conditionals.md

#Conditionals In C

if and else

The syntax for conditionals in C is very common; many languages were influenced by C.

if (1) {
  printf("I will always print.");
}
else {
  printf("I will never print.");
}

If the expression within your conditional is only one line, then you may omit the curly-braces:

if (1)
  printf("I will always print.");
else
  printf("I will never print.");
  printf("I will ACTUALLY always print.");

Remember that in C, we use 0 as 'false' and any number that is not 0 as 'true'.

The ? ternary operator provides an even more short-hand way to write this:

(1) ? printf("I will always print.") : printf("I will never print.");

You may chain multiple if and else expressions together:

int current_temperature = 90;

if (current_temperature == -10)
  printf("Brrrrrr!\n");
else if ((current_temperature > 50) && (current_temperature < 70))
  printf("Mmmm - just right.\n");
else
  printf("Getting toasty!\n");

However if you have many different cases to test then you may prefer a switch statement.

##switch A switch statement tests an expression against a series of constant integer values. We could write a similar program to above as follows:

int current_temperature = 90;

switch (current_temperature) {
  case -10: case -9: case -8: case -7: case -6: case -5: case -4: case -3: case
  -2: case -1: case 0:
    printf("Brrrrrr!\n");
    break;
  case 50:
  case 60:
  case 70:
    printf("Mmmm - just right.\n");
    break;
  case 90:
    printf("Getting toasty!\n");
    break;
  default:
    printf("It's a fine day.\n");
    break;
}

printf("Outside the switch~\n");

If the current_temperature is equal to the value following any case statement, then the code beneath that case will execute. A break causes an immediate exit from the switch, and would jump to the line with printf("Outside the switch~\n");`. The above code would output:

Getting toasty! Outside the switch~

Reference: "The C Programming Language" p. 51-52