fmpz_poly_q.h – rational functions over the rational numbers

Description.

Types, macros and constants

fmpz_poly_q_struct
fmpz_poly_q_t

Description.

Memory management

We represent a rational function over \(\mathbf{Q}\) as the quotient of two coprime integer polynomials of type fmpz_poly_t, enforcing that the leading coefficient of the denominator is positive. The zero function is represented as \(0/1\).

void fmpz_poly_q_init(fmpz_poly_q_t rop)

Initialises rop.

void fmpz_poly_q_clear(fmpz_poly_q_t rop)

Clears the object rop.

fmpz_poly_struct * fmpz_poly_q_numref(const fmpz_poly_q_t op)

Returns a reference to the numerator of op.

fmpz_poly_struct * fmpz_poly_q_denref(const fmpz_poly_q_t op)

Returns a reference to the denominator of op.

void fmpz_poly_q_canonicalise(fmpz_poly_q_t rop)

Brings rop into canonical form, only assuming that the denominator is non-zero.

int fmpz_poly_q_is_canonical(const fmpz_poly_q_t op)

Checks whether the rational function op is in canonical form.

Randomisation

void fmpz_poly_q_randtest(fmpz_poly_q_t poly, flint_rand_t state, slong len1, flint_bitcnt_t bits1, slong len2, flint_bitcnt_t bits2)

Sets poly to a random rational function.

void fmpz_poly_q_randtest_not_zero(fmpz_poly_q_t poly, flint_rand_t state, slong len1, flint_bitcnt_t bits1, slong len2, flint_bitcnt_t bits2)

Sets poly to a random non-zero rational function.

Assignment

void fmpz_poly_q_set(fmpz_poly_q_t rop, const fmpz_poly_q_t op)

Sets the element rop to the same value as the element op.

void fmpz_poly_q_set_si(fmpz_poly_q_t rop, slong op)

Sets the element rop to the value given by the slong op.

void fmpz_poly_q_swap(fmpz_poly_q_t op1, fmpz_poly_q_t op2)

Swaps the elements op1 and op2.

This is done efficiently by swapping pointers.

void fmpz_poly_q_zero(fmpz_poly_q_t rop)

Sets rop to zero.

void fmpz_poly_q_one(fmpz_poly_q_t rop)

Sets rop to one.

void fmpz_poly_q_neg(fmpz_poly_q_t rop, const fmpz_poly_q_t op)

Sets the element rop to the additive inverse of op.

void fmpz_poly_q_inv(fmpz_poly_q_t rop, const fmpz_poly_q_t op)

Sets the element rop to the multiplicative inverse of op.

Assumes that the element op is non-zero.

Comparison

int fmpz_poly_q_is_zero(const fmpz_poly_q_t op)

Returns whether the element op is zero.

int fmpz_poly_q_is_one(const fmpz_poly_q_t op)

Returns whether the element rop is equal to the constant polynomial \(1\).

int fmpz_poly_q_equal(const fmpz_poly_q_t op1, const fmpz_poly_q_t op2)

Returns whether the two elements op1 and op2 are equal.

Addition and subtraction

void fmpz_poly_q_add(fmpz_poly_q_t rop, const fmpz_poly_q_t op1, const fmpz_poly_q_t op2)

Sets rop to the sum of op1 and op2.

void fmpz_poly_q_sub(fmpz_poly_q_t rop, const fmpz_poly_q_t op1, const fmpz_poly_q_t op2)

Sets rop to the difference of op1 and op2.

void fmpz_poly_q_addmul(fmpz_poly_q_t rop, const fmpz_poly_q_t op1, const fmpz_poly_q_t op2)

Adds the product of op1 and op2 to rop.

void fmpz_poly_q_submul(fmpz_poly_q_t rop, const fmpz_poly_q_t op1, const fmpz_poly_q_t op2)

Subtracts the product of op1 and op2 from rop.

