⚠️ Warning: This is a draft ⚠️

This means it might contain formatting issues, incorrect code, conceptual problems, or other severe issues.

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{{implementation|HQ9+}}{{collection|RCHQ9+}} [[User:Kevin Reid|The original author of this example]] (written in [[E]]) would like to note the following deficiencies in [http://www.cliff.biffle.org/esoterica/hq9plus.html the HQ9+ specification]:

  • The treatment of unrecognized characters other than whitespace is unspecified. However, the only implementation provided, in [[OCaml]], rejects them, so this implementation also does. Additionally, rejecting unknown characters ensures that the compiler will not incorrectly compile [[HQ9+]] programs using future extensions.
  • While the given "qqqq" example implies that whitespace (specifically, trailing newlines) is permissible and that operation codes are case-insensitive, neither of these are explicitly stated.
  • The initial value of the accumulator is unspecified. This implementation has chosen 11472, which is of course the value such that executing the HQ9+ program "HQ9+" will result in the accumulator having a value equal to the length of the program's output.

```e>def makeSeqExpr := def makeLiteralExpr := elang:evm.makeLiteralExpr def eParser := elang:syntax.makeEParser

the extra $ protects this as an RC example by breaking up the close tag

def `@_

@beerSource</la${""}ng>@_` :=
def beerProgram := eParser(beerSource)

def opcodes := [
  'H' => def h := e`stdout.println("Hello, World!")`,
  'Q' => def q := e`stdout.println(mySource)`,
  '9' =>          e`{ def println := stdout.println; $beerProgram }`,
  '+' =>          e`::"the accumulator" += 1`,
  'h' => h,
  'q' => q,

/** HQ9+ compiler.
    The provided program is compiled into a function taking the output stream as an argument. */
def ::"RCHQ9+"(program :String) {
  return e`
    def ::"RCHQ9+ program"(stdout) {
      def mySource := ${makeLiteralExpr(null, program, null)}
      var ::"the accumulator" := 11472
        var exprs := []
        for ch ? (E.toString(ch) =~ rx`\S`) in program {
          exprs with= opcodes.fetch(ch, fn {
            throw(`Unrecognized HQ9+ opcode: $ch`)
        makeSeqExpr(null, exprs, null)
  # Maintenance note: Do not change this from safeScope without considering
  # the consequences as the beerProgram is incorporated from a wiki source
  # over unsecured HTTP.