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ftilmann / latexdiff

Compares two latex files and marks up significant differences between them. Releases on www.ctan.org and mirrors
GNU General Public License v3.0
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Incorrect handling of $$. #234

Open ITWOI opened 3 years ago

ITWOI commented 3 years ago

Hi,

Here is the latex code $=$$=$. You can see it can be split into two parts: $=$ and $=$. However, latexdiff mistakenly pairs the first $ and the last$, and tries to find the second $$.

I admit the code can be easily fixed by replacing the latex code with $==$, but maybe it may lead to other bugs.

ftilmann commented 3 years ago

It's a little bit pathological code, although of course technically correct. The easiest way to fix this would be to look for this pattern in pre-processing and make just the substitution you suggest. Would that be OK? - it would modify the .tex a little, so does not quite conform the ambition that the new file can be reconstructed from the diff'ed file. Is there ever a time, when this construction has its justification? Of course, latexdiff should cope with idiosyncratic but correct .tex It's easy enough to turn off detection for $$ entirely and would be theoretically justified as it's not strictly latex but original TeX. But I feel this would cause many more problems.

ITWOI commented 3 years ago

The pathological code can be easily fixed. Since it only occurs once, I have already fixed it.

It's easy enough to turn off detection for $$ entirely and would be theoretically justified as it's not strictly latex but original TeX. But I feel this would cause many more problems.

The reason for reporting this bug is that I think the way how latexdiff processes this kind of syntax is incorrect. $=$$=$ is an example, maybe there are other bug patterns.