1. Name this program math.c – This program takes three command line arguments. T

Question

1. Name this program math.c – This program takes three command line arguments. The first is an integer. The second is an operator, one of +– * / %. The third is a second integer. It does the integer math requested and prints the result. You can assume the input will always be legal. Several sample executions are shown below.

./a.out 2 + 3 ./a.out 100 – 99 ./a.out 3 * 30 ./a.out 15 / 4 ./a.out 20 % 6

Note, since * is a wildcard character, you need to handle multiplication via ./a.out 3 * 30 If you do this, then your third command line argument is simply the * character itself.

Explanation / Answer

#include <stdio.h>
#include <stdlib.h>
#include "calc.h"

#ifndef TEST_1xx
int main(int argc, char* args[]){
int operand1, operand2, answer;
char operator;

if(argc != 4) {
    printUsageMessage();
    return EXIT_FAILURE;
}

/* The expression "args[1][0]" means "the 0th (first) character
   * of the second command line argument (the character array at args[1])".
   */
operator = lookupOperator(args[1][0]);
if(operator == '?') {
    printUsageMessage();
    return EXIT_FAILURE;
}

/* This program assumes that args[2] and args[3] are strings that contain
   * numeric characters, e.g. "45", "235". Since for the homework we're only
   * concerned about the correct behavior of the non-main() methods, this is fine.
   */
operand1 = atoi(args[2]);
operand2 = atoi(args[3]);
answer = evaluateExpression(operator, operand1, operand2);
printf("%d %c %d = %d ", operand1, operator, operand2, answer);
}

#endif

int printUsageMessage() {
printf("Usage: ./calc [a|A|s|S|m|M|d|D] integer1 integer2 ");
printf(" Example Input: ./calc a 2 3 ");
printf(" Example Output: 5 ");
printf(" Exiting. ");
}

/*
* lookupOperator()
*
*   Input            Output
*   ~~~~~~~~~~       ~~~~~~
*   'a' or 'A'       '+'
*   's' or 'S'       '-'
*   'm' or 'M'       '*'
*   'd' or 'D'       '/'
*   anything else    '?'
*/
// PUT CODE FOR lookupOperator() HERE
char lookupOperator(char input){
   return '?'
}

/*
* The evaluateExpression function
*
* Input:
*     1. an operator (e.g. '+', '-', '*', '/')
*     2. an integer (the first operand)
*     3. an inteter (the second operand)
*
* Output:
*    The value of the expression (e.g. 8 if the inputs are '+', 3, 5)
*
* If operator is invalid, calls the printUsageMessage() and exit(EXIT_FAILURE).
*/
// PUT CODE FOR evaluateExpression() HERE
int evaluateExpression(char a, int b, int c){
   return 1;
}

calc.h
// calc.h

// function declarations
char lookupOperator(char);
int evaluateExpression(char, int, int);
int printUsageMessage();

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