Assignments | Sugar

An assignment replaces the value stored in a mutable variable:

score = 10;

The single equals sign means “store the value on the right in the variable on the left.” It differs from the equality operator:

Code	Meaning
`score = 10;`	Change `score` to 10
`score == 10`	Produce true when `score` equals 10

Use the previous value

The right side is evaluated before the new value is stored:

score = score + 5;

If score held 10, it now holds 15.

Sugar provides assignment shortcuts for common number changes:

Shortcut	Equivalent assignment
`score += 5;`	`score = score + 5;`
`health -= 10;`	`health = health - 10;`
`reward *= 2;`	`reward = reward * 2;`
`total /= 4;`	`total = total / 4;`
`wins++;`	`wins = wins + 1;`
`lives--;`	`lives = lives - 1;`

Read the changed value

Later statements see the new value:

var score = 10;

text {
  score += 5;
  "Your score is now {score}."
}

The message says Your score is now 15.

Which names may be assigned?

var and let declare mutable variables, so both may be assigned while they are in scope. A const is calculated and read-only, so assigning one is an error.

The assignment above lasts until the current use finishes. On the next use, a regular var starts from its initial value again. A later lesson adds mem when a variable must remember its changed value.

The next lesson uses assignments inside if and else branches.