无限循环，无法获取值

Question

I've spent literally 3 hours trying to get this code to work, however whenever I try I end up in a loop and the console continuously loops. I've tried everything - I've created a function that returns just i and reassigning values but it doesn't seem to work.

For some reason whenever I try use logic operators it doesn't want to work on me. The values of mes->hand[x] is something like "2D,4D,3C,5C,6H,7H" and so on whilst the suit is either "H", "C" , "D", "S" in reference to cards.

int newtrick_value(struct Message *mes, int suit) {
    int len = strlen(mes->hand);
    int x = 0, i = 50, y = 0;
    while (i < 63) {
        while(x < len) {
            if (((mes->hand[x] == i || mes->hand[x] == y) && mes->hand[x+1] == suit)){
                if(i>= 58){
                    return y;
                }   
                return i;
            }
            x++;
            continue;
        }
        if(i >= 57) {
            y = determine_letter(i);        
        }
        i ++;
        x = 0;
        continue;
    }
    return 0;
}

Answer 1

I have the following observations:

1. Your continue statements are redundant. You are already at the bottom of the loops. (No harm though.)

2. Your numbers 50 etc all refer to ASCII characters. Add comments about this.

3. the only error I can find is in:

    if(i >= 57) { y = determine_letter(i); } 

This should be if (i>=58) as 57 ASCII is 9 . Possibly determine_letter gets confused when receiving 57 (that function apparently maps cards higher than 9 onto your card encoding scheme, which you did not provide completely). As a result, the function can return an invalid value in return y; , which the calling function doesn't understand and which causes your console to loop.

Also this statement should be placed before while (x < len) , so you first map the character and then compare it and at the end of the loop increment i for the next character (card value) to compare.

Applying these observations gives:

int newtrick_value(struct Message *mes, int suit) {
    int len = strlen(mes->hand);
    int x = 0, i = 50, y = 0;
    while (i < 63) {
        if (i >= 58) {
            y = determine_letter(i);        
        }
        while (x < len) {
            if (((mes->hand[x] == i || mes->hand[x] == y) && mes->hand[x+1] == suit)){
                if (i >= 58) {
                    return y;
                }   
                return i;
            }
            x++;
        }
        i++;
        x = 0;
    }
    return 0;
}

Without all details of caller, sub-functions and card encoding scheme I cannot give more suggestions. I hope this helps.

Note: thinking about the functionality, the function just returns the value of the first card of the given suit. This means that the outer loop to compare the card value seems pretty useless: first find the first suit, then get its value is more efficient:

int newtrick_value(struct Message *mes, int suit) {
    int len = strlen(mes->hand);
    int x = 0;

    while (x < len) {
        if (mes->hand[x] == suit)){
            return(mes->hand[x-1]);
        }
        x++;
    }
    return 0;
}

Answer 2

As a MWE, this prints "calling determine letter" out to the console 6 times:

#include <stdio.h>
#include <string.h>

int newtrick_value(char* hand, int suit) {
    int len = strlen(hand);
    int x = 0, i = 50, y = 0;

    while (i < 63) 
    {
        x = 0;
        while(x < len) 
        {
            printf("i%d, y%d, suit %d, hand[x] %d, hand[x+1] %d\n", i, y, suit, hand[x], hand[x+1]);
            if (((hand[x] == i || hand[x] == y) && hand[x+1] == suit))
            {
                if(i>= 58)
                {
                    return y;
                }   
                return i;
            }
            x++;
        }
        if(i >= 57) 
        {
            printf("Calling determine letter\n");
            //y = determine_letter(i);        
        }

        i++;
    }
    return 0;
}

int main(void) 
{
    newtrick_value("2H,3H", (int)"H");
    return 0;
}

As far as I can tell, I didn't change any of the logic (just some of the formatting). It shouldn't be giving this behaviour, as the suit and value should match.

Oddly, the prints gave the following:

