Object#<=>

obj <=> other → 0 or nil

static VALUE
rb_obj_cmp(VALUE obj1, VALUE obj2)
{
    if (rb_equal(obj1, obj2))
        return INT2FIX(0);
    return Qnil;
}

Returns 0 if obj and other are the same object or obj == other, otherwise nil.

The <=> is used by various methods to compare objects, for example Enumerable#sort, Enumerable#max etc.

Your implementation of <=> should return one of the following values: -1, 0, 1 or nil. -1 means self is smaller than other. 0 means self is equal to other. 1 means self is bigger than other. Nil means the two values could not be compared.

When you define <=>, you can include Comparable to gain the methods <=, <, ==, >=, > and between?.

See also #!~ #=== .yaml_tag #CSV also in 4.1 · 4.0 · 3.4 · 3.2 · 3.1 · 3.0

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