A rational number can be represented as a pair of integer numbers: a/b (b>0), where a is the numerator and b is the denominator. Integer
a equals rational a/1 mathematically.
In Ruby, you can create rational objects with the Kernel#Rational, to_r
, or rationalize methods or by suffixing r
to a literal. The return values will be irreducible fractions.
Rational(1) #=> (1/1) Rational(2, 3) #=> (2/3) Rational(4, -6) #=> (-2/3) 3.to_r #=> (3/1) 2/3r #=> (2/3)
You can also create rational objects from floating-point numbers or strings.
Rational(0.3) #=> (5404319552844595/18014398509481984) Rational('0.3') #=> (3/10) Rational('2/3') #=> (2/3) 0.3.to_r #=> (5404319552844595/18014398509481984) '0.3'.to_r #=> (3/10) '2/3'.to_r #=> (2/3) 0.3.rationalize #=> (3/10)
A rational object is an exact number, which helps you to write programs without any rounding errors.
10.times.inject(0) {|t| t + 0.1 } #=> 0.9999999999999999 10.times.inject(0) {|t| t + Rational('0.1') } #=> (1/1)
However, when an expression includes an inexact component (numerical value or operation), it will produce an inexact result.
Rational(10) / 3 #=> (10/3) Rational(10) / 3.0 #=> 3.3333333333333335 Rational(-8) ** Rational(1, 3) #=> (1.0000000000000002+1.7320508075688772i)
Performs multiplication.
Rational(2, 3) * Rational(2, 3) #=> (4/9) Rational(900) * Rational(1) #=> (900/1) Rational(-2, 9) * Rational(-9, 2) #=> (1/1) Rational(9, 8) * 4 #=> (9/2) Rational(20, 9) * 9.8 #=> 21.77777777777778
static VALUE nurat_mul(VALUE self, VALUE other) { if (RB_INTEGER_TYPE_P(other)) { { get_dat1(self); return f_muldiv(self, dat->num, dat->den, other, ONE, '*'); } } else if (RB_FLOAT_TYPE_P(other)) { return DBL2NUM(nurat_to_double(self) * RFLOAT_VALUE(other)); } else if (RB_TYPE_P(other, T_RATIONAL)) { { get_dat2(self, other); return f_muldiv(self, adat->num, adat->den, bdat->num, bdat->den, '*'); } } else { return rb_num_coerce_bin(self, other, '*'); } }
Performs exponentiation.
Rational(2) ** Rational(3) #=> (8/1) Rational(10) ** -2 #=> (1/100) Rational(10) ** -2.0 #=> 0.01 Rational(-4) ** Rational(1, 2) #=> (0.0+2.0i) Rational(1, 2) ** 0 #=> (1/1) Rational(1, 2) ** 0.0 #=> 1.0
static VALUE nurat_expt(VALUE self, VALUE other) { if (k_numeric_p(other) && k_exact_zero_p(other)) return f_rational_new_bang1(CLASS_OF(self), ONE); if (k_rational_p(other)) { get_dat1(other); if (f_one_p(dat->den)) other = dat->num; /* c14n */ } /* Deal with special cases of 0**n and 1**n */ if (k_numeric_p(other) && k_exact_p(other)) { get_dat1(self); if (f_one_p(dat->den)) { if (f_one_p(dat->num)) { return f_rational_new_bang1(CLASS_OF(self), ONE); } else if (f_minus_one_p(dat->num) && RB_INTEGER_TYPE_P(other)) { return f_rational_new_bang1(CLASS_OF(self), INT2FIX(f_odd_p(other) ? -1 : 1)); } else if (INT_ZERO_P(dat->num)) { if (rb_num_negative_p(other)) { rb_num_zerodiv(); } else { return f_rational_new_bang1(CLASS_OF(self), ZERO); } } } } /* General case */ if (FIXNUM_P(other)) { { VALUE num, den; get_dat1(self); if (INT_POSITIVE_P(other)) { num = rb_int_pow(dat->num, other); den = rb_int_pow(dat->den, other); } else if (INT_NEGATIVE_P(other)) { num = rb_int_pow(dat->den, rb_int_uminus(other)); den = rb_int_pow(dat->num, rb_int_uminus(other)); } else { num = ONE; den = ONE; } if (RB_FLOAT_TYPE_P(num)) { /* infinity due to overflow */ if (RB_FLOAT_TYPE_P(den)) return DBL2NUM(NAN); return num; } if (RB_FLOAT_TYPE_P(den)) { /* infinity due to overflow */ num = ZERO; den = ONE; } return f_rational_new2(CLASS_OF(self), num, den); } } else if (RB_TYPE_P(other, T_BIGNUM)) { rb_warn("in a**b, b may be too big"); return rb_float_pow(nurat_to_f(self), other); } else if (RB_FLOAT_TYPE_P(other) || RB_TYPE_P(other, T_RATIONAL)) { return rb_float_pow(nurat_to_f(self), other); } else { return rb_num_coerce_bin(self, other, rb_intern("**")); } }
Performs addition.
