recursive functions with arrays as parameters

[nilushika]

I wrote a fuction in C with the prototype
'void raisePowerOf2(int array[],int pow);'

If someone want to find the value of 2^456 ,just have to invoke this function 456 as the value for pow and int array with 2 elements :1 & -1 as the argument for the array.(There I used -1 to denote the end of the array.)

But it seems that this function doesn't give the exact answer

And I tried this from java also,with the same implementation.It produced the answer precisely .

I tried for hours, but unable to detect reasons why this code blok in C doesn't work properly .
Can you please help me......


This is the code in c

#include<stdio.h>
void raisePowerOf2(int array[],int pow);
int main(){
    int a[2]={1,-1};
    raisePowerOf2(a,5);
 
    return 0;
}
 
 void raisePowerOf2(int array[],int pow){
    int i, qtnt=0;
    for(i=0;;i++){
    if(array[i]==-1)
    break;
        }
    const int len=i+1;
    int store[len+1];
 
    for(i=len-2;i>=0;i--){
    store[i+1]=(array[i]*2)%10+qtnt;
    qtnt=(array[i]*2)/10;
 
    }
    store[len]=-1;
 
    if(pow==1){
    for( i=0;i<len;i++)
        printf("%i",store[i]);
    }
 
    if(pow>1)
        raisePowerOf2(store,pow-1);
 
}

This is the code in java...

public class NewClass4 {
 
    void raisePowerOf2(int array[],int pow){
    final int len=array.length;
    int store[]=new int[len+1];
    int qtnt=0;
    for(int i=len-1;i>=0;i--){
    store[i+1]=(array[i]*2)%10+qtnt;
    qtnt=(array[i]*2)/10;
 
    }
store[0]=qtnt;
 
    if(pow==1){
    for(int i=0;i<len+1;i++)
        System.out.print(store[i]);
    }
 
    if(pow>1)
        raisePowerOf2(store,pow-1);
 
}
 
public static void main(String s[]){
 int a[]={1};
   new NewClass4().raisePowerOf2(a,5);
}    
 
 
}

[weaknessforcats]

Which C are you using?
This code:

const int len=i+1;
int store[len+1];
 

won't compile as either C or C++ with my compiler.

[nilushika]

i compiled this with c-free5.0.it compiles fine.i'd like to know what the error is,please.

[Nepomuk]

You never set store[0] to a value, so it takes a random value from memory. Just add

store[0]=0;

after line 5 and it should work.

[nilushika]

Thank you Nepomuk, that's the point!
I made line 25 as ' store[0]=qtnt;'I have forgot it.
Now it works ....
thnks for the all.

[nilushika]

Thank for all.....