Is 1 and 0 always have to be true or false in C?-CodePudding

Recently I found some code that is very interesting to me, but I can't properly understand it, so can someone please explain it to me?

It's Conway's Game of Life. I think this row can be like a question and 1 meaning true and 0 meaning false; is that correct? But why is there no bool?

void iterGen(int WIDTH, int HEIGHT, char curMap[WIDTH][HEIGHT])
{
    int i, j;
    char tempMap[WIDTH][HEIGHT];

    for (i = 0; i < WIDTH; i  )
    {
        for (j = 0; j < HEIGHT; j  )
        {
            int neighbors = 0;
            neighbors  = curMap[i 1][j 1] == '*' ? 1 : 0;
            neighbors  = curMap[i 1][j] == '*' ? 1 : 0;
            neighbors  = curMap[i 1][j-1] == '*' ? 1 : 0;
            neighbors  = curMap[i][j 1] == '*' ? 1 : 0;
            neighbors  = curMap[i][j-1] == '*' ? 1 : 0;
            neighbors  = curMap[i-1][j 1] == '*' ? 1 : 0;
            neighbors  = curMap[i-1][j] == '*' ? 1 : 0;
            neighbors  = curMap[i-1][j-1] == '*' ? 1 : 0;

            if (curMap[i][j] == ' ')
            {
                tempMap[i][j] = neighbors == 3 ? '*' : ' ';
            }
            else if (curMap[i][j] == '*')
            {
                tempMap[i][j] = neighbors < 2 || neighbors > 3 ? ' ' : '*';
            }
        }
    }

    for (i = 0; i < WIDTH; i  )
    {
        for (j = 0; j < HEIGHT; j  )
        {
            curMap[i][j] = tempMap[i][j];
        }
    }
}

CodePudding user response：

First, a couple of comments.

neighbors  = curMap[...][...] == '*' ? 1 : 0

is a redundant way of writing

neighbors  = curMap[...][...] == '*'

since the comparison operators already return 1 or 0.

But neither are as clear as

if ( curMap[...][...] == '*' )   neighbors;

1 meaning true and 0 meaning false; is that correct? But why is there no bool?

Not quite. 0 is false (including 0 as a pointer, NULL). All other values are true.

Now, on to the question.

But why there is no bool?

But there is: _Bool.

stdbool.h provides bool as an alias, as well as the macros true and false.

#include <stdbool.h>
#include <stdio.h>

bool flag = true;

if ( flag )
   printf( "True\n" );
else
   printf( "False\n" );

Demo on Compiler Explorer

Note that none of the variables in the snippet you posted are booleans, so I have no idea why that code was included in your question.

CodePudding user response：

Just like in most other languages, in C any value that is not 0 can be considered as true.

if ( 20 ) {
    // true
}
if ( -1 ) {
    // true
}

if ( 'c' ) {
    // true
}

if ( "string" ) {
    // true
}

if ( 0 ) {
    // false
}

if ( '\0' ) { // null terminator, a char with a value of 0
    // false
}

if ( NULL ) { // value of a null pointer constant
    // false
}

Bool is just a way to make code more readable.