Algebra filter and negative numbers

Algebra filter and negative numbers

by Jennifer Cass -
Number of replies: 6

Hi-

I'm having trouble with inequalities that have negative numbers:

@@@x<>-2@@@, @@@x<=-2@@@ and @@@x>=-2@@@ all give @@x-2@@.

Any suggestions?

Thanks.

-Jennifer

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In reply to Jennifer Cass

Re: Algebra filter and negative numbers

by Zbigniew Fiedorowicz -
Sorry, it's a bug.  I'll try to fix it tomorrow.  In the meantime, a workaround would be to write the inequalities backwards: @@@-2<>x@@@ ==> @@-2<>x@@ etc.  Another workaround would be to use the debugging script http://yourmoodlesite/filter/algebra/algebradebug.php, enter the expression without the negative sign, click on "Second Stage Tex Translation", put the minus sign there, and then enter the resulting expression in TeX syntax:
x<= 2   -----> x \leq 2  ----> x \leq -2 ----> $$$x\leq -2$$$ ----> $$x \leq -2$$
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In reply to Jennifer Cass

Re: Algebra filter and negative numbers

by Zbigniew Fiedorowicz -
I've put a bug fix for this problem in the cvs.  The files affected are
  • filter/algebra/filter.php
  • filter/algebra/AlgParser.pm
  • filter/algebra/algebradebug.php
You will need to use the algebradebug.php script to delete the cache database entries for any expressions which were processed by the previous buggy versions of the algebra filter.php
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In reply to Zbigniew Fiedorowicz

Odp: Re: Algebra filter and negative numbers

by Łukasz Sanokowski -
I have a problem with negative numbers used in lim parameters. When for example variable in base (I'm not sure if i name this correctly in english) goes to negative number, the algebra filter display it incorrectly. Example:

lim((x^3-3x^2+2)/(x^2-4),x,-7) displays as @@lim((x^3-3x^2+2)/(x^2-4),x,-7)@@

After removing minus sing from number "7" algebra filter display it correctly.

Thanks in advance for response.
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In reply to Łukasz Sanokowski

Re: Odp: Re: Algebra filter and negative numbers

by Mauno Korpelainen -

Why not use Tex or Asciimathml instead of Algebra filter that has a very limited subset of commands you can use in Tex. For example

\lim_{x\to{-7}}\frac{x^3-3x^2+2}{x^2-4} between double dollars

gives

$$\lim_{x\to{-7}}\frac{x^3-3x^2+2}{x^2-4}$$
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