Scalar multiplication and division

void fmpz_poly_q_scalar_mul_si(fmpz_poly_q_t rop, const fmpz_poly_q_t op, slong x)

Sets rop to the product of the rational function op and the slong integer \(x\).

void fmpz_poly_q_scalar_mul_mpz(fmpz_poly_q_t rop, const fmpz_poly_q_t op, const mpz_t x)

Sets rop to the product of the rational function op and the mpz_t integer \(x\).

void fmpz_poly_q_scalar_mul_mpq(fmpz_poly_q_t rop, const fmpz_poly_q_t op, const mpq_t x)

Sets rop to the product of the rational function op and the mpq_t rational \(x\).

void fmpz_poly_q_scalar_div_si(fmpz_poly_q_t rop, const fmpz_poly_q_t op, slong x)

Sets rop to the quotient of the rational function op and the slong integer \(x\).

void fmpz_poly_q_scalar_div_mpz(fmpz_poly_q_t rop, const fmpz_poly_q_t op, const mpz_t x)

Sets rop to the quotient of the rational function op and the mpz_t integer \(x\).

void fmpz_poly_q_scalar_div_mpq(fmpz_poly_q_t rop, const fmpz_poly_q_t op, const mpq_t x)

Sets rop to the quotient of the rational function op and the mpq_t rational \(x\).

Multiplication and division

void fmpz_poly_q_mul(fmpz_poly_q_t rop, const fmpz_poly_q_t op1, const fmpz_poly_q_t op2)

Sets rop to the product of op1 and op2.

void fmpz_poly_q_div(fmpz_poly_q_t rop, const fmpz_poly_q_t op1, const fmpz_poly_q_t op2)

Sets rop to the quotient of op1 and op2.

Powering

void fmpz_poly_q_pow(fmpz_poly_q_t rop, const fmpz_poly_q_t op, ulong exp)

Sets rop to the exp-th power of op.

The corner case of exp == 0 is handled by setting rop to the constant function \(1\). Note that this includes the case \(0^0 = 1\).

Derivative

void fmpz_poly_q_derivative(fmpz_poly_q_t rop, const fmpz_poly_q_t op)

Sets rop to the derivative of op.

Evaluation

int fmpz_poly_q_evaluate(mpq_t rop, const fmpz_poly_q_t f, const mpq_t a)

Sets rop to \(f\) evaluated at the rational \(a\).

If the denominator evaluates to zero at \(a\), returns non-zero and does not modify any of the variables. Otherwise, returns \(0\) and sets rop to the rational \(f(a)\).

Input and output

The following three methods enable users to construct elements of type\ fmpz_poly_q_t from strings or to obtain string representations of such elements. The format used is based on the FLINT format for integer polynomials of type fmpz_poly_t, which we recall first: A non-zero polynomial \(a_0 + a_1 X + \dotsb + a_n X^n\) of length \(n + 1\) is represented by the string "n+1  a_0 a_1 ... a_n", where there are two space characters following the length and single space characters separating the individual coefficients. There is no leading or trailing white-space. The zero polynomial is simply represented by "0". We adapt this notation for rational functions as follows. We denote the zero function by "0". Given a non-zero function with numerator and denominator string representations num and den, respectively, we use the string num/den to represent the rational function, unless the denominator is equal to one, in which case we simply use num. There is also a _pretty variant available, which bases the string parts for the numerator and denominator on the output of the function fmpz_poly_get_str_pretty and introduces parentheses where necessary. Note that currently these functions are not optimised for performance and are intended to be used only for debugging purposes or one-off input and output, rather than as a low-level parser.

int fmpz_poly_q_set_str(fmpz_poly_q_t rop, const char *s)

Sets rop to the rational function given by the string s.

char * fmpz_poly_q_get_str(const fmpz_poly_q_t op)

Returns the string representation of the rational function op.

char * fmpz_poly_q_get_str_pretty(const fmpz_poly_q_t op, const char *x)

Returns the pretty string representation of the rational function op.

int fmpz_poly_q_print(const fmpz_poly_q_t op)

Prints the representation of the rational function op to stdout.

int fmpz_poly_q_print_pretty(const fmpz_poly_q_t op, const char *x)

Prints the pretty representation of the rational function op to stdout.