Let a user write an expression as a string and return a value

[Federico Caselli]

I'm using visual basic.net, I need to take in input a string containing an
expression and return the value, example:

"14=14" must return true
"14+14" must return 28
"8<4" must return false

[Morten Wennevik]

Re: Let a user write an expression as a string and return a value

Hi Federico,

I believe you will have to do this manually the hard way by splitting
operators and numbers by presedence and possibly recursively.

On Fri, 21 Jan 2005 00:43:04 -0800, Federico Caselli
<FedericoCasell i@discussions.m icrosoft.com> wrote:
[color=blue]
> I'm using visual basic.net, I need to take in input a string containing
> an
> expression and return the value, example:
>
> "14=14" must return true
> "14+14" must return 28
> "8<4" must return false[/color]



--
Happy Coding!
Morten Wennevik [C# MVP]

[Steven Spits]

Re: Let a user write an expression as a string and return a value

"Federico Caselli" wrote:
[color=blue]
> I'm using visual basic.net, I need to take in input a string containing an
> expression and return the value, example:[/color]

This is possible by generating code, compile it and execute, all at runtime!

I've done it, works like a charm! This article got me started:

http://www.odetocode.com/Code/80.aspx

Steven

- - -

[Federico Caselli]

Re: Let a user write an expression as a string and return a value

Thank you. The class Evaluator is really what I need. Just one thing: I need
to evaluate a boolean expression, like "84 < 70" or "7 >=8". So I tried to
add the following method to the class Evaluator
-------------------------------------------------------------------------------------
public static bool EvalToBoolean(s tring statement)
{
string s = EvalToString(st atement);
return bool.Parse(s.To String());

-------------------------------------------------------------------------------------

When I try to use the method

blnRes = Evaluator.EvalT oBoolean("7<8")

I get an exception.

Is there a way to make it work?

Thank you




"Steven Spits" wrote:
[color=blue]
> "Federico Caselli" wrote:
>[color=green]
> > I'm using visual basic.net, I need to take in input a string containing an
> > expression and return the value, example:[/color]
>
> This is possible by generating code, compile it and execute, all at runtime!
>
> I've done it, works like a charm! This article got me started:
>
> http://www.odetocode.com/Code/80.aspx
>
> Steven
>
> - - -
>
>
>[/color]