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Need to evaluate simple arithmetic expression

 
 
mstorkamp@yahoo.com
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      11-20-2007
I need to evaluate simple arithmetic expressions.

I wrote a quick and dirty program that allows me to enter dimensions
off of a drawing, and based on global or local tolerances calculate an
upper and lower limit to put in an inspection worksheet.

When it asks for a dimension I would like to be able to type in
something like: '(12.5+10)/2' or '150-3.45'

What I'm looking for is a function along the lines of 'double
evaluate_expression(char *)' that would solve simple 4-function
arithmetic with parenthesis.

(and I don't want to have to write it myself)

I've had no luck googling for such a function. Does anybody have one
or have a link to download one? Thanks.
 
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jameskuyper@verizon.net
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      11-20-2007


(E-Mail Removed) wrote:
> I need to evaluate simple arithmetic expressions.
>
> I wrote a quick and dirty program that allows me to enter dimensions
> off of a drawing, and based on global or local tolerances calculate an
> upper and lower limit to put in an inspection worksheet.
>
> When it asks for a dimension I would like to be able to type in
> something like: '(12.5+10)/2' or '150-3.45'
>
> What I'm looking for is a function along the lines of 'double
> evaluate_expression(char *)' that would solve simple 4-function
> arithmetic with parenthesis.
>
> (and I don't want to have to write it myself)
>
> I've had no luck googling for such a function. Does anybody have one
> or have a link to download one? Thanks.


Do you really need a function? Would a stand-alone program be
acceptable? I would ordinarily use a spreadsheet program for that kind
of stuff. If you're using a Unix-like system, there's also a program
called bc that makes it easy to evaluate simple expressions - but
definitely read the man page before trying to use it, it's not very
user-friendly.
 
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Richard Heathfield
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      11-20-2007
http://www.velocityreviews.com/forums/(E-Mail Removed) said:

> I need to evaluate simple arithmetic expressions.


This might do the trick:

http://webscripts.softpedia.com/scri...l-C-26706.html

> I've had no luck googling for such a function. Does anybody have one
> or have a link to download one? Thanks.


I got the above hit with the search terms

eval simple c

(It was the third hit.)

It probably originates from http://www.snippets.org/ which has got a ton of
useful stuff. Well worth a look.

--
Richard Heathfield <http://www.cpax.org.uk>
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999
 
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mstorkamp@yahoo.com
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      11-20-2007
On Nov 20, 10:19 am, Richard Heathfield <(E-Mail Removed)> wrote:
> (E-Mail Removed) said:
>
> > I need to evaluate simple arithmetic expressions.

>
> This might do the trick:
>
> http://webscripts.softpedia.com/scri...l-C-26706.html
>
> > I've had no luck googling for such a function. Does anybody have one
> > or have a link to download one? Thanks.

>
> I got the above hit with the search terms
>
> eval simple c
>
> (It was the third hit.)
>
> It probably originates fromhttp://www.snippets.org/which has got a ton of
> useful stuff. Well worth a look.
>


Thanks for the links, that's just what I was looking for. (and I tried
every permutation of arithmetic, function, evaluation, etc I could
think of, honestly
 
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Ben Pfaff
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      11-20-2007
(E-Mail Removed) writes:

> I need to evaluate simple arithmetic expressions.


libmatheval
http://www.gnu.org/software/libmatheval/
--
"...what folly I commit, I dedicate to you."
--William Shakespeare, _Troilus and Cressida_
 
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hsmit.home@gmail.com
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Posts: n/a
 
      11-20-2007
On Nov 20, 4:49 pm, (E-Mail Removed) wrote:
> I need to evaluate simple arithmetic expressions.
>
> I wrote a quick and dirty program that allows me to enter dimensions
> off of a drawing, and based on global or local tolerances calculate an
> upper and lower limit to put in an inspection worksheet.
>
> When it asks for a dimension I would like to be able to type in
> something like: '(12.5+10)/2' or '150-3.45'
>
> What I'm looking for is a function along the lines of 'double
> evaluate_expression(char *)' that would solve simple 4-function
> arithmetic with parenthesis.
>
> (and I don't want to have to write it myself)
>
> I've had no luck googling for such a function. Does anybody have one
> or have a link to download one? Thanks.


Another piece of code that does what you want, and is more C++
oriented is provided in the following link:

http://www.codeproject.com/cpp/rpnex...nevaluator.asp

It's very clean and concise code. Hat's off to the developer.

Hans Smit
 
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user923005
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Posts: n/a
 
      11-20-2007
On Nov 20, 7:49 am, (E-Mail Removed) wrote:
> I need to evaluate simple arithmetic expressions.
>
> I wrote a quick and dirty program that allows me to enter dimensions
> off of a drawing, and based on global or local tolerances calculate an
> upper and lower limit to put in an inspection worksheet.
>
> When it asks for a dimension I would like to be able to type in
> something like: '(12.5+10)/2' or '150-3.45'
>
> What I'm looking for is a function along the lines of 'double
> evaluate_expression(char *)' that would solve simple 4-function
> arithmetic with parenthesis.
>
> (and I don't want to have to write it myself)
>
> I've had no luck googling for such a function. Does anybody have one
> or have a link to download one? Thanks.


It's a FAQ:

18.14: I need code to parse and evaluate expressions.

A: Two available packages are "defunc," posted to
comp.sources.misc
in December, 1993 (V41 i32,33), to alt.sources in January,
1994,
and available from sunsite.unc.edu in
pub/packages/development/libraries/defunc-1.3.tar.Z, and
"parse," at lamont.ldgo.columbia.edu. Other options include
the
S-Lang interpreter, available via anonymous ftp from
amy.tch.harvard.edu in pub/slang, and the shareware Cmm ("C-
minus-minus" or "C minus the hard stuff"). See also questions
18.16 and 20.6.

There is also some parsing/evaluation code in _Software
Solutions in C_ (chapter 12, pp. 235-55).

Those solutions may no longer be available so the other suggestions
elsethread may be helpful.

You could always use yacc or bison or the gold parser to make your own
grammar. Might be a fun exercise.
 
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