C++ Interface Rationals (GNU MP 6.3.0)
Description: How to install and use the GNU multiple precision arithmetic library, version 6.3.0.

### 12.3 C++ Interface Rationals

In all the following constructors, if a fraction is given then it should be in canonical form, or if not then `mpq_class::canonicalize` called.

Function: mpq_class::mpq_class `(type op)` ¶
Function: mpq_class::mpq_class `(integer num, integer den)` ¶

  Construct an `mpq_class`. The initial value can be a single value of any type (conversion from `mpf_class` is `explicit`), or a pair of integers (`mpz_class` or standard C++ integer types) representing a fraction, except that `long long` and `long double` are not supported. For example,

      mpq_class q (99);
      mpq_class q (1.75);
      mpq_class q (1, 3);

Function: `explicit` mpq_class::mpq_class `(const mpq_t q)` ¶

  Construct an `mpq_class` from an `mpq_t`. The value in q is copied into the new `mpq_class`, there won’t be any permanent association between it and q.

Function: `explicit` mpq_class::mpq_class `(const char *s, int base = 0)` ¶
Function: `explicit` mpq_class::mpq_class `(const string& s, int base = 0)` ¶

  Construct an `mpq_class` converted from a string using `mpq_set_str` (see Initialization and Assignment Functions).

  If the string is not a valid rational, an `std::invalid_argument` exception is thrown. The same applies to `operator=`.

Function: `mpq_class` operator"" `_mpq (const char *str)` ¶

  With C++11 compilers, integral rationals can be constructed with the syntax `123_mpq` which is equivalent to `mpq_class(123_mpz)`. Other rationals can be built as `-1_mpq/2` or `0xb_mpq/123456_mpz`.

Function: `void` mpq_class::canonicalize `()` ¶

  Put an `mpq_class` into canonical form, as per Rational Number Functions. All arithmetic operators require their operands in canonical form, and will return results in canonical form.

Function: `mpq_class` abs `(mpq_class op)` ¶
Function: `int` cmp `(mpq_class op1, type op2)` ¶
Function: `int` cmp `(type op1, mpq_class op2)` ¶
Function: `double` mpq_class::get_d `(void)` ¶
Function: `string` mpq_class::get_str `(int base = 10)` ¶
Function: `int` mpq_class::set_str `(const char *str, int base)` ¶
Function: `int` mpq_class::set_str `(const string& str, int base)` ¶
Function: `int` sgn `(mpq_class op)` ¶
Function: `void` mpq_class::swap `(mpq_class& op)` ¶
Function: `void` swap `(mpq_class& op1, mpq_class& op2)` ¶

  These functions provide a C++ class interface to the corresponding GMP C routines.

  `cmp` can be used with any of the classes or the standard C++ types, except `long long` and `long double`.

Function: `mpz_class&` mpq_class::get_num `()` ¶
Function: `mpz_class&` mpq_class::get_den `()` ¶

  Get a reference to an `mpz_class` which is the numerator or denominator of an `mpq_class`. This can be used both for read and write access. If the object returned is modified, it modifies the original `mpq_class`.

  If direct manipulation might produce a non-canonical value, then `mpq_class::canonicalize` must be called before further operations.

Function: `mpz_t` mpq_class::get_num_mpz_t `()` ¶
Function: `mpz_t` mpq_class::get_den_mpz_t `()` ¶

  Get a reference to the underlying `mpz_t` numerator or denominator of an `mpq_class`. This can be passed to C functions expecting an `mpz_t`. Any modifications made to the `mpz_t` will modify the original `mpq_class`.

  If direct manipulation might produce a non-canonical value, then `mpq_class::canonicalize` must be called before further operations.

Function: `istream&` operator>> `(istream& stream, mpq_class& rop);` ¶

  Read rop from stream, using its `ios` formatting settings, the same as `mpq_t operator>>` (see C++ Formatted Input).

  If the rop read might not be in canonical form then `mpq_class::canonicalize` must be called.