3. A goal is not always meant to be reached, it often serves simply as something to aim at

Write a program that performs simple operations.

• You are allowed to use the standard library
• Usage: calc num1 operator num2
• You can assume num1 and num2 are integers, so use the atoi function to convert them from the string input to int
• operator is one of the following:
  • +: addition
  • -: subtraction
  • *: multiplication
  • /: division
  • %: modulo
• The program prints the result of the operation, followed by a new line
• You can assume that the result of all operations can be stored in an int
• if the number of arguments is wrong, print Error, followed by a new line, and exit with the status 98
• if the operator is none of the above, print Error, followed by a new line, and exit with the status 99
• if the user tries to divide (/ or %) by 0, print Error, followed by a new line, and exit with the status 100

This task requires that you create four different files.

3-calc.h

This file should contain all the function prototypes and data structures used by the program. You can use this structure:

/**
 * struct op - Struct op
 *
 * @op: The operator
 * @f: The function associated
 */
typedef struct op
{
    char *op;
    int (*f)(int a, int b);
} op_t;

3-op_functions.c

This file should contain the 5 following functions (not more):

• op_add: returns the sum of a and b. Prototype: int op_add(int a, int b);
• op_sub: returns the difference of a and b. Prototype: int op_sub(int a, int b);
• op_mul: returns the product of a and b. Prototype: int op_mul(int a, int b);
• op_div: returns the result of the division of a by b. Prototype: int op_div(int a, int b);
• op_mod: returns the remainder of the division of a by b. Prototype: int op_mod(int a, int b);

3-get_op_func.c

This file should contain the function that selects the correct function to perform the operation asked by the user. You’re not allowed to declare any other function.

• Prototype: int (*get_op_func(char *s))(int, int);
• where s is the operator passed as argument to the program
• This function returns a pointer to the function that corresponds to the operator given as a parameter. Example: get_op_func("+") should return a pointer to the function op_add
• You are not allowed to use switch statements
• You are not allowed to use for or do ... while loops
• You are not allowed to use goto
• You are not allowed to use else
• You are not allowed to use more than one if statement in your code
• You are not allowed to use more than one while loop in your code
• If s does not match any of the 5 expected operators (+, -, *, /, %), return NULL
• You are only allowed to declare these two variables in this function:

    op_t ops[] = {
        {"+", op_add},
        {"-", op_sub},
        {"*", op_mul},
        {"/", op_div},
        {"%", op_mod},
        {NULL, NULL}
    };
    int I;

3-main.c

This file should contain your main function only.

• You are not allowed to code any other function than main in this file
• You are not allowed to directly call op_add, op_sub, op_mul, op_div or op_mod from the main function
• You have to use atoi to convert arguments to int
• You are not allowed to use any kind of loop
• You are allowed to use a maximum of 3 if statements

Compilation and examples

julien@ubuntu:~/0x0e. Function pointers$ gcc -Wall -pedantic -Werror -Wextra -std=gnu89 3-main.c 3-op_functions.c 3-get_op_func.c -o calc
julien@ubuntu:~/0x0e. Function pointers$ ./calc 1 + 1
2
julien@ubuntu:~/0x0e. Function pointers$ ./calc 97 + 1
98
julien@ubuntu:~/0x0e. Function pointers$ ./calc 1024 / 10
102
julien@ubuntu:~/0x0e. Function pointers$ ./calc 1024 '*' 98
100352
julien@ubuntu:~/0x0e. Function pointers$ ./calc 1024 '\*' 98
Error
julien@ubuntu:~/0x0e. Function pointers$ ./calc 1024 - 98
926
julien@ubuntu:~/0x0e. Function pointers$ ./calc 1024 '%' 98
44
julien@ubuntu:~/0x0e. Function pointers$ 

Repo:

• GitHub repository: holbertonschool-low_level_programming
• Directory: 0x0F-function_pointers
• File: 3-main.c, 3-op_functions.c, 3-get_op_func.c, 3-calc.h