322 lines
6 KiB
Perl
322 lines
6 KiB
Perl
package Minilisp;
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use strict;
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use warnings;
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use Data::Dumper;
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use constant {
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LPAREN => 1,
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RPAREN => 2,
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IDENT => 3,
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STRING => 4,
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NUMBER => 5,
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};
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sub tokenize {
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my $str = shift;
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my @tokens;
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$str =~ s/^\s+//;
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$str =~ s/\s+$//;
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while ($str)
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{
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if ($str =~ s/^\(//)
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{
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push @tokens, { type => LPAREN };
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}
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elsif($str =~ s/^\)//)
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{
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push @tokens, { type => RPAREN };
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}
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elsif($str =~ s/^"(([^"\\]|\\.)+)"//)
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{
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my $value = $1;
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my %special_chars = (
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'"' => '"',
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"n" => "\n",
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"t" => "\t",
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"\\" => "\\",
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);
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$value =~ s/\\(.)/$special_chars{$1}/eg;
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push @tokens, {
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type => STRING,
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value => $value,
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};
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}
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elsif($str =~ s/^([^\s()"]+)//)
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{
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my $ident = $1;
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if($ident =~ /^[0-9]+$/)
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{
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push @tokens, {
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type => NUMBER,
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value => 0+ $ident,
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};
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}
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else
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{
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push @tokens, {
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type => IDENT,
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value => $ident,
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};
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}
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}
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else
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{
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die "Unknown token: $str";
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}
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$str =~ s/^\s+//;
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$str =~ s/\s+$//;
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}
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return @tokens;
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}
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my %stdctx = (
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'add' => sub {
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my $sum = 0;
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$sum += $_ foreach (@_);
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return $sum;
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},
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'sub' => sub {
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my $sum = shift;
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$sum -= $_ foreach (@_);
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return $sum;
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},
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'print' => sub {
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my $e = shift;
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print "$e\n";
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return undef;
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},
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'eq' => sub { my ($a, $b) = @_; return ($a eq $b); },
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'ne' => sub { my ($a, $b) = @_; return ($a ne $b); },
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'==' => sub { my ($a, $b) = @_; return ($a == $b); },
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'!=' => sub { my ($a, $b) = @_; return ($a != $b); },
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'>' => sub { my ($a,$b) = @_; return ($a > $b); },
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'<' => sub { my ($a,$b) = @_; return ($a < $b); },
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'>=' => sub { my ($a,$b) = @_; return ($a >= $b); },
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'<=' => sub { my ($a,$b) = @_; return ($a <= $b); },
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'not' => sub { my ($a) = @_; return !$a; },
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't' => 1,
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'f' => 0,
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'nil' => undef,
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);
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sub parser {
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my @tokens = @_;
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my $expr = parser_expr(\@tokens);
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return sub {
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my $ctx = shift;
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my $ictx = { %stdctx, %$ctx };
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return $expr->($ictx);
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}
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}
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sub parser_expr {
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my $ts = shift;
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my $tok = shift @$ts;
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if ($tok->{type} == LPAREN)
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{
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return parser_call($ts);
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}
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elsif($tok->{type} == IDENT)
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{
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return sub {
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my $ctx = shift;
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my $name = $tok->{value};
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die "Undefined idnetifier $name" unless
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exists $ctx->{$name};
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return $ctx->{$name};
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}
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}
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elsif($tok->{type} == STRING || $tok->{type} == NUMBER)
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{
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return sub {
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return $tok->{value};
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}
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}
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else
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{
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die "Unexpected token $tok->{type}\n";
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}
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}
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my %macros;
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sub parser_call {
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my $ts = shift;
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if ($ts->[0]->{type} == IDENT)
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{
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my $name = $ts->[0]->{value};
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if (defined $macros{$name})
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{
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shift @$ts;
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return $macros{$name}->($ts);
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}
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}
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my $fn = parser_expr($ts);
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my @params;
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while ($ts->[0]->{type} != RPAREN)
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{
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push @params, parser_expr($ts);
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}
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my $tok = shift @$ts;
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die "Missing )" unless $tok->{type} == RPAREN;
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return sub {
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my $ctx = shift;
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my @p = map { $_->($ctx) } @params;
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$fn->($ctx)->(@p);
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};
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}
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sub macro_let {
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my $ts = shift;
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my $tok = shift @$ts;
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die "Expected ( after let" unless $tok->{type} == LPAREN;
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my $pctx = {};
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while ($ts->[0]->{type} != RPAREN)
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{
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my $ident = shift @$ts;
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die "Expected identifier in let" unless $ident->{type} == IDENT;
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my $assignment = parser_expr($ts);
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$pctx->{$ident->{value}} = $assignment;
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}
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$tok = shift @$ts;
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die "Expected ) after assignments in let" unless $tok->{type} == RPAREN;
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my $inner = parser_expr($ts);
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$tok = shift @$ts;
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die "Expected ) after let" unless $tok->{type} == RPAREN;
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return sub {
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my $octx = shift;
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my $ictx = { %$octx };
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$ictx->{$_} = $pctx->{$_}->($octx) foreach (keys %$pctx);
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return $inner->($ictx);
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}
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}
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$macros{let} = \¯o_let;
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sub macro_lambda {
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my $ts = shift;
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my $tok = shift @$ts;
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die "Expected ( after lambda keyword" unless $tok->{type} = LPAREN;
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my @param_list;
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while ($ts->[0]->{type} != RPAREN)
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{
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$tok = shift @$ts;
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die "Expected only identifier in parameter list" unless $tok->{type} == IDENT;
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push @param_list, $tok->{value};
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}
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$tok = shift @$ts;
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die "Expected ) after parameter list in lambda" unless $tok->{type} = LPAREN;
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my $body = parser_expr($ts);
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$tok = shift @$ts;
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die "Expected ) after lambda" unless $tok->{type} == RPAREN;
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return sub {
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my $octx = shift;
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return sub {
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my $ictx = { %$octx };
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my @pnames = @param_list;
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my @pvals = @_;
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while ( (my $name = shift @pnames) && (my $val = shift @pvals) )
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{
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$ictx->{$name} = $val;
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}
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die "Too many arguments" if scalar(@pvals);
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die "Not enough arguments" if scalar(@pnames);
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return $body->($ictx);
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}
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}
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}
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$macros{lambda} = \¯o_lambda;
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sub macro_if {
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my $ts = shift;
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print Dumper($ts);
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my $cond = parser_expr($ts);
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my $tbranch = parser_expr($ts);
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my $fbranch = parser_expr($ts);
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my $tok = shift @$ts;
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die "Expected ) after else expression" unless $tok->{type} == RPAREN;
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return sub {
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my $ctx = shift;
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my $condresult = $cond->($ctx);
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if ($condresult) {
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return $tbranch->($ctx);
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} else {
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return $fbranch->($ctx);
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}
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}
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}
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$macros{if} = \¯o_if;
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sub macro_progn {
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my $ts = shift;
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my @steps;
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while ($ts->[0]->{type} != RPAREN)
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{
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push @steps, parser_expr($ts);
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}
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return sub {
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my $ctx = shift;
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my $result = undef;
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$result = $_->($ctx) foreach (@steps);
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return $result;
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}
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}
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$macros{progn} = \¯o_progn;
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sub compile {
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my ($term) = @_;
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my @tokens = tokenize($term);
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my $parsed = parser(@tokens);
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return $parsed;
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}
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1;
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