perl/step1_read_print.pl


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use strict;
use warnings FATAL => qw(all);
use readline qw(mal_readline);
use feature qw(switch);

use reader;
use printer;

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

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

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

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

while (1) {
    my $line = mal_readline("user> ");
    if (! defined $line) { last; }
    do {
        local $@;
        my $ret;
        eval {
            use autodie; # always "throw" errors
            print(REP($line), "\n");
            1;
        } or do {
            my $err = $@;
            given (ref $err) {
                when (/^BlankException/) {
                    # ignore and continue
                }
                default {
                    chomp $err;
                    print "Error: $err\n";
                }
            }
        };
    };
}