Control Flow

Logical Operators

Here are some logical operators you can use in expressions:

Expression	True If…
`expr1 == expr2`	`expr1` is equal to `expr2`
`expr1 != expr2`	`expr1` is not equal to `expr2`
`expr1 < expr2`	`expr1` is less than `expr2`
`expr1 <= expr2`	`expr1` is less than or equal to `expr2`
`expr1 > expr2`	`expr1` is greater than `expr2`
`expr1 >= expr2`	`expr1` is greater than or equal to `expr2`
`!expr`	`expr` is false (i.e., zero)
`expr1 && expr2`	`expr1` and `expr2` are true
`expr1 \|\| expr2`	`expr1` or `expr2` is true

false && expr2 will always evaluate to false, and true || expr2 will always evaluate to true, regardless of what expr2 evaluates to. This is called “short circuiting”: C evaluates the left-hand side of these expressions first and, if the truth value of that expression means that the other one doesn’t matter, it won’t evaluate the right-hand side at all.

Conditionals

Here is the syntax for if/else conditions:

if (condition) {
  // code to execute if condition is true
} else if (another_condition) {
  // code to execute if condition is false but another_condition is true
} else {
  // code to execute otherwise
}

The else if and else parts are optional.

Switch/Case

A switch statement can be a succinct alternative to a cascade of if/elses when you are checking several possibilities for one expression.

switch (expression) {
  case constant1:
    // code to execute if expression equals constant1
    break;
  case constant2:
    // code to execute if expression equals constant2
    break;
  // ...
  default:
    // code to be executed if expression doesn't match any case
}

While Loop

while (condition) {
  // code to execute as long as condition is true
}

For Loop

for (initialization; condition; increment) {
  // code to execute for each iteration
}

Roughly speaking, this for loop behaves the same way as this while equivalent:

initialization;
while (condition) {
  // code to execute for each iteration
  increment;
}

`break` and `continue`

To exit a loop early, use a break; statement. A break statement jumps out of the innermost enclosing loop or switch statement. If the break statement is inside nested contexts, then it exits only the most immediately enclosing one.

To skip the rest of a single iteration of a loop, but not cancel the loop entirely, use continue.

CS 3410