Trapping owerflow errors in your own interpreter

[na_th_an]

Do a multiplication check in every multiplication done in the pow function.

M = M1 * M2 will overflow if M2 > 32767\M1

Generally:

A (operator) B will overflow if B > [max numer] (inv. operator) A.

Operator: +, Inv. operator: -
Operator: *, Inv. operator: /
Operator: pow, Inv. operator: nth root
...

[Z!re]

I can't test the number without making them VAL()?

(The numbers are stored as strings, ex: "289347")

The largest number you can pass to val is "1.xxxxxxxxxxxxxxD+308" witch is large, but still, if a stupid-user enters 4D+800 then it shouldn't crash, it should report the error, and my interpreter should remain in control.

So, I have 2 options:
1)

Code:

ON ERROR GOTO x
x:
IF ERR=6 THEN 'overflow
[...] 'dostuff
END IF

and 2)
Make my own ASM Math lib, that doesent crash on overflow, or find one already existing.

[na_th_an]

I can't test the number without making them VAL()?

(The numbers are stored as strings, ex: "289347")

The largest number you can pass to val is "1.xxxxxxxxxxxxxxD+308" witch is large, but still, if a stupid-user enters 4D+800 then it shouldn't crash, it should report the error, and my interpreter should remain in control.

you can parse the string, look for the D+ substring, look the number behind, and make sure that it is <800.