i50, y0, suit 134514349, hand[x] 50, hand[x+1] 72
i50, y0, suit 134514349, hand[x] 72, hand[x+1] 44
i50, y0, suit 134514349, hand[x] 44, hand[x+1] 51
i50, y0, suit 134514349, hand[x] 51, hand[x+1] 72
i50, y0, suit 134514349, hand[x] 72, hand[x+1] 0
i51, y0, suit 134514349, hand[x] 50, hand[x+1] 72
i51, y0, suit 134514349, hand[x] 72, hand[x+1] 44
i51, y0, suit 134514349, hand[x] 44, hand[x+1] 51
i51, y0, suit 134514349, hand[x] 51, hand[x+1] 72
i51, y0, suit 134514349, hand[x] 72, hand[x+1] 0
i52, y0, suit 134514349, hand[x] 50, hand[x+1] 72
i52, y0, suit 134514349, hand[x] 72, hand[x+1] 44
i52, y0, suit 134514349, hand[x] 44, hand[x+1] 51
i52, y0, suit 134514349, hand[x] 51, hand[x+1] 72
i52, y0, suit 134514349, hand[x] 72, hand[x+1] 0
i53, y0, suit 134514349, hand[x] 50, hand[x+1] 72
i53, y0, suit 134514349, hand[x] 72, hand[x+1] 44
i53, y0, suit 134514349, hand[x] 44, hand[x+1] 51
i53, y0, suit 134514349, hand[x] 51, hand[x+1] 72
i53, y0, suit 134514349, hand[x] 72, hand[x+1] 0
i54, y0, suit 134514349, hand[x] 50, hand[x+1] 72
i54, y0, suit 134514349, hand[x] 72, hand[x+1] 44
i54, y0, suit 134514349, hand[x] 44, hand[x+1] 51
i54, y0, suit 134514349, hand[x] 51, hand[x+1] 72
i54, y0, suit 134514349, hand[x] 72, hand[x+1] 0
i55, y0, suit 134514349, hand[x] 50, hand[x+1] 72
i55, y0, suit 134514349, hand[x] 72, hand[x+1] 44
i55, y0, suit 134514349, hand[x] 44, hand[x+1] 51
i55, y0, suit 134514349, hand[x] 51, hand[x+1] 72
i55, y0, suit 134514349, hand[x] 72, hand[x+1] 0
i56, y0, suit 134514349, hand[x] 50, hand[x+1] 72
i56, y0, suit 134514349, hand[x] 72, hand[x+1] 44
i56, y0, suit 134514349, hand[x] 44, hand[x+1] 51
i56, y0, suit 134514349, hand[x] 51, hand[x+1] 72
i56, y0, suit 134514349, hand[x] 72, hand[x+1] 0
i57, y0, suit 134514349, hand[x] 50, hand[x+1] 72
i57, y0, suit 134514349, hand[x] 72, hand[x+1] 44
i57, y0, suit 134514349, hand[x] 44, hand[x+1] 51
i57, y0, suit 134514349, hand[x] 51, hand[x+1] 72
i57, y0, suit 134514349, hand[x] 72, hand[x+1] 0
Calling determine letter
i58, y0, suit 134514349, hand[x] 50, hand[x+1] 72
i58, y0, suit 134514349, hand[x] 72, hand[x+1] 44
i58, y0, suit 134514349, hand[x] 44, hand[x+1] 51
i58, y0, suit 134514349, hand[x] 51, hand[x+1] 72
i58, y0, suit 134514349, hand[x] 72, hand[x+1] 0
Calling determine letter
i59, y0, suit 134514349, hand[x] 50, hand[x+1] 72
i59, y0, suit 134514349, hand[x] 72, hand[x+1] 44
i59, y0, suit 134514349, hand[x] 44, hand[x+1] 51
i59, y0, suit 134514349, hand[x] 51, hand[x+1] 72
i59, y0, suit 134514349, hand[x] 72, hand[x+1] 0
Calling determine letter
i60, y0, suit 134514349, hand[x] 50, hand[x+1] 72
i60, y0, suit 134514349, hand[x] 72, hand[x+1] 44
i60, y0, suit 134514349, hand[x] 44, hand[x+1] 51
i60, y0, suit 134514349, hand[x] 51, hand[x+1] 72
i60, y0, suit 134514349, hand[x] 72, hand[x+1] 0
Calling determine letter
i61, y0, suit 134514349, hand[x] 50, hand[x+1] 72
i61, y0, suit 134514349, hand[x] 72, hand[x+1] 44
i61, y0, suit 134514349, hand[x] 44, hand[x+1] 51
i61, y0, suit 134514349, hand[x] 51, hand[x+1] 72
i61, y0, suit 134514349, hand[x] 72, hand[x+1] 0
Calling determine letter
i62, y0, suit 134514349, hand[x] 50, hand[x+1] 72
i62, y0, suit 134514349, hand[x] 72, hand[x+1] 44
i62, y0, suit 134514349, hand[x] 44, hand[x+1] 51
i62, y0, suit 134514349, hand[x] 51, hand[x+1] 72
i62, y0, suit 134514349, hand[x] 72, hand[x+1] 0
Calling determine letter

So the suit value that's given by converting "H" to an integer seems particularly screwy.

I've made an assumption about how you've represented mes->hand in your structure, but hopefully this still holds. One thing I did notice though, is why are you passing in the suit as an int , not a char ? That seems like a much more logical thing to do.

As such, if you're getting into an infinite loop, my suspicion is that mes->hand may not be null-terminated, meaning that strlen(mes->hand) will return some unknown value, which would mean that while(x < len) may seem like it never terminates. Could you inspect mes->hand to ensure that it's a valid (and expected) string?