Operators

Available operators

Operator	Description
=	Assignment
? :	Ternary conditional
and, &&	Logical and
or, ||	Logical or
==, !=	Equal, not equal
<, >, <=, >=	Comparison
+, -	Addition, subtraction
*, /	Multiplication, division
%	Modulo
-, !	Prefix negation, prefix not
()	Call
.	Member access
[]	Index

and and && are the same operator, as are or and ||. Pick one style and keep to it within a file; the word forms read more naturally in conditions, and the symbol forms are shorter in dense expressions.

Division

Dividing two integers gives an integer, as in Ruby. The result is truncated toward zero rather than rounded.

puts(4 / 2)   // 2
puts(5 / 2)   // 2, not 2.5

Mixing an integer with a float promotes the result to a float, so make one side a float when you want the fractional part:

puts(4.0 / 2)   // 2.0
puts(4 / 2.0)   // 2.0
puts(5 / 2.0)   // 2.5

Truncation means a negative quotient rounds toward zero: -5 / 2 is -2, not -3. This keeps division consistent with %, whose sign follows the dividend, so (a / b) * b + a % b always gives back a.

Dividing by zero is an error in both forms.

Precedence

Operators lower in this table bind more tightly, so they are applied first.

	Operators	Example
1	=	a = 1 + 2 assigns 3
2	? :	a == 1 ? "y" : "n"
3	and, &&, or, ||	see the note below
4	==, !=	2 + 3 == 5 is true
5	<, >, <=, >=	1 < 2 and 3 > 2 is true
6	+, -
7	*, /	1 + 2 * 3 is 7
8	%	2 * 10 % 4 is 4
9	prefix -, !	-2 * 3 is -6
10	(), .
11	[]

Parentheses override all of it: (1 + 2) * 3 is 9.

Note that % binds more tightly than * and /, which is not true in every language. 2 * 10 % 4 groups as 2 * (10 % 4), giving 4 rather than 0.

and and or share one level

Unlike most languages, and does not bind more tightly than or. They sit at the same precedence and group left to right, so:

true or false and false

is (true or false) and false, which is false — not true or (false and false), which would be true. Parenthesise whenever a condition mixes the two:

puts(true or (false and false))  // true
puts((true or false) and false)  // false