Ruby mathematical expression parser

Rails
1

Hi,

Has anyone come across a Ruby mathematical expression parser, capable
of parsing out token, replacing them with values then executing the
mathematical formula? Nothing too heavy, A * (44/12) * … etc. where
A is can be replaced with a value.

In Java there are serveral, like JEP, but I’d prefer it we could get a
Ruby one now we have moved over to Rails, otherwise we will have to
have some sort of Java calculation web service which would be quite
faffy.

Thanks

Sean

2

Sean B. schrieb:

Hi,

Has anyone come across a Ruby mathematical expression parser, capable
of parsing out token, replacing them with values then executing the
mathematical formula? Nothing too heavy, A * (44/12) * … etc. where
A is can be replaced with a value.

Mmh, I’ve looking similar. Whats about

formular.gsub!(/A/,“0.2”)

result = eval(formular)

?

g,

3

On 6/6/06, Sean B. [email protected] wrote:

Has anyone come across a Ruby mathematical expression parser, capable
of parsing out token, replacing them with values then executing the
mathematical formula? Nothing too heavy, A * (44/12) * … etc. where
A is can be replaced with a value.

In Java there are serveral, like JEP, but I’d prefer it we could get a
Ruby one now we have moved over to Rails, otherwise we will have to
have some sort of Java calculation web service which would be quite
faffy.

I don’t know of one exactly, but what if you stripped out everything
but 0-9, ., *, /, (, and ), then passed it to a Ruby eval method? Are
there any safety concerns I’m neglecting?

Thanks

Sean

Sincerely,

Tom L.
http://AllTom.com/
http://GadgetLife.org/

4

Sean B. wrote:

Hi,

Has anyone come across a Ruby mathematical expression parser, capable
of parsing out token, replacing them with values then executing the
mathematical formula? Nothing too heavy, A * (44/12) * … etc. where
A is can be replaced with a value.

[stuff deleted]

Try this…

http://www.chipstips.com/?p=119

5

Sean B. wrote:

Hi,

Has anyone come across a Ruby mathematical expression parser, capable
of parsing out token, replacing them with values then executing the
mathematical formula? Nothing too heavy, A * (44/12) * … etc. where
A is can be replaced with a value.

Here’s how I do it:

– MarkusQ

6

Sean B. wrote:

Hi,

Has anyone come across a Ruby mathematical expression parser, capable
of parsing out token, replacing them with values then executing the
mathematical formula? Nothing too heavy, A * (44/12) * … etc. where
A is can be replaced with a value.

In Java there are serveral, like JEP, but I’d prefer it we could get a
Ruby one now we have moved over to Rails, otherwise we will have to
have some sort of Java calculation web service which would be quite
faffy.

Thanks

Sean

Ridiculous. You won’t need a calculation Web service. Even if nothing
exists off the shelf in Ruby, it would be very easy to generate a parser
with Treetop.

Best,

Marnen Laibow-Koser
http://www.marnen.org
[email protected]