Method: Kernel#rand

Defined in:

random.c

#rand(max = 0) ⇒ Numeric

If called without an argument, or if max.to_i.abs == 0, rand returns a pseudo-random floating point number between 0.0 and 1.0, including 0.0 and excluding 1.0.

rand        #=> 0.2725926052826416

When max.abs is greater than or equal to 1, rand returns a pseudo-random integer greater than or equal to 0 and less than max.to_i.abs.

rand(100)   #=> 12

When max is a Range, rand returns a random number where range.member?(number) == true.

Negative or floating point values for max are allowed, but may give surprising results.

rand(-100) # => 87
rand(-0.5) # => 0.8130921818028143
rand(1.9)  # equivalent to rand(1), which is always 0

Kernel.srand may be used to ensure that sequences of random numbers are reproducible between different runs of a program.

See also Random.rand.

Returns:

• (Numeric)

# File 'random.c', line 1362

static VALUE
rb_f_rand(int argc, VALUE *argv, VALUE obj)
{
    VALUE vmax;
    rb_random_t *rnd = rand_start(&default_rand);

    if (rb_check_arity(argc, 0, 1) && !NIL_P(vmax = argv[0])) {
	VALUE v = rand_range(Qnil, rnd, vmax);
	if (v != Qfalse) return v;
	vmax = rb_to_int(vmax);
	if (vmax != INT2FIX(0)) {
	    v = rand_int(Qnil, rnd, vmax, 0);
	    if (!NIL_P(v)) return v;
	}
    }
    return DBL2NUM(genrand_real(&rnd->mt));
}