Perl: add step5_tco

[jackhill/mal.git] / perl / step5_tco.pl

use strict;
use warnings FATAL => qw(all);
use readline qw(readline);
use feature qw(switch);
use Data::Dumper;

use types qw($nil $true $false);
use reader;
use printer;
use env;
use core qw($core_ns);

# read
sub READ {
    my $str = shift;
    return reader::read_str($str);
}

# eval
sub eval_ast {
    my($ast, $env) = @_;
    given (ref $ast) {
        when (/^Symbol/) {
            $env->get($$ast);
        }
        when (/^List/) {
            my @lst = map {EVAL($_, $env)} @$ast;
            return List->new(\@lst);
        }
        default {
            return $ast;
        }
    }
}

sub EVAL {
    my($ast, $env) = @_;

    while (1) {

    #print "EVAL: " . printer::_pr_str($ast) . "\n";
    if (! ((ref $ast) =~ /^List/)) {
        return eval_ast($ast, $env);
    }

    # apply list
    my ($a0, $a1, $a2, $a3) = @$ast;
    given ((ref $a0) =~ /^Symbol/ ? $$a0 : $a0) {
        when (/^def!$/) {
            my $res = EVAL($a2, $env);
            return $env->set($$a1, $res);
        }
        when (/^let\*$/) {
            my $let_env = Env->new($env);
            for(my $i=0; $i < scalar(@{$a1}); $i+=2) {
                $let_env->set(${$a1->[$i]}, EVAL($a1->[$i+1], $let_env));
            }
            return EVAL($a2, $let_env);
        }
        when (/^do$/) {
            eval_ast($ast->slice(1, $#{$ast}-1), $env);
            $ast = $ast->[$#{$ast}];
        }
        when (/^if$/) {
            my $cond = EVAL($a1, $env);
            if ($cond eq $nil || $cond eq $false) {
                $ast = $a3 ? $a3 : $nil;
            } else {
                $ast = $a2;
            }
        }
        when (/^fn\*$/) {
            return Function->new(\&EVAL, $a2, $env, $a1);
        }
        default {
            my $el = eval_ast($ast, $env);
            my $f = $el->[0];
            if ((ref $f) =~ /^Function/) {
                $ast = $f->{ast};
                $env = $f->gen_env($el->rest());
            } else {
                return &{ $f }($el->rest());
            }
        }
    }

    } # TCO while loop
}

# print
sub PRINT {
    my $exp = shift;
    return printer::_pr_str($exp);
}

# repl
my $repl_env = Env->new();
sub REP {
    my $str = shift;
    return PRINT(EVAL(READ($str), $repl_env));
}

# core.pl: defined using perl
foreach my $n (%$core_ns) { $repl_env->set($n, $core_ns->{$n}); }

# core.mal: defined using the language itself
REP("(def! not (fn* (a) (if a false true)))");

while (1) {
    my $line = readline("user> ");
    if (! defined $line) { last; }
    eval {
        use autodie; # always "throw" errors
        print(REP($line), "\n");
        1;
    }; 
    if (my $err = $@) {
        chomp $err;
        print "Error: $err\n";
    }
}