method

rand

v1_9_2_180 - 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, beg = Qundef, v;
    int excl = 0;

    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, vmax = 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 = range_values(vmax, &beg, &excl)) != Qfalse) {
        vmax = v;
        if (TYPE(vmax) != T_FLOAT && (v = rb_check_to_integer(vmax, "to_int"), !NIL_P(v))) {
            long max;
            vmax = v;
            v = Qnil;
            if (FIXNUM_P(vmax)) {
              fixnum:
                if ((max = FIX2LONG(vmax) - excl) >= 0) {
                    unsigned long r = limited_rand(&rnd->mt, (unsigned long)max);
                    v = ULONG2NUM(r);
                }
            }
            else if (BUILTIN_TYPE(vmax) == T_BIGNUM && RBIGNUM_SIGN(vmax) && !rb_bigzero_p(vmax)) {
                vmax = excl ? rb_big_minus(vmax, INT2FIX(1)) : rb_big_norm(vmax);
                if (FIXNUM_P(vmax)) {
                    excl = 0;
                    goto fixnum;
                }
                v = limited_big_rand(&rnd->mt, RBIGNUM(vmax));
            }
        }
        else if (v = rb_check_to_float(vmax), !NIL_P(v)) {
            double max = float_value(v), r;
            v = Qnil;
            if (max > 0.0) {
                if (excl) {
                    r = genrand_real(&rnd->mt);
                }
                else {
                    r = genrand_real2(&rnd->mt);
                }
                v = rb_float_new(r * max);
            }
            else if (max == 0.0 && !excl) {
                v = rb_float_new(0.0);
            }
        }
    }
    else {
        v = Qnil;
        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));
    }
    if (beg == Qundef) return v;
    if (FIXNUM_P(beg) && FIXNUM_P(v)) {
        long x = FIX2LONG(beg) + FIX2LONG(v);
        return LONG2NUM(x);
    }
    switch (TYPE(v)) {
      case T_BIGNUM:
        return rb_big_plus(v, beg);
      case T_FLOAT: {
        VALUE f = rb_check_to_float(beg);
        if (!NIL_P(f)) {
            RFLOAT_VALUE(v) += RFLOAT_VALUE(f);
            return v;
        }
      }
      default:
        return rb_funcall2(beg, id_plus, 1, &v);
    }
}

rand

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