perl/step0_repl.pl


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use strict;
use warnings FATAL => qw(all);
use File::Basename;
use lib dirname (__FILE__);
use readline qw(mal_readline);

# read
sub READ {
    my $str = shift;
    return $str;
}

# eval
sub EVAL {
    my($ast, $env) = @_;
    return $ast;
}

# print
sub PRINT {
    my $exp = shift;
    return $exp;
}

# repl
sub REP {
    my $str = shift;
    return PRINT(EVAL(READ($str), {}));
}

while (1) {
    my $line = mal_readline("user> ");
    if (! defined $line) { last; }
    print(REP($line), "\n");
}