The Ruby Programming Language

Operators

An operator is a token in the Ruby language that represents an operation (such as addition or comparison) to be performed on one or more operands. The operands are expressions, and operators allow us to combine these operand expressions into larger expressions. The numeric literal 2 and the operator +, for example, can be combined into the expression 2+2. And the following expression combines a numeric literal, a method invocation expression, and a variable reference expression with the multiplication operator and the less-than operator:

2 * Math.sqrt(2) < limit

Table 4-2 later in this section summarizes each of Ruby’s operators, and the sections that follow describe each one in detail. To fully understand operators, however, you need to understand operator arity, precedence, and associativity.

The arity of an operator is the number of operands it operates on. Unary operators expect a single operand. Binary operators expect two operands. Ternary operators (there is only one of these) expect three operands. The arity of each operator is listed in column N of Table 4-2. Note that the operators + and – have both unary and binary forms.

The precedence of an operator specifies how “tightly” an operator is bound to its operands, and affects the order of evaluation of an expression. Consider this expression, for example:

1 + 2 * 3     # => 7

The multiplication operator has higher precedence than the addition operator, so the multiplication is performed first and the expression evaluates ...