It's cool that Rebol's PARSE dialect is generalized enough that it can do pattern matching and extraction on symbolic structures as well as on strings. Like this:
; match a single "a" character, followed by an开发者_如何转开发y number of "b" chars
>> string-rule: ["a" some "b"]
>> parse "abb" string-rule
== true
>> parse "aab" string-rule
== false
; look for a single apple symbol, followed by any number of bananas
>> block-rule: ['apple some 'banana]
>> parse [apple banana banana] block-rule
== true
>> parse [apple apple banana] block-rule
== false
But let's say I'm looking for a block containing an apple symbol, and then any number of character strings matching the string-rule
:
; test 1
>> parse [apple "ab" "abbbbb"] mixed-rule
== true
; test 2
>> parse [apple "aaaa" "abb"] mixed-rule
== false
; test 3
>> parse [banana "abb" "abbb"] mixed-rule
== false
How would I formulate such a mixed-rule
? Looking at the documentation it suggests that one can use INTO:
http://www.rebol.net/wiki/Parse_Project#INTO
The seemingly natural answer doesn't seem to work:
>> mixed-rule: ['apple some [string! into ["a" some "b"]]]
While it passes test 1 and correctly returns false for test 3, it incorrectly returns true in test 2. Is this my mistake or a bug in Rebol (I'm using r3 A111)?
Steeve over on the REBOL3 forum suggests this:
only the second string is checked.
Should be:
['apple some [and string! into ["a" some "b" ]]]
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