair.second) poly_print(q) poly_print(r) print "\n" }  {{out}}  1x^2 + -9x^1 + -27 -123 1x^1 + -13 16x^1 + -81 1x^1 + 2 0 1x^2 + -6x^1 + 17 -23x^1 + -14  Slate define: #Polynomial &parents: {Comparable} &slots: {#coefficients -> ExtensibleArray new}. p@(Polynomial traits) new &capacity: n [ p cloneSettingSlots: #(coefficients) to: {p coefficients new &capacity: n} ]. p@(Polynomial traits) newFrom: seq@(Sequence traits) [ p clone >> [coefficients: (seq as: p coefficients). normalize. ] ]. p@(Polynomial traits) copy [ p cloneSettingSlots: #(coefficients) to: {p coefficients copy} ]. p1@(Polynomial traits) >= p2@(Polynomial traits) [p1 degree >= p2 degree]. p@(Polynomial traits) degree [p coefficients indexOfLastSatisfying: [| :n | n isZero not]]. p@(Polynomial traits) normalize [ [p degree isPositive /\ [p coefficients last isZero]] whileTrue: [p coefficients removeLast] ]. p@(Polynomial traits) * n@(Number traits) [ p newFrom: (p coefficients collect: [| :x | x * n]) ]. p@(Polynomial traits) / n@(Number traits) [ p newFrom: (p coefficients collect: [| :x | x / n]) ]. p1@(Polynomial traits) minusCoefficients: p2@(Polynomial traits) [ p1 newFrom: (p1 coefficients with: p2 coefficients collect: #- er) ]. p@(Polynomial traits) / denom@(Polynomial traits) [ p >= denom ifTrue: [| n q | n: p copy. q: p new. [n >= denom] whileTrue: [| piv | piv: p coefficients last / denom coefficients last. q coefficients add: piv. n: (n minusCoefficients: denom * piv). n normalize]. n coefficients isEmpty ifTrue: [n coefficients add: 0]. {q. n}] ifFalse: [{p newFrom: #(0). p copy}] ].  Smalltalk {{works with|GNU Smalltalk}} Object subclass: Polynomial [ |coeffs| Polynomial class >> new [ ^ super basicNew init ] init [ coeffs := OrderedCollection new. ^ self ] Polynomial class >> newWithCoefficients: coefficients [ |r| r := super basicNew. ^ r initWithCoefficients: coefficients ] initWithCoefficients: coefficients [ coeffs := coefficients asOrderedCollection. ^ self ] / denominator [ |n q| n := self deepCopy. self >= denominator ifTrue: [ q := Polynomial new. [ n >= denominator ] whileTrue: [ |piv| piv := (n coeff: 0) / (denominator coeff: 0). q addCoefficient: piv. n := n - (denominator * piv). n clean ]. ^ { q . (n degree) > 0 ifTrue: [ n ] ifFalse: [ n addCoefficient: 0. n ] } ] ifFalse: [ ^ { Polynomial newWithCoefficients: #( 0 ) . self deepCopy } ] ] * constant [ |r| r := self deepCopy. 1 to: (coeffs size) do: [ :i | r at: i put: ((r at: i) * constant) ]. ^ r ] at: index [ ^ coeffs at: index ] at: index put: obj [ ^ coeffs at: index put: obj ] >= anotherPoly [ ^ (self degree) >= (anotherPoly degree) ] degree [ ^ coeffs size ] - anotherPoly [ "This is not a real subtraction between Polynomial: it is an internal method ..." |a| a := self deepCopy. 1 to: ( (coeffs size) min: (anotherPoly degree) ) do: [ :i | a at: i put: ( (a at: i) - (anotherPoly at: i) ) ]. ^ a ] coeff: index [ ^ coeffs at: (index + 1) ] addCoefficient: coeff [ coeffs add: coeff ] clean [ [ (coeffs size) > 0 ifTrue: [ (coeffs at: 1) = 0 ] ifFalse: [ false ] ] whileTrue: [ coeffs removeFirst ]. ] display [ 1 to: (coeffs size) do: [ :i | (coeffs at: i) display. i < (coeffs size) ifTrue: [ ('x^%1 + ' % {(coeffs size) - i} ) display ] ] ] displayNl [ self display. Character nl display ] ].  |res| res := OrderedCollection new. res add: ((Polynomial newWithCoefficients: #( 1 -12 0 -42) ) / (Polynomial newWithCoefficients: #( 1 -3 ) )) ; add: ((Polynomial newWithCoefficients: #( 1 -12 0 -42) ) / (Polynomial newWithCoefficients: #( 1 1 -3 ) )). res do: [ :o | (o at: 1) display. ' with rest: ' display. (o at: 2) displayNl ]  SPAD {{works with|FriCAS}} {{works with|OpenAxiom}} {{works with|Axiom}} (1) -> monicDivide(x^3-12*x^2-42,x-3,'x) 2 (1) [quotient = x - 9x - 27,remainder = - 123] Type: Record(quotient: Polynomial(Integer),remainder: Polynomial(Integer))  Domain:[http://fricas.github.io/api/PolynomialCategory.html#l-polynomial-category-monic-divide] Tcl {{works with|Tcl|8.5 and later}} # poldiv - Divide two polynomials n and d. # Result is a list of two polynomials, q and r, where n = qd + r # and the degree of r is less than the degree of b. # Polynomials are represented as lists, where element 0 is the # x**0 coefficient, element 1 is the x**1 coefficient, and so on. proc poldiv {a b} { # Toss out leading zero coefficients efficiently while {[lindex$a end] == 0} {set a [lrange $a[set a {}] 0 end-1]} while {[lindex$b end] == 0} {set b [lrange $b[set b {}] 0 end-1]} if {[llength$a] < [llength $b]} { return [list 0$a]
}

