Sharedsupport / 2016-01-18-110500-docs-exact-rational.sagewsOpen in CoCalc
Authors: Harald Schilly, ℏal Snyder, William A. Stein
License: GNU General Public License v3.0
Description: Examples for support purposes.
(1.0).exact_rational?
File: /projects/sage/sage-6.10/src/sage/rings/real_mpfr.pyx Signature : (RealNumber('1.0')).exact_rational() Docstring : Returns the exact rational representation of this floating-point number. EXAMPLES: sage: RR(0).exact_rational() 0 sage: RR(1/3).exact_rational() 6004799503160661/18014398509481984 sage: RR(37/16).exact_rational() 37/16 sage: RR(3^60).exact_rational() 42391158275216203520420085760 sage: RR(3^60).exact_rational() - 3^60 6125652559 sage: RealField(5)(-pi).exact_rational() -25/8
(1.0).exact_rational??
File: /projects/sage/sage-6.10/src/sage/rings/real_mpfr.pyx Source: def exact_rational(self): """ Returns the exact rational representation of this floating-point number. EXAMPLES:: sage: RR(0).exact_rational() 0 sage: RR(1/3).exact_rational() 6004799503160661/18014398509481984 sage: RR(37/16).exact_rational() 37/16 sage: RR(3^60).exact_rational() 42391158275216203520420085760 sage: RR(3^60).exact_rational() - 3^60 6125652559 sage: RealField(5)(-pi).exact_rational() -25/8 TESTS:: sage: RR('nan').exact_rational() Traceback (most recent call last): ... ValueError: Cannot convert NaN or infinity to rational number sage: RR('-infinity').exact_rational() Traceback (most recent call last): ... ValueError: Cannot convert NaN or infinity to rational number """ if not mpfr_number_p(self.value): raise ValueError, 'Cannot convert NaN or infinity to rational number' cdef Integer mantissa = Integer() cdef mp_exp_t exponent if mpfr_sgn(self.value) == 0: return Rational(0) exponent = mpfr_get_z_exp(mantissa.value, self.value) return Rational(mantissa) * Integer(2) ** exponent