method

rationalize

v1_9_3_392 - Show latest stable - Class: Float

rationalize(p1 = v1)

public

Returns a simpler approximation of the value (flt-|eps| <= result <= flt+|eps|). if eps is not given, it will be chosen automatically.

For example:

0.3.rationalize          #=> (3/10)
1.333.rationalize        #=> (1333/1000)
1.333.rationalize(0.01)  #=> (4/3)

static VALUE
float_rationalize(int argc, VALUE *argv, VALUE self)
{
    VALUE e, a, b, p, q;

    if (f_negative_p(self))
        return f_negate(float_rationalize(argc, argv, f_abs(self)));

    rb_scan_args(argc, argv, "01", &e);

    if (argc != 0) {
        e = f_abs(e);
        a = f_sub(self, e);
        b = f_add(self, e);
    }
    else {
        VALUE f, n;

        float_decode_internal(self, &f, &n);
        if (f_zero_p(f) || f_positive_p(n))
            return rb_rational_new1(f_lshift(f, n));

#if FLT_RADIX == 2
        a = rb_rational_new2(f_sub(f_mul(TWO, f), ONE),
                             f_lshift(ONE, f_sub(ONE, n)));
        b = rb_rational_new2(f_add(f_mul(TWO, f), ONE),
                             f_lshift(ONE, f_sub(ONE, n)));
#else
        a = rb_rational_new2(f_sub(f_mul(INT2FIX(FLT_RADIX), f),
                                   INT2FIX(FLT_RADIX - 1)),
                             f_expt(INT2FIX(FLT_RADIX), f_sub(ONE, n)));
        b = rb_rational_new2(f_add(f_mul(INT2FIX(FLT_RADIX), f),
                                   INT2FIX(FLT_RADIX - 1)),
                             f_expt(INT2FIX(FLT_RADIX), f_sub(ONE, n)));
#endif
    }

    if (f_eqeq_p(a, b))
        return f_to_r(self);

    nurat_rationalize_internal(a, b, &p, &q);
    return rb_rational_new2(p, q);
}

rationalize

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