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instance method

Module#<=>

(untyped other) -> (-1 | 0 | 1)?

self <=> other → -1, 0, 1, or nil

static VALUE
rb_mod_cmp(VALUE mod, VALUE arg)
{
    VALUE cmp;

    if (mod == arg) return INT2FIX(0);
    if (!CLASS_OR_MODULE_P(arg)) {
        return Qnil;
    }

    cmp = rb_class_inherited_p(mod, arg);
    if (NIL_P(cmp)) return Qnil;
    if (cmp) {
        return INT2FIX(-1);
    }
    return INT2FIX(1);
}

Compares self and other.

Returns:

-1, if self includes other, if or self is a subclass of other.
0, if self and other are the same.
1, if other includes self, or if other is a subclass of self.
nil, if none of the above is true.

Examples:

Example

# Class Array includes module Enumerable.
         Array <=> Enumerable # => -1
    Enumerable <=> Enumerable # =>  0
    Enumerable <=> Array      # =>  1
# Class File is a subclass of class IO.
          File <=> IO         # => -1
          File <=> File       # =>  0
            IO <=> File       # =>  1
# Class File has no relationship to class String.
          File <=> String     # => nil

See also #<= #== #< #=== also in 4.0 · 3.4 · 3.3 · 3.2 · 3.1 · 3.0

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