Rational(2, 3) + Rational(2, 3) #=> (4/3) Rational(900) + Rational(1) #=> (901/1) Rational(-2, 9) + Rational(-9, 2) #=> (-85/18) Rational(9, 8) + 4 #=> (41/8) Rational(20, 9) + 9.8 #=> 12.022222222222222
VALUE rb_rational_plus(VALUE self, VALUE other) { if (RB_INTEGER_TYPE_P(other)) { { get_dat1(self); return f_rational_new_no_reduce2(CLASS_OF(self), rb_int_plus(dat->num, rb_int_mul(other, dat->den)), dat->den); } } else if (RB_FLOAT_TYPE_P(other)) { return DBL2NUM(nurat_to_double(self) + RFLOAT_VALUE(other)); } else if (RB_TYPE_P(other, T_RATIONAL)) { { get_dat2(self, other); return f_addsub(self, adat->num, adat->den, bdat->num, bdat->den, '+'); } } else { return rb_num_coerce_bin(self, other, '+'); } }
Performs subtraction.
Rational(2, 3) - Rational(2, 3) #=> (0/1) Rational(900) - Rational(1) #=> (899/1) Rational(-2, 9) - Rational(-9, 2) #=> (77/18) Rational(9, 8) - 4 #=> (-23/8) Rational(20, 9) - 9.8 #=> -7.577777777777778
static VALUE nurat_sub(VALUE self, VALUE other) { if (RB_INTEGER_TYPE_P(other)) { { get_dat1(self); return f_rational_new_no_reduce2(CLASS_OF(self), rb_int_minus(dat->num, rb_int_mul(other, dat->den)), dat->den); } } else if (RB_FLOAT_TYPE_P(other)) { return DBL2NUM(nurat_to_double(self) - RFLOAT_VALUE(other)); } else if (RB_TYPE_P(other, T_RATIONAL)) { { get_dat2(self, other); return f_addsub(self, adat->num, adat->den, bdat->num, bdat->den, '-'); } } else { return rb_num_coerce_bin(self, other, '-'); } }
Negates rat
.
VALUE rb_rational_uminus(VALUE self) { const int unused = (assert(RB_TYPE_P(self, T_RATIONAL)), 0); get_dat1(self); (void)unused; return f_rational_new2(CLASS_OF(self), rb_int_uminus(dat->num), dat->den); }
Performs division.
Rational(2, 3) / Rational(2, 3) #=> (1/1) Rational(900) / Rational(1) #=> (900/1) Rational(-2, 9) / Rational(-9, 2) #=> (4/81) Rational(9, 8) / 4 #=> (9/32) Rational(20, 9) / 9.8 #=> 0.22675736961451246
static VALUE nurat_div(VALUE self, VALUE other) { if (RB_INTEGER_TYPE_P(other)) { if (f_zero_p(other)) rb_num_zerodiv(); { get_dat1(self); return f_muldiv(self, dat->num, dat->den, other, ONE, '/'); } } else if (RB_FLOAT_TYPE_P(other)) return DBL2NUM(nurat_to_double(self) / RFLOAT_VALUE(other)); else if (RB_TYPE_P(other, T_RATIONAL)) { if (f_zero_p(other)) rb_num_zerodiv(); { get_dat2(self, other); if (f_one_p(self)) return f_rational_new_no_reduce2(CLASS_OF(self), bdat->den, bdat->num); return f_muldiv(self, adat->num, adat->den, bdat->num, bdat->den, '/'); } } else { return rb_num_coerce_bin(self, other, '/'); } }
Returns -1, 0, or +1 depending on whether rational
is less than, equal to, or greater than numeric
.
nil
is returned if the two values are incomparable.
