Hi Daniel and everyone.
I am using gprolog 1.3.2 on Linux and I have this problem. In certain
circumstances, number_codes is raising an exception when it should
succeed. This only happens if:
* number_codes has a string matching a valid number as the 2nd arg and a
variable as the first
* number_codes is called in the exception handling clause of 'catch'
* the exception clause is executing because the goal of 'catch'
contained a read_term which caused a parse error
* the parse error was due to an unmatched double quote.
This example produces the bug. It looks like the read_term is producing
two errors, one of which hangs around and causes an exception in
number_codes. The string of codes converts to sin("foo).
catch(read_from_codes([115,105,110,40,34,102,111,111,41,47], Term),
Bug,
number_codes(G, [51,49])).
note that if you replace number_codes with name, the example executes
and catches the exception correctly, but G gets set to the atom '31'
rather than the number 31, which I guess is because the implementation
of name calls number_codes internally, and calls atom_codes when that
raises an exception.
Hope you enjoy this challenge!
--Jasper
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