perl/step1_read_print.pl

   1 use strict;
   2 use warnings;
   3 use readline qw(readline);
   4 use feature qw(switch);
   5
   6 use reader;
   7 use printer;
   8
   9 # read
  10 sub READ {
  11     my $str = shift;
  12     return reader::read_str($str);
  13 }
  14
  15 # eval
  16 sub EVAL {
  17     my($ast, $env) = @_;
  18     return $ast;
  19 }
  20
  21 # print
  22 sub PRINT {
  23     my $exp = shift;
  24     return printer::_pr_str($exp);
  25 }
  26
  27 # repl
  28 sub REP {
  29     my $str = shift;
  30     return PRINT(EVAL(READ($str), {}));
  31 }
  32
  33 while (1) {
  34     my $line = readline("user> ");
  35     if (! defined $line) { last; }
  36     eval {
  37         use autodie; # always "throw" errors
  38         print(REP($line), "\n");
  39         1;
  40     };
  41     if (my $err = $@) {
  42         chomp $err;
  43         print "Error: $err\n";
  44     }
  45 }