perl/step7_quote.pl

   1 use strict;
   2 use warnings FATAL => qw(all);
   3 use readline qw(readline);
   4 use feature qw(switch);
   5 use Data::Dumper;
   6
   7 use types qw($nil $true $false _sequential_Q _symbol_Q);
   8 use reader;
   9 use printer;
  10 use env;
  11 use core qw($core_ns);
  12
  13 # read
  14 sub READ {
  15     my $str = shift;
  16     return reader::read_str($str);
  17 }
  18
  19 # eval
  20 sub is_pair {
  21     my ($x) = @_;
  22     return _sequential_Q($x) && scalar(@$x) > 0;
  23 }
  24
  25 sub quasiquote {
  26     my ($ast) = @_;
  27     if (!is_pair($ast)) {
  28         return List->new([Symbol->new("quote"), $ast]);
  29     } elsif (_symbol_Q($ast->[0]) && ${$ast->[0]} eq 'unquote') {
  30         return $ast->[1];
  31     } elsif (is_pair($ast->[0]) && _symbol_Q($ast->[0][0]) &&
  32              ${$ast->[0][0]} eq 'splice-unquote') {
  33         return List->new([Symbol->new("concat"),
  34                           $ast->[0][1],
  35                           quasiquote($ast->rest())]);
  36     } else {
  37         return List->new([Symbol->new("cons"),
  38                           quasiquote($ast->[0]),
  39                           quasiquote($ast->rest())]);
  40     }
  41 }
  42
  43 sub eval_ast {
  44     my($ast, $env) = @_;
  45     given (ref $ast) {
  46         when (/^Symbol/) {
  47             $env->get($$ast);
  48         }
  49         when (/^List/) {
  50             my @lst = map {EVAL($_, $env)} @$ast;
  51             return List->new(\@lst);
  52         }
  53         default {
  54             return $ast;
  55         }
  56     }
  57 }
  58
  59 sub EVAL {
  60     my($ast, $env) = @_;
  61
  62     while (1) {
  63
  64     #print "EVAL: " . printer::_pr_str($ast) . "\n";
  65     if (! ((ref $ast) =~ /^List/)) {
  66         return eval_ast($ast, $env);
  67     }
  68
  69     # apply list
  70     my ($a0, $a1, $a2, $a3) = @$ast;
  71     given ((ref $a0) =~ /^Symbol/ ? $$a0 : $a0) {
  72         when (/^def!$/) {
  73             my $res = EVAL($a2, $env);
  74             return $env->set($$a1, $res);
  75         }
  76         when (/^let\*$/) {
  77             my $let_env = Env->new($env);
  78             for(my $i=0; $i < scalar(@{$a1}); $i+=2) {
  79                 $let_env->set(${$a1->[$i]}, EVAL($a1->[$i+1], $let_env));
  80             }
  81             return EVAL($a2, $let_env);
  82         }
  83         when (/^quote$/) {
  84             return $a1;
  85         }
  86         when (/^quasiquote$/) {
  87             return EVAL(quasiquote($a1), $env);
  88         }
  89         when (/^do$/) {
  90             eval_ast($ast->slice(1, $#{$ast}-1), $env);
  91             $ast = $ast->[$#{$ast}];
  92         }
  93         when (/^if$/) {
  94             my $cond = EVAL($a1, $env);
  95             if ($cond eq $nil || $cond eq $false) {
  96                 $ast = $a3 ? $a3 : $nil;
  97             } else {
  98                 $ast = $a2;
  99             }
 100         }
 101         when (/^fn\*$/) {
 102             return Function->new(\&EVAL, $a2, $env, $a1);
 103         }
 104         default {
 105             my $el = eval_ast($ast, $env);
 106             my $f = $el->[0];
 107             if ((ref $f) =~ /^Function/) {
 108                 $ast = $f->{ast};
 109                 $env = $f->gen_env($el->rest());
 110             } else {
 111                 return &{ $f }($el->rest());
 112             }
 113         }
 114     }
 115
 116     } # TCO while loop
 117 }
 118
 119 # print
 120 sub PRINT {
 121     my $exp = shift;
 122     return printer::_pr_str($exp);
 123 }
 124
 125 # repl
 126 my $repl_env = Env->new();
 127 sub REP {
 128     my $str = shift;
 129     return PRINT(EVAL(READ($str), $repl_env));
 130 }
 131
 132 # core.pl: defined using perl
 133 foreach my $n (%$core_ns) { $repl_env->set($n, $core_ns->{$n}); }
 134 $repl_env->set('eval', sub { EVAL($_[0][0], $repl_env); });
 135 my @_argv = map {String->new($_)}  @ARGV[1..$#ARGV];
 136 $repl_env->set('*ARGV*', List->new(\@_argv));
 137
 138 # core.mal: defined using the language itself
 139 REP("(def! not (fn* (a) (if a false true)))");
 140 REP("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))");
 141
 142 if ($#ARGV > 0) {
 143     REP("(load-file \"" . $ARGV[0] . "\")");
 144     exit 0;
 145 }
 146 while (1) {
 147     my $line = readline("user> ");
 148     if (! defined $line) { last; }
 149     eval {
 150         use autodie; # always "throw" errors
 151         print(REP($line), "\n");
 152         1;
 153     };
 154     if (my $err = $@) {
 155         chomp $err;
 156         print "Error: $err\n";
 157     }
 158 }