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COMMENT This routine is used in more then one place, and is essentially a template that can by used for many different types, eg INT, LONG INT... USAGE MODE SORTSTRUCT = INT, LONG INT, STRUCT(STRING name, addr) etc OP < = (SORTSTRUCT a,b)BOOL: ~;
PR READ "prelude/sort.a68" PR; [3]SORTSTRUCT list := (a,b,c); print((in place shell sort(list), new line)) END COMMENT
PROC in place shell sort = (REF FLEX []SORTSTRUCT seq)REF[]SORTSTRUCT:( INT inc := ( UPB seq + LWB seq + 1 ) OVER 2; WHILE inc NE 0 DO FOR index FROM LWB seq TO UPB seq DO INT i := index; SORTSTRUCT el = seq[i]; WHILE ( i - LWB seq >= inc | NOT(seq[i - inc] < el) | FALSE ) DO seq[i] := seq[i - inc]; i -:= inc OD; seq[i] := el OD; inc := IF inc = 2 THEN 1 ELSE ENTIER(inc * 5 / 11) FI OD; seq );
PROC in place shell sort reverse = (REF FLEX []SORTSTRUCT seq)REF[]SORTSTRUCT:(
INT inc := ( UPB seq + LWB seq + 1 ) OVER 2;
WHILE inc NE 0 DO
FOR index FROM LWB seq TO UPB seq DO
INT i := index;
SORTSTRUCT el = seq[i];
WHILE ( i - LWB seq >= inc | seq[i - inc] < el | FALSE ) DO
seq[i] := seq[i - inc];
i -:= inc
OD;
seq[i] := el
OD;
inc := IF inc = 2 THEN 1 ELSE ENTIER(inc * 5 / 11) FI
OD;
seq
);
SKIP