How to evaluate arithmetic expressions in Skill

[micpro]

I'm looking for a solution to evaluate mathematical arithmetic expressions in Skill.

Due to the mix of infix and postfix notations in Skill, evalstring doesn't always work. For example, "(3)*(4)" is a valid arithmetical expression, but evalstring can't evaluate it. Same for "2*(cos(17))".

Or consider these examples:

> evalstring("(4 +5)*3")
> 27
> evalstring("(4 -5)*3")
*Error* eval: not a function - 4

> evalstring("+4*3")

+4*3
^
SYNTAX ERROR found at line 1 column 2 of file *string*
*Error* lineread/read: syntax error encountered in input
> evalstring("4*(-5)")
-20
> evalstring("4*(+5)")

4*(+5)
^
SYNTAX ERROR found at line 1 column 5 of file *string*
*Error* lineread/read: syntax error encountered in input

and so on ...
Any ideas?

 

[vijayR15]

Hai micpro,

Here is a solution for u..

case 1:-
evalstring("(4 -5)*3")

u can execute like this.. It will work

evalstring("plus(4 -5)*3")

Case 2:-
evalstring("+4*3")

This will work

evalstring("minus(-4)*3")

Case 3:-

evalstring("4*(+5)")

use like this

evalstring("4*minus(-5)")

Hope u will be happy:razz:

 

[micpro]

Hi vijay,

thank you for your response. I should have mentioned a detail in my post: the string to be evaluated is coming from an external program and my program does not know it in advance. My program is evaluating it.
Assume the string is inside a variable t_input. If my program simply calls

result=evalstring(t_input)

then it will fail for the cases that I mentioned in my post. How can I calculate the result of an arithmetic expression given inside a string-valued variable, the content of which I don't know when writing the software?

Regards,
Michael

 

[vijayR15]

Then it is too easy micpro compare to the past. u will not know only the value of a variable..,, but u know whether its string or numerical.. If u are sure that every input will be string then


mention like this


but dont forget it should be mentioned only for sting.. For numerical value dont use evalstring

case 1:-

(evalstring("4") + evalstring("-5")) * evalstring("3")

case 2:-

(evalstring("4") * evalstring("3"))

case 3:-

(evalstring("-4") * evalstring("3"))

use evalstring separately u can achieve what u want..

optional case:-
if u are not sure that its a numerical variable or string variable then just

store it in a string variable if its a numerical variable or string variable and then pass it to above evalstring statement..