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package Interpreter;
# Here's the interpreter for a list of APIs. This is the guts of
# pattern matching.
use strict;
use warnings;
use feature 'say';
use Function::Parameters;
use Data::Dumper;
use Exporter;
our @ISA = qw(Exporter);
our @EXPORT_OK = qw(interprete); # Export on demand
use lib qw(.);
use API;
use PosExpr;
my $debug = 0;
sub setdebug { my($d) = @_; $debug = $d; }
#
# my $ok = runAt( $s, $lit, $at, $poshash, $name );
# Try to match $lit in $s at $at. Return 0 if we can't
# find that literal. 1 otherwise (and store name==pos in the poshash)
#
fun runAt( $s, $lit, $at, $poshash, $name )
{
my $pos = $at->eval($poshash);
return 0 unless substr($s,$pos,length($lit)) eq $lit;
$poshash->{$name} = $pos;
say "debug: A: set pos[$name] = $pos" if $debug;
return 1;
}
#
# my @litpos = findliteral( $lit, $p, $s );
# Find all instances of $lit atorafter position $p in $s,
# build and return a list of possible starting positions.
#
fun findliteral( $lit, $p, $s )
{
my $slen = length($s);
my $llen = length($lit);
my @result = grep { substr($s,$_,$llen) eq $lit; } $p..$slen-1;
#die "findliteral: lit=$lit, s=$s, results=".Dumper(\@result);
return @result;
}
#
# my $ok = runMatch( $s, $lit, $atorafter, $poshash, $name, $restapi, $mtlist );
# Try to find $lit in $s at-or-after position $atorafter. Return 0 if we
# can't find that literal anywhere. For each position location that
# literal does occur at, try each one in turn - running the whole of the
# rest of the API list @$restapi against each one. Return 1 if any one
# of them leads to an overall match.
# So: 0==fail. 1==stop interpreter.
#
fun runMatch( $s, $lit, $atorafter, $poshash, $name, $restapi, $mtlist )
{
$atorafter = $atorafter->eval($poshash);
my @litpos = findliteral( $lit, $atorafter, $s );
return 0 if @litpos==0;
# must try each possible position in @litpos in turn
say "debug: M: try each pos ".join(',',@litpos) if $debug;
foreach my $pos (@litpos)
{
$poshash->{$name} = $pos;
say "debug: try pos[$name] = $pos" if $debug;
my $match = interprete( $s, $restapi, $poshash, $mtlist );
say "debug: matchrest = $match" if $debug;
return 1 if $match;
undef $poshash->{$name};
}
return 0;
}
#
# my $ok = runTest( $pe1, $op, $pe2, $poshash );
# Perform a simple test: Evaluate both PosExprs $pe1 and $pe2
# down to numeric values, then compare those values via the
# operator $op ('>', '=' or '>=').
# Return 1 iff $pe1 ($op) $pe2. 0 otherwise.
#
fun runTest( $pe1, $op, $pe2, $poshash )
{
my $pv1 = $pe1->eval($poshash);
my $pv2 = $pe2->eval($poshash);
return 0 if $op eq '>' && $pv1 <= $pv2;
return 0 if $op eq '>=' && $pv1 < $pv2;
return 0 if $op eq '=' && $pv1 != $pv2;
return 1;
}
#
# my $cap = runCapture( $s, $pefrom, $peto, $poshash, $mtlist );
# Capture a portion of $s and push it onto @$mtlist.
# Evaluate $pefrom and $peto to numeric values $f and $t,
# then extract the substring of $s from $f, to $t, and
# then push that substring onto @$mtlist. Also return that
# same substring.
#
fun runCapture( $s, $pefrom, $peto, $poshash, $mtlist )
{
my $from = $pefrom->eval($poshash);
my $to = $peto->eval($poshash);
my $cap = substr($s,$from,$to-$from+1) // '';
push @$mtlist, $cap;
return $cap;
}
#
# my $match = interprete( $s, $apilist, $poshash, $mtlist );
# Interprete @$apilist against the string $s, using (and modifying)
# %$poshash which maps names to their positions.
# Return 1 for a match (filling in @$mtlist) or 0 for no match.
#
fun interprete( $s, $apilist, $poshash, $mtlist )
{
my $slen = length($s);
my $n = 0;
foreach my $api (@$apilist)
{
my $kind = $api->kind;
if( $kind eq 'A' ) # Match at pos
{
my( $lit, $at, $name ) = $api->A;
return 0 unless runAt( $s, $lit, $at, $poshash, $name );
}
elsif( $kind eq 'M' ) # Match at or after - tricky
{
my( $lit, $atorafterpos, $name ) = $api->M;
# Build the rest of the api list..
my @restapi = @$apilist[$n+1..$#$apilist];
my $ok = runMatch( $s, $lit, $atorafterpos,
$poshash, $name, \@restapi, $mtlist );
return $ok; #.. if $ok < 2;
}
elsif( $kind eq 'T' )
{
my( $pe1, $op, $pe2 ) = $api->T;
my $ok = runTest( $pe1, $op, $pe2, $poshash );
return 0 unless $ok;
say "debug: test $api succeeded" if $debug;
}
elsif( $kind eq 'C' )
{
my ($pe1, $pe2) = $api->C;
my $mn = @$mtlist;
my $cap = runCapture( $s, $pe1, $pe2, $poshash, $mtlist );
say "debug: C: set mt[$mn] to $cap" if $debug;
}
else
{
die "interprete: not yet implemented $kind\n";
}
$n++;
}
return 1;
}
1;
|