# Rearrange the terms to put highest powers first
set n [lreverse $a] set d [lreverse$b]

# Carry out classical long division, accumulating quotient coefficients
# in q, and replacing n with the remainder.
set q {}
while {[llength $n] >= [llength$d]} {
set qd [expr {[lindex $n 0] / [lindex$d 0]}]
set i 0
foreach nd [lrange $n 0 [expr {[llength$d] - 1}]] dd $d { lset n$i [expr {$nd -$qd * $dd}] incr i } lappend q$qd
set n [lrange $n 1 end] } # Return quotient and remainder, constant term first return [list [lreverse$q] [lreverse $n]] } # Demonstration lassign [poldiv {-42. 0. -12. 1.} {-3. 1. 0. 0.}] Q R puts [list Q =$Q]
puts [list R = $R]  Ursala The input is a pair of lists of coefficients in order of increasing degree. Trailing zeros can be omitted. The output is a pair of lists (q,r), the quotient and remainder polynomial coefficients. This is a straightforward implementation of the algorithm in terms of list operations (fold, zip, map, distribute, etc.) instead of array indexing, hence not unnecessarily verbose. #import std #import flo polydiv = zeroid~-l~~; leql?rlX\~&NlX ^H\(@rNrNSPXlHDlS |\ :/0.) @NlX //=> ?( @lrrPX ==!| zipp0.; @x not zeroid+ ==@h->hr ~&t, (^lryPX/~&lrrl2C minus^*p/~&rrr times*lrlPD)^/div@bzPrrPlXO ~&, @r ^|\~& ~&i&& :/0.)  test program: #cast %eLW example = polydiv(<-42.,0.,-12.,1.>,<-3.,1.,0.,0.>)  output: ( <-2.700000e+01,-9.000000e+00,1.000000e+00>, <-1.230000e+02>)  VBA {{trans|Phix}} Option Base 1 Function degree(p As Variant) For i = UBound(p) To 1 Step -1 If p(i) <> 0 Then degree = i Exit Function End If Next i degree = -1 End Function Function poly_div(ByVal n As Variant, ByVal d As Variant) As Variant If UBound(d) < UBound(n) Then ReDim Preserve d(UBound(n)) End If Dim dn As Integer: dn = degree(n) Dim dd As Integer: dd = degree(d) If dd < 0 Then poly_div = CVErr(xlErrDiv0) Exit Function End If Dim quot() As Integer ReDim quot(dn) Do While dn >= dd Dim k As Integer: k = dn - dd Dim qk As Integer: qk = n(dn) / d(dd) quot(k + 1) = qk Dim d2() As Variant d2 = d ReDim Preserve d2(UBound(d) - k) For i = 1 To UBound(d2) n(UBound(n) + 1 - i) = n(UBound(n) + 1 - i) - d2(UBound(d2) + 1 - i) * qk Next i dn = degree(n) Loop poly_div = Array(quot, n) '-- (n is now the remainder) End Function Function poly(si As Variant) As String '-- display helper Dim r As String For t = UBound(si) To 1 Step -1 Dim sit As Integer: sit = si(t) If sit <> 0 Then If sit = 1 And t > 1 Then r = r & IIf(r = "", "", " + ") Else If sit = -1 And t > 1 Then r = r & IIf(r = "", "-", " - ") Else If r <> "" Then r = r & IIf(sit < 0, " - ", " + ") sit = Abs(sit) End If r = r & CStr(sit) End If End If r = r & IIf(t > 1, "x" & IIf(t > 2, t - 1, ""), "") End If Next t If r = "" Then r = "0" poly = r End Function Function polyn(s As Variant) As String Dim t() As String ReDim t(2 * UBound(s)) For i = 1 To 2 * UBound(s) Step 2 t(i) = poly(s((i + 1) / 2)) Next i t(1) = String$(45 - Len(t(1)) - Len(t(3)), " ") & t(1)
t(2) = "/"
t(4) = "="
t(6) = "rem"
polyn = Join(t, " ")
End Function

