27 lines
435 B
Plaintext
27 lines
435 B
Plaintext
|
|
|
|
###
|
|
### alternate-continuation
|
|
###
|
|
|
|
## Chapter 8 section 8.1
|
|
|
|
sub alternate {
|
|
my @p = @_;
|
|
return parser { return () } if @p == 0;
|
|
return $p[0] if @p == 1;
|
|
|
|
my $p;
|
|
$p = parser {
|
|
my ($input, $continuation) = @_;
|
|
for (@p) {
|
|
if (my ($v) = $_->($input, $continuation)) {
|
|
return $v;
|
|
}
|
|
}
|
|
return; # Failure
|
|
};
|
|
$N{$p} = "(" . join(" | ", map $N{$_}, @p) . ")";
|
|
return $p;
|
|
}
|