CODEWITHSUNDEEP
c
hannah
hannah

Reputation: 909

Newbie: convert input from getch() into an int

// get user's input
int ch = getch();

switch (ch)
    {
        //input a number
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
        case '8':
        case '9':
            {

            int i = atoi(ch);

            g.board[g.y][g.x] = i;

            }
}

In the code I was given to add on to, ch was declared as an int. However, the function getch saves input as a string, correct? How can I convert the string ch into an int so I can work with it? I tried to use the atoi() function, but I keep getting these error messages.

sudoku.c: In function 'main':
sudoku.c:247:17: error: passing argument 1 of 'atoi' makes pointer from integer without a cast [-Werror]
/usr/include/stdlib.h:148:12: note: expected 'const char *' but argument is of type 'int'
sudoku.c:252:17: error: expected ';' before 'g'
sudoku.c:244:21: error: unused variable 'y' [-Werror=unused-variable]
cc1: all warnings being treated as errors

Upvotes: 2

Views: 11767

Answers (5)

Alvin Sudarta
Alvin Sudarta

Reputation: 11

just subtract with '0' and it will automatically become an integer. The x is your variable

 int x;
 x=getch()-'0';

Upvotes: 1

TaeL
TaeL

Reputation: 1066

        int i = atoi(ch);

replace this code below

int i = atoi((const char *)&ch);

you can find this with manual (Linux)

# man atoi

prototype is 

#include <stdlib.h>

int atoi(const char *nptr);

Upvotes: -2

user7116
user7116

Reputation: 64098

atoi expects a C-string (a \0/nul terminated string). In your example you are passing it a single character.

Instead, utilize the benefits of the ASCII table layout:

/* Assuming (ch >= '0' && ch <= '9') */
int value = ch - '0';
/* Borrows from the fact that the characters '0' through '9' are laid
   out sequentially in the ASCII table. Simple subtraction allows you to 
   glean their number value.
 */

Upvotes: 1

JaredPar
JaredPar

Reputation: 755209

Try the following

int i = (int)((char)ch - '0');

The numbers 0-9 are laid out in ascending order in terms of character codes. Hence subtracting '0' from the char value will produce an offset that is equal to the actual number in question

Upvotes: 3

cnicutar
cnicutar

Reputation: 182674

the function getch saves input as a string, correct?

No, getch reads a character and returns an int (you did correctly define ch as int). The easiest way to convert it to a real integer is to subtract '0'. So after validating getch, you can replace most of your code with:

if (isdigit(ch))
    g.board[g.y][g.x] = ch - '0';

Upvotes: 7

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