method

rand

v1_9_3_125 - Show latest stable - 0 notes - Class: Random

rand(*args) public

When the argument is an Integer or a Bignum, it returns a random integer greater than or equal to zero and less than the argument. Unlike Random.rand, when the argument is a negative integer or zero, it raises an ArgumentError.

When the argument is a Float, it returns a random floating point number between 0.0 and max, including 0.0 and excluding max.

When the argument limit is a Range, it returns a random number where range.member?(number) == true.

prng.rand(5..9)  #=> one of [5, 6, 7, 8, 9]
prng.rand(5...9) #=> one of [5, 6, 7, 8]
prng.rand(5.0..9.0) #=> between 5.0 and 9.0, including 9.0
prng.rand(5.0...9.0) #=> between 5.0 and 9.0, excluding 9.0

begin/end of the range have to have subtract and add methods.

Otherwise, it raises an ArgumentError.

Show source

static VALUE
random_rand(int argc, VALUE *argv, VALUE obj)
{
    rb_random_t *rnd = get_rnd(obj);
    VALUE vmax, v;

    if (argc == 0) {
        return rb_float_new(genrand_real(&rnd->mt));
    }
    else if (argc != 1) {
        rb_raise(rb_eArgError, "wrong number of arguments (%d for 0..1)", argc);
    }
    vmax = argv[0];
    if (NIL_P(vmax)) {
        v = Qnil;
    }
    else if (TYPE(vmax) != T_FLOAT && (v = rb_check_to_integer(vmax, "to_int"), !NIL_P(v))) {
        v = rand_int(&rnd->mt, v, 1);
    }
    else if (v = rb_check_to_float(vmax), !NIL_P(v)) {
        double max = float_value(v);
        if (max > 0.0)
            v = rb_float_new(max * genrand_real(&rnd->mt));
        else
            v = Qnil;
    }
    else if ((v = rand_range(&rnd->mt, vmax)) != Qfalse) {
        /* nothing to do */
    }
    else {
        v = Qnil;
        (void)NUM2LONG(vmax);
    }
    if (NIL_P(v)) {
        VALUE mesg = rb_str_new_cstr("invalid argument - ");
        rb_str_append(mesg, rb_obj_as_string(argv[0]));
        rb_exc_raise(rb_exc_new3(rb_eArgError, mesg));
    }

    return v;
}

rand

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