Rational(2, 3) <=> Rational(2, 3) #=> 0 Rational(5) <=> 5 #=> 0 Rational(2, 3) <=> Rational(1, 3) #=> 1 Rational(1, 3) <=> 1 #=> -1 Rational(1, 3) <=> 0.3 #=> 1 Rational(1, 3) <=> "0.3" #=> nil
VALUE rb_rational_cmp(VALUE self, VALUE other) { if (RB_INTEGER_TYPE_P(other)) { { get_dat1(self); if (dat->den == LONG2FIX(1)) return rb_int_cmp(dat->num, other); /* c14n */ other = f_rational_new_bang1(CLASS_OF(self), other); goto other_is_rational; } } else if (RB_FLOAT_TYPE_P(other)) { return rb_dbl_cmp(nurat_to_double(self), RFLOAT_VALUE(other)); } else if (RB_TYPE_P(other, T_RATIONAL)) { other_is_rational: { VALUE num1, num2; get_dat2(self, other); if (FIXNUM_P(adat->num) && FIXNUM_P(adat->den) && FIXNUM_P(bdat->num) && FIXNUM_P(bdat->den)) { num1 = f_imul(FIX2LONG(adat->num), FIX2LONG(bdat->den)); num2 = f_imul(FIX2LONG(bdat->num), FIX2LONG(adat->den)); } else { num1 = rb_int_mul(adat->num, bdat->den); num2 = rb_int_mul(bdat->num, adat->den); } return rb_int_cmp(rb_int_minus(num1, num2), ZERO); } } else { return rb_num_coerce_cmp(self, other, rb_intern("<=>")); } }
Returns true
if rat
equals object
numerically.
Rational(2, 3) == Rational(2, 3) #=> true Rational(5) == 5 #=> true Rational(0) == 0.0 #=> true Rational('1/3') == 0.33 #=> false Rational('1/2') == '1/2' #=> false
static VALUE nurat_eqeq_p(VALUE self, VALUE other) { if (RB_INTEGER_TYPE_P(other)) { { get_dat1(self); if (INT_ZERO_P(dat->num) && INT_ZERO_P(other)) return Qtrue; if (!FIXNUM_P(dat->den)) return Qfalse; if (FIX2LONG(dat->den) != 1) return Qfalse; return rb_int_equal(dat->num, other); } } else if (RB_FLOAT_TYPE_P(other)) { const double d = nurat_to_double(self); return f_boolcast(FIXNUM_ZERO_P(rb_dbl_cmp(d, RFLOAT_VALUE(other)))); } else if (RB_TYPE_P(other, T_RATIONAL)) { { get_dat2(self, other); if (INT_ZERO_P(adat->num) && INT_ZERO_P(bdat->num)) return Qtrue; return f_boolcast(rb_int_equal(adat->num, bdat->num) && rb_int_equal(adat->den, bdat->den)); } } else { return rb_equal(other, self); } }
Returns the absolute value of rat
.
(1/2r).abs #=> (1/2) (-1/2r).abs #=> (1/2)
Rational#magnitude
is an alias for Rational#abs
.
VALUE rb_rational_abs(VALUE self) { get_dat1(self); if (INT_NEGATIVE_P(dat->num)) { VALUE num = rb_int_abs(dat->num); return nurat_s_canonicalize_internal_no_reduce(CLASS_OF(self), num, dat->den); } return self; }
Returns the smallest number greater than or equal to rat
with a precision of ndigits
decimal digits (default: 0).
When the precision is negative, the returned value is an integer with at least ndigits.abs
trailing zeros.
Returns a rational when ndigits
is positive, otherwise returns an integer.
Rational(3).ceil #=> 3 Rational(2, 3).ceil #=> 1 Rational(-3, 2).ceil #=> -1 # decimal - 1 2 3 . 4 5 6 # ^ ^ ^ ^ ^ ^ # precision -3 -2 -1 0 +1 +2 Rational('-123.456').ceil(+1).to_f #=> -123.4 Rational('-123.456').ceil(-1) #=> -120
static VALUE nurat_ceil_n(int argc, VALUE *argv, VALUE self) { return f_round_common(argc, argv, self, nurat_ceil); }
Returns the denominator (always positive).
Rational(7).denominator #=> 1 Rational(7, 1).denominator #=> 1 Rational(9, -4).denominator #=> 4 Rational(-2, -10).denominator #=> 5
static VALUE nurat_denominator(VALUE self) { get_dat1(self); return dat->den; }
Performs division and returns the value as a Float
.
