Expression evaluator in just 8 lines of code

Trond · Post by **Trond** » Thu Dec 07, 2006 4:23 pm

Procedure.l Eval(String.s)
  Protected Program.l, Result.l
  Program = RunProgram("cmd", "/c set /a " + String, "", #PB_Program_Open | #PB_Program_Read | #PB_Program_Hide)
  WaitProgram(Program)
  Result = Val(ReadProgramString(Program))
  CloseProgram(Program)
  ProcedureReturn Result
EndProcedure

Debug Eval("5+2*10")

AND51 · Post by **AND51** » Thu Dec 07, 2006 4:33 pm

Just 7 lines

Code: Select all

Procedure.l Eval(String.s) 
  Protected Program = RunProgram("cmd", "/c set /a " + String, "", #PB_Program_Open | #PB_Program_Read | #PB_Program_Hide) 
  WaitProgram(Program) 
  Protected Result = Val(ReadProgramString(Program)) 
  CloseProgram(Program) 
  ProcedureReturn Result 
EndProcedure 

Debug Eval("5+2*10")

Nice idea, the example works.

Max · Post by **Max** » Thu Dec 07, 2006 4:34 pm

hard!

PB · Post by PB » Thu Dec 07, 2006 9:20 pm

Both versions don't work with floats (try 22/7) making them a bit useless.

Oh, and they don't work with Windows 9x/Me either, which may be an issue.

dracflamloc · Post by **dracflamloc** » Thu Dec 07, 2006 9:53 pm

I doubt this was really intended to be taken seriously...

AND51 · Post by **AND51** » Thu Dec 07, 2006 10:11 pm

I just copied the original code and I removed the first Protected-line.

Tested under XP, works. Don't forget to try command.com instead of cmd.exe if you do not have XP...

22/7 ? Not tested yet. I assume, that command/cmd cannot handle floats, just integers.

Trond · Post by **Trond** » Thu Dec 07, 2006 11:09 pm

Max wrote: hard!

... to think of?

PB wrote:Both versions don't work with floats (try 22/7) making them a bit useless.
Oh, and they don't work with Windows 9x/Me either, which may be an issue.

Not useless for integer expressions.

On the other hand, it supports hexadecimal and octal numbers.
But yes, I didn't think about the 9x problem. That's a real problem.

dracflamloc wrote:I doubt this was really intended to be taken seriously...

Yes, it's not exactly serious, but it actually can be used.

dracflamloc · Post by **dracflamloc** » Thu Dec 07, 2006 11:40 pm

Oh yes I know. Its kind of a neat hack. I didn't realize that you could do that with the set command.

va!n · Post by **va!n** » Fri Dec 08, 2006 11:05 am

codelines size compo?

just 4 lines... ok, it could fit in one line

Code: Select all

Procedure.l Eval(String.s)
  Protected Program = RunProgram("cmd", "/c set /a " + String, "", #PB_Program_Open | #PB_Program_Read | #PB_Program_Hide), Result = Val(ReadProgramString(Program))
  WaitProgram(Program) And CloseProgram(Program) : ProcedureReturn Result
EndProcedure

Debug Eval("5+2*10")

Konne · Post by **Konne** » Fri Dec 08, 2006 11:38 am

Doesn't work with unicode either.

Heathen · Post by **Heathen** » Fri Dec 08, 2006 9:23 pm

va!n wrote:codelines size compo?

just 4 lines... ok, it could fit in one line

Code: Select all

Procedure.l Eval(String.s)
  Protected Program = RunProgram("cmd", "/c set /a " + String, "", #PB_Program_Open | #PB_Program_Read | #PB_Program_Hide), Result = Val(ReadProgramString(Program))
  WaitProgram(Program) And CloseProgram(Program) : ProcedureReturn Result
EndProcedure

Debug Eval("5+2*10")

utopiomania · Post by **utopiomania** » Fri Dec 08, 2006 11:46 pm

Trond, I posted:

Expression Evaluator in just 45 lines of code

Then you had to post:

Expression Evaluator in just 8 lines of code

Only mine is as useful to yours as 45 is to .00008!

What a sorry hack, I mean, Integer math only? No functions or variables? I doubt you can be a Norwegian after all.

Trond · Post by **Trond** » Fri Dec 08, 2006 11:57 pm

Well, you can use variables.

utopiomania · Post by **utopiomania** » Sat Dec 09, 2006 12:14 am

Ohh, variables, well, rocket science then!

PB · Post by PB » Sat Dec 09, 2006 12:45 am

> Ohh, variables, well, rocket science then!

That is the funniest pic I've seen in ages! A definite keeper!