►Pyret
▼2 Language Concepts
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2.4 Operator Precedence

Pyret does not use implicit operator precedence or the order of operations that you learned in math class. “Please Excuse My Dear Aunt Sally” does not apply here.

Note for non-American readers: if you’ve never heard of dear Aunt Sally, it’s a mnemonic often used to memorize a standard order-of-operations.

Pyret disallows mixing operators without clearly defining the operator precedence using parentheses. This includes all Binary Operators.

Therefore, the following expressions are not allowed:

1 + 1 - 1
1 + 1 > 1
1 + 1 == 2
(3 * 4 / 2)
(3 * 4) / 1 + 1
3 * (4 / 2) + 1

And will raise an error like:

Conversely, these expressions are all valid in Pyret:

Any number of identical operators can be grouped without pairwise parentheses.

1 + (1 - 1)
(1 + 1) > 1
1 + 1 + 1
1 - 1 - 1
(1 + 1) == 2
3 * (4 / 2)
(3 * (4 / 2))
(3 * 4) / (1 + 1)
(3 * (4 / 2)) + 1

Implicit operator precedence is a common source of errors among even experienced developers, so getting in the habit of explicitly defining precedence using parentheses is a good idea even when using languages that support implicit precedence.

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