Rational(2, 3).fdiv(1) #=> 0.6666666666666666 Rational(2, 3).fdiv(0.5) #=> 1.3333333333333333 Rational(2).fdiv(3) #=> 0.6666666666666666
static VALUE nurat_fdiv(VALUE self, VALUE other) { VALUE div; if (f_zero_p(other)) return DBL2NUM(nurat_to_double(self) / 0.0); if (FIXNUM_P(other) && other == LONG2FIX(1)) return nurat_to_f(self); div = nurat_div(self, other); if (RB_TYPE_P(div, T_RATIONAL)) return nurat_to_f(div); if (RB_FLOAT_TYPE_P(div)) return div; return rb_funcall(div, rb_intern("to_f"), 0); }
Returns the largest number less than or equal to rat
with a precision of ndigits
decimal digits (default: 0).
When the precision is negative, the returned value is an integer with at least ndigits.abs
trailing zeros.
Returns a rational when ndigits
is positive, otherwise returns an integer.
Rational(3).floor #=> 3 Rational(2, 3).floor #=> 0 Rational(-3, 2).floor #=> -2 # decimal - 1 2 3 . 4 5 6 # ^ ^ ^ ^ ^ ^ # precision -3 -2 -1 0 +1 +2 Rational('-123.456').floor(+1).to_f #=> -123.5 Rational('-123.456').floor(-1) #=> -130
static VALUE nurat_floor_n(int argc, VALUE *argv, VALUE self) { return f_round_common(argc, argv, self, nurat_floor); }
Returns the value as a string for inspection.
Rational(2).inspect #=> "(2/1)" Rational(-8, 6).inspect #=> "(-4/3)" Rational('1/2').inspect #=> "(1/2)"
static VALUE nurat_inspect(VALUE self) { VALUE s; s = rb_usascii_str_new2("("); rb_str_concat(s, f_format(self, f_inspect)); rb_str_cat2(s, ")"); return s; }
Returns the absolute value of rat
.
(1/2r).abs #=> (1/2) (-1/2r).abs #=> (1/2)
Rational#magnitude
is an alias for Rational#abs
.
VALUE rb_rational_abs(VALUE self) { get_dat1(self); if (INT_NEGATIVE_P(dat->num)) { VALUE num = rb_int_abs(dat->num); return nurat_s_canonicalize_internal_no_reduce(CLASS_OF(self), num, dat->den); } return self; }
Returns true
if rat
is less than 0.
static VALUE nurat_negative_p(VALUE self) { get_dat1(self); return f_boolcast(INT_NEGATIVE_P(dat->num)); }
Returns the numerator.
Rational(7).numerator #=> 7 Rational(7, 1).numerator #=> 7 Rational(9, -4).numerator #=> -9 Rational(-2, -10).numerator #=> 1
static VALUE nurat_numerator(VALUE self) { get_dat1(self); return dat->num; }
Returns true
if rat
is greater than 0.
static VALUE nurat_positive_p(VALUE self) { get_dat1(self); return f_boolcast(INT_POSITIVE_P(dat->num)); }
Performs division.
Rational(2, 3) / Rational(2, 3) #=> (1/1) Rational(900) / Rational(1) #=> (900/1) Rational(-2, 9) / Rational(-9, 2) #=> (4/81) Rational(9, 8) / 4 #=> (9/32) Rational(20, 9) / 9.8 #=> 0.22675736961451246
static VALUE nurat_div(VALUE self, VALUE other) { if (RB_INTEGER_TYPE_P(other)) { if (f_zero_p(other)) rb_num_zerodiv(); { get_dat1(self); return f_muldiv(self, dat->num, dat->den, other, ONE, '/'); } } else if (RB_FLOAT_TYPE_P(other)) return DBL2NUM(nurat_to_double(self) / RFLOAT_VALUE(other)); else if (RB_TYPE_P(other, T_RATIONAL)) { if (f_zero_p(other)) rb_num_zerodiv(); { get_dat2(self, other); if (f_one_p(self)) return f_rational_new_no_reduce2(CLASS_OF(self), bdat->den, bdat->num); return f_muldiv(self, adat->num, adat->den, bdat->num, bdat->den, '/'); } } else { return rb_num_coerce_bin(self, other, '/'); } }
Returns a simpler approximation of the value if the optional argument eps
is given (rat-|eps| <= result <= rat+|eps|), self otherwise.
