Parse using Skip with a range

[jmatro]

As I understand the docs, it seems like

    parse "axxb" ["a" 1 3 skip "b"]

should return True -- "a", followed by 1 to 3 characters (of any value) that we will skip, followed by "b".
But it returns False.

Note that

    parse "axx" ["a" 1 3 skip end]

    parse "axxb" ["a" 1 3 "x" "b"]

each return True.

Comments welcome.

Thanks.

[Gabriele]

PARSE does not automatically backtrack. This means that 1 3 skip will always skip 3 characters (unless the string is shorter), independently of what follows it. PARSE is not a pattern matcher, but a grammar parser.

Depending on what you need exactly, there are various ways to express it as a grammar. For your simple example, one way is:

Code:

>> non-b: complement charset "b"
== make bitset! #{
FFFFFFFFFFFFFFFFFFFFFFFFFBFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
}
>> parse "axxb" ["a" 1 3 non-b "b"]
== true

[jmatro]

The light bulb just clicked on - thanks again.