perl6/step2_eval.pl

   1 use v6;
   2 use lib IO::Path.new($?FILE).dirname;
   3 use reader;
   4 use printer;
   5 use types;
   6
   7 sub read ($str) {
   8   return read_str($str);
   9 }
  10
  11 sub eval_ast ($ast, $env) {
  12   given $ast {
  13     when MalSymbol  { $env{$ast.val} || die X::MalNotFound.new(name => $ast.val) }
  14     when MalList    { MalList([$ast.map({ eval($_, $env) })]) }
  15     when MalVector  { MalVector([$ast.map({ eval($_, $env) })]) }
  16     when MalHashMap { MalHashMap($ast.kv.map({ $^a => eval($^b, $env) }).Hash) }
  17     default         { $ast // $NIL }
  18   }
  19 }
  20
  21 sub eval ($ast, $env) {
  22   return eval_ast($ast, $env) if $ast !~~ MalList;
  23   return $ast if !$ast.elems;
  24
  25   my ($func, @args) = eval_ast($ast, $env).val;
  26   my $arglist = MalList(@args);
  27   return $func.apply($arglist);
  28 }
  29
  30 sub print ($exp) {
  31   return pr_str($exp, True);
  32 }
  33
  34 my $repl_env;
  35
  36 sub rep ($str) {
  37   return print(eval(read($str), $repl_env));
  38 }
  39
  40 sub MAIN {
  41   $repl_env<+> = MalCode({ MalNumber($^a[0].val + $^a[1].val) });
  42   $repl_env<-> = MalCode({ MalNumber($^a[0].val - $^a[1].val) });
  43   $repl_env<*> = MalCode({ MalNumber($^a[0].val * $^a[1].val) });
  44   $repl_env</> = MalCode({ MalNumber(($^a[0].val / $^a[1].val).Int) });
  45
  46   while (my $line = prompt 'user> ').defined {
  47     say rep($line);
  48     CATCH {
  49       when X::MalException { .Str.say }
  50     }
  51   }
  52 }