Unexpected results of some expressions about math-parser HOT 10 CLOSED

Ok, that's a little weird, I will look into it.

0*log(0) should certainly return NAN or possibly throw an exception. As a mathematician, I prefer to leave 0^0 undefined, even though I realize that 0^0=1 is often a useful convention.

(It's not hard to write a custom Evaluator making sure 0^0 returns 1, though.)

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@byCedric Thank you for the report, I think that should fix it.

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@byCedric Looking forward to it!

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Haha, I will never force a mathematician to some common conventions. Thanks for the tip on creating a custom evaluator, will definitely look into it. If I can help, you can message me anytime. Again, thanks for this library and your quick response!

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I had a look at the 0*log(0) issue. It is due to some slightly overaggressive simplification in the parser. I will think of how to fix this without losing some simplifications that I'd like to keep, but it might take a few days.

In the meantime (and for your use case, it won't hurt much), try

$parser = new StdMathParser(); // or RationalMathParser if you prefer
$parser->setSimplifying(false);

and 0*log(0) will evaluate to NAN as expected.

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Actually, with setSimplifying(false), you will also get 0^0 = 1 for free.

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You are the best! If I can help you on something, you can always message me. Thanks you once again for your quick response and good workarounds!

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I don't know if this is related or if I should open up a new issue. Right now we have an exception (non math-exception) being thrown when the expression !1 is being evaluated.

With version 1.2.3 this threw an UnknownTokenException: Unknown token 0 encountered in Lexing/Lexer.php on line 85 which is correct. But as of 1.3.3 a Uncaught Error: Call to a member function accept() on null in Interpreting/Evaluator.php:186 is being thrown. I briefly tried to find the cause, but I'm still searching.

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This doesn't seem to be related. 1.3.0 added support for factorials, so "!1" shouldn't throw a UnknownTokenException, but it should throw a SyntaxErrorException instead. It seems like some malformed expressions containing ! slips through the Parser. I'll check it out.

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Thank you once again for your quick fix! If you are ever visiting Amsterdam I will buy you a beer or something!

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