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FTE: Bug in the regular expression compiler

Dear People

I shall issue a reportbug, but I wanted to communicate with you more directly.
The test suite of regular expressions which the upstream author of FTE used
did not test properly one of the properties of the regular expression compiler. It is true that it will successfully deal with the regular expression "{a|b|c|d|e}",
but it will NOT deal with "{ab|cd|ef|gh}". The only way to match alternative
strings which are more than one character long is to put each one between
braces: "{ab}|{cd}|{ef}".

I used the regular expression compiler and matcher code from FTE as the
basis of my Unicode regular expression library for use with Algol 68 programs. The code for the compiler is the same except that sets are specified differently.
The code for the matcher is more or less the same.

I have had to document the above compiler error as a feature of the library.
I did check with a working binary of xfte and discovered that the editor would
not search for alternative strings as described above.


Sian Mountbatten
Algol 68 Specialist

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