r = Rational(5033165, 16777216) r.rationalize #=> (5033165/16777216) r.rationalize(Rational('0.01')) #=> (3/10) r.rationalize(Rational('0.1')) #=> (1/3)
static VALUE nurat_rationalize(int argc, VALUE *argv, VALUE self) { VALUE e, a, b, p, q; if (argc == 0) return self; if (nurat_negative_p(self)) return rb_rational_uminus(nurat_rationalize(argc, argv, rb_rational_uminus(self))); rb_scan_args(argc, argv, "01", &e); e = f_abs(e); a = f_sub(self, e); b = f_add(self, e); if (f_eqeq_p(a, b)) return self; nurat_rationalize_internal(a, b, &p, &q); return f_rational_new2(CLASS_OF(self), p, q); }
Returns rat
rounded to the nearest value with a precision of ndigits
decimal digits (default: 0).
When the precision is negative, the returned value is an integer with at least ndigits.abs
trailing zeros.
Returns a rational when ndigits
is positive, otherwise returns an integer.
Rational(3).round #=> 3 Rational(2, 3).round #=> 1 Rational(-3, 2).round #=> -2 # decimal - 1 2 3 . 4 5 6 # ^ ^ ^ ^ ^ ^ # precision -3 -2 -1 0 +1 +2 Rational('-123.456').round(+1).to_f #=> -123.5 Rational('-123.456').round(-1) #=> -120
The optional half
keyword argument is available similar to Float#round
.
Rational(25, 100).round(1, half: :up) #=> (3/10) Rational(25, 100).round(1, half: :down) #=> (1/5) Rational(25, 100).round(1, half: :even) #=> (1/5) Rational(35, 100).round(1, half: :up) #=> (2/5) Rational(35, 100).round(1, half: :down) #=> (3/10) Rational(35, 100).round(1, half: :even) #=> (2/5) Rational(-25, 100).round(1, half: :up) #=> (-3/10) Rational(-25, 100).round(1, half: :down) #=> (-1/5) Rational(-25, 100).round(1, half: :even) #=> (-1/5)
static VALUE nurat_round_n(int argc, VALUE *argv, VALUE self) { VALUE opt; enum ruby_num_rounding_mode mode = ( argc = rb_scan_args(argc, argv, "*:", NULL, &opt), rb_num_get_rounding_option(opt)); VALUE (*round_func)(VALUE) = ROUND_FUNC(mode, nurat_round); return f_round_common(argc, argv, self, round_func); }
Returns the value as a Float
.
Rational(2).to_f #=> 2.0 Rational(9, 4).to_f #=> 2.25 Rational(-3, 4).to_f #=> -0.75 Rational(20, 3).to_f #=> 6.666666666666667
static VALUE nurat_to_f(VALUE self) { return DBL2NUM(nurat_to_double(self)); }
Returns the truncated value as an integer.
Equivalent to Rational#truncate
.
Rational(2, 3).to_i #=> 0 Rational(3).to_i #=> 3 Rational(300.6).to_i #=> 300 Rational(98, 71).to_i #=> 1 Rational(-31, 2).to_i #=> -15
static VALUE nurat_truncate(VALUE self) { get_dat1(self); if (INT_NEGATIVE_P(dat->num)) return rb_int_uminus(rb_int_idiv(rb_int_uminus(dat->num), dat->den)); return rb_int_idiv(dat->num, dat->den); }
Returns self.
Rational(2).to_r #=> (2/1) Rational(-8, 6).to_r #=> (-4/3)
static VALUE nurat_to_r(VALUE self) { return self; }
Returns the value as a string.
Rational(2).to_s #=> "2/1" Rational(-8, 6).to_s #=> "-4/3" Rational('1/2').to_s #=> "1/2"
static VALUE nurat_to_s(VALUE self) { return f_format(self, f_to_s); }
Returns rat
truncated (toward zero) to a precision of ndigits
decimal digits (default: 0).
When the precision is negative, the returned value is an integer with at least ndigits.abs
trailing zeros.
Returns a rational when ndigits
is positive, otherwise returns an integer.
Rational(3).truncate #=> 3 Rational(2, 3).truncate #=> 0 Rational(-3, 2).truncate #=> -1 # decimal - 1 2 3 . 4 5 6 # ^ ^ ^ ^ ^ ^ # precision -3 -2 -1 0 +1 +2 Rational('-123.456').truncate(+1).to_f #=> -123.4 Rational('-123.456').truncate(-1) #=> -120
static VALUE nurat_truncate_n(int argc, VALUE *argv, VALUE self) { return f_round_common(argc, argv, self, nurat_truncate); }