variable not defined in a if statement

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Summary:

I am attempting to write a modular inverse function based on this c++ version in my TI-Nspire CX So far I have the following code, but am getting variable not defined in if statement.

variable not defined in a if statement

Pemby 10 May 2020 19:14

I am attempting to write a modular inverse function based on this c++ version

#include <iostream>
 using namespace std;

int mul_inv(int a, int b)
{
    int b0 = b, t, q;
    int x0 = 0, x1 = 1;
    if (b == 1) return 1;
    while (a > 1) {
        q = a / b;
        t = b, b = a % b, a = t;
        t = x0, x0 = x1 - q * x0, x1 = t;
    }
    if (x1 < 0) x1 += b0;
    return x1;
}

int main(void) {
    cout<<mul_inv(42, 2017)<<endl;
    return 0;
}

in my TI-Nspire CX So far I have the following code but am getting variable not defined in if statement.

Here is the code I have in my Nspire CX so far.

Define LibPub modinv(a,b)=
Func
 Local b0,t,q,x0,x1
 0→x0
 1→x1
 If b=1 Then
   Return 1
 EndIf
 While a>1
 q:=((a)/(b))
 t:=b
 b:=mod(a,b)
 a:=t
 t:=x0
 x0:=x1-q*x0
 x1:=t
 EndWhile
 If x1<0 Then
   x1:=x1+b0
 EndIf
 Return x1
 EndFunc

the inspire is throwing an error on this line.

 If x1<0 Then
   x1:=x1+b0
 EndIf

Not sure what I am doing wrong here! Any insight would be appreciated!

Re: variable not defined in a if statement

Xeda Elnara 16 May 2020 19:31

I don't have my nspire to test on, but it looks like you are creating a function, so maybe you need something like this at the top:

Local x0,x1,q,t

Also, what is b0? Do you mean to use b? You don't seem to have it declared anywhere. I hope you figure it out; I always like a good mod inverse :)

EDIT: Wow, I have no idea how I missed that you already had that Local definition at the top, sorry!

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Last edited on 16 May 2020 19:33 by Xeda Elnara Show more