General Purpose Eval

[JosephE]

Thanks Eros, I wasn't too familiar with the Format$() function.

Why does this return 1? Eval_Math() returns 0 correctly. In my implementation, I'm blind as to what we're evaluating. So how do I tell which evaluator is right?

Your code checks to see if the number from string and the string are the same thing. If they are, it assumes it's a number. But in this case, it's different (for some reason unknown to me), so it's throwing it off.

Uses "Console"
Uses "Eval"

PrintL Evaluate("1 = 0")

WaitKey
 
Function Evaluate(strng As String) As String
 Return Eval_String(strng)
End Function

[ErosOlmi]

Mainly because all logical comparisons are numerical expressions and not string expressions.

"1 = 0"
is a numerical expression and has no meaning for a string expression.

STR$(1 = 0)
is a string expression and here 1 = 0 will correctly be evaluated as 0 because STR$() expect a numerical expression.

Of course I can improve Eval module but I would go far behind its purpose and creating a full interpreter inside an interpreter would require too much time.
In any case if necessary I can think about it.

[JosephE]

Don't worry about it for now, I'll survive without it for the time being. Although I probably will need this when development gets further along.

[JosephE]

This here produces the correct result on string, number, and comparison results:

I'm happy.

Uses "Console"
Uses "Eval"

PrintL Evaluate("Str$(1 = 1)")
PrintL Evaluate("1=0")
PrintL Evaluate("""1""")
PrintL Evaluate("Format$(Len(Parse$(""hello, world"","" "", 1)))")
PrintL Evaluate("Parse$(""hello, world"","" "", 1)))")
PrintL Evaluate("15>5")
PrintL Evaluate("15+sin(15)/(10^2)")

WaitKey
 
Function Evaluate(strng As String) As String
 Dim expression, original As String
 expression = ("Str$(" & strng & ") & """"")
 expression = Eval_String(expression)
 original = Eval_String(strng)
 If Format$(Val(Trim$(original))) <> Trim$(original) Then Return original
 Return expression
End Function

[peralta_mike]

Hello,

Is there any way that EVAL can be extended to work with any of the thinbasic functions?

Or can I create functions that EVAL will work with (in addition to the ones already there)?

- Mike Peralta

[ErosOlmi]

No, I'm sorry.

Eval is just a small interpreter inside an interpreter.

Maybe in future I will be able to extend in such a way script functions can be used inside Eval but at the moment not.