Talk:Brace expansion: Difference between revisions
→Duplicate supression
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== Duplicate supression ==
The task currently has an ambiguity - specifically an explicit reference to an implementation (perl 6) which implements a requirement which is not explicitly stated in the task description.
More specifically, the perl 6 implementation suppresses duplicate results despite no description of this mechanism in the current task description. Consider {a,a,b} as an example which would generate duplicates. This issue shows up in the test case '{,{,gotta have{ ,\, again\, }}more }cowbell!' where nested empty prefixes appear. This case should have eight expansions. You can easily see this by placing a letter to the left of each non-escaped comma.
This means either the task description is buggy or the reference implementation is buggy.
:Well, I believe the task actually refers to the Perl (5) implementation, not the Perl 6 one. But leaving that aside, there's no duplicate suppression taking place here. Note what happens when I run these (through the Perl 6 version):
<pre>{X,{Y,gotta have{ ,\, again\, }}more }cowbell!
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:: That's a good point, that brace expansion should be only relevant in the surrounding context where it appears. So that's my bug and hopefully I can find it now. Thank you. --~~
:: Actually... after thinking about this further... I still think it's a problem.
:: Let's take aa{,{,11}cc}22 - we expand the inner braces and get aa{,cc}22 and aa{,11cc}22. This should then expand into aa22 aacc22 aa22 and aa11cc22. It seems to me that doing otherwise violates the specification that the inner brace be expanded first. Thoughts? Thanks. --[[User:Rdm|Rdm]] ([[User talk:Rdm|talk]]) 20:39, 31 January 2014 (UTC)
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