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Perl for calculating an expression.
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Subject Author Date
Perl for calculating an expression. syang8 07-23-2008
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Posted by syang8 on July 23, 2008, 12:36 am
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 Is there any peal script available that I can quickly calculate a
string " (3+5)*5/40 " or " 4*7-7*(4+5) " ? There are only the digits
and +,-,*,/ and () available in the string. Thank you!

-Steve

Posted by Leon Timmermans on July 23, 2008, 6:40 am
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 On Tue, 22 Jul 2008 21:36:26 -0700, syang8 wrote:

> Is there any peal script available that I can quickly calculate a string
> " (3+5)*5/40 " or " 4*7-7*(4+5) " ? There are only the digits and
> +,-,*,/ and () available in the string. Thank you!
>
> -Steve

Look up Dijkstra's shunting yard algorithm. It's quite easy to implement.

Leon Timmermans

Posted by Glenn Jackman on July 23, 2008, 10:06 am
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At 2008-07-23 12:36AM, "syang8" wrote:
> Is there any peal script available that I can quickly calculate a
> string " (3+5)*5/40 " or " 4*7-7*(4+5) " ? There are only the digits
> and +,-,*,/ and () available in the string. Thank you!

$str =~ m and $result = eval $1;

This does not check that your expression is "well formed" (e.g. $str="1+")

--
Glenn Jackman
Write a wise saying and your name will live forever. -- Anonymous

Posted by Jürgen Exner on July 23, 2008, 10:50 am
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>At 2008-07-23 12:36AM, "syang8" wrote:
>> Is there any peal script available that I can quickly calculate a
>> string " (3+5)*5/40 " or " 4*7-7*(4+5) " ? There are only the digits
>> and +,-,*,/ and () available in the string. Thank you!
>
> $str =~ m and $result = eval $1;
>
>This does not check that your expression is "well formed" (e.g. $str="1+")

Yes, it does:

        If there is a syntax error or runtime error, [...],
        an undefined value is returned by "eval", [...]

The code doesn't doesn't do any error handling, but that's a different
animal.

jue

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