Public Sub main()
Dim tests(7) As Variant
tests(1) = Array(Array(-42, 0, -12, 1), Array(-3, 1))
tests(2) = Array(Array(-3, 1), Array(-42, 0, -12, 1))
tests(3) = Array(Array(-42, 0, -12, 1), Array(-3, 1, 1))
tests(4) = Array(Array(2, 3, 1), Array(1, 1))
tests(5) = Array(Array(3, 5, 6, -4, 1), Array(1, 2, 1))
tests(6) = Array(Array(3, 0, 7, 0, 0, 0, 0, 0, 3, 0, 0, 1), Array(1, 0, 0, 5, 0, 0, 0, 1))
tests(7) = Array(Array(-56, 87, -94, -55, 22, -7), Array(2, 0, 1))
Dim num As Variant, denom As Variant, quot As Variant, rmdr As Variant
For i = 1 To 7
num = tests(i)(1)
denom = tests(i)(2)
tmp = poly_div(num, denom)
quot = tmp(1)
rmdr = tmp(2)
Debug.Print polyn(Array(num, denom, quot, rmdr))
Next i
End Sub


{{out}}

                          x3 - 12x2 - 42 / x - 3 = x2 - 9x - 27 rem -123
x - 3 / x3 - 12x2 - 42 = 0 rem x - 3
x3 - 12x2 - 42 / x2 + x - 3 = x - 13 rem 16x - 81
x2 + 3x + 2 / x + 1 = x + 2 rem 0
x4 - 4x3 + 6x2 + 5x + 3 / x2 + 2x + 1 = x2 - 6x + 17 rem -23x - 14
x11 + 3x8 + 7x2 + 3 / x7 + 5x3 + 1 = x4 + 3x - 5 rem -16x4 + 25x3 + 7x2 - 3x + 8
-7x5 + 22x4 - 55x3 - 94x2 + 87x - 56 / x2 + 2 = -7x3 + 22x2 - 41x - 138 rem 169x + 220


zkl

fcn polyLongDivision(a,b){  // (a0 + a1x + a2x^2 + a3x^3 ...)
_assert_(degree(b)>=0,"degree(%s) < 0".fmt(b));
q:=List.createLong(a.len(),0.0);
q[z]=m;
d,a = d.apply('*(m)), a.zipWith('-,d);
}
return(q,a);		// may have trailing zero elements
}
fcn degree(v){  // -1,0,..len(v)-1, -1 if v==0
v.len() - v.copy().reverse().filter1n('!=(0)) - 1;
}
fcn polyString(terms){ // (a0,a1,a2...)-->"a0 + a1x + a2x^2 ..."
str:=[0..].zipWith('wrap(n,a){ if(a) "+ %sx^%s ".fmt(a,n) else "" },terms)
.pump(String)
.replace("x^0 "," ").replace(" 1x"," x").replace("x^1 ","x ")
.replace("+ -", "- ");
if(not str)     return(" ");  // all zeros
if(str[0]=="+") str[1,*];     // leave leading space
else            String("-",str[2,*]);
}

q,r:=polyLongDivision(T(-42.0, 0.0, -12.0, 1.0),T(-3.0, 1.0));
println("Quotient  = ",polyString(q));
println("Remainder = ",polyString(r));


{{out}}


Quotient  = -27 - 9x + x^2
Remainder = -123