# fmpz_extras.h – extra methods for FLINT integers¶

This module implements a few utility methods for the FLINT multiprecision integer type (fmpz_t). It is mainly intended for internal use.

## Convenience methods¶

void fmpz_add_si(fmpz_t z, const fmpz_t x, slong y)
void fmpz_sub_si(fmpz_t z, const fmpz_t x, slong y)

Sets z to the sum (respectively difference) of x and y.

void fmpz_adiv_q_2exp(fmpz_t z, const fmpz_t x, mp_bitcnt_t exp)

Sets z to $$x / 2^{exp}$$, rounded away from zero.

void fmpz_ui_pow_ui(fmpz_t x, ulong b, ulong e)

Sets x to b raised to the power e.

void fmpz_max(fmpz_t z, const fmpz_t x, const fmpz_t y)
void fmpz_min(fmpz_t z, const fmpz_t x, const fmpz_t y)

Sets z to the maximum (respectively minimum) of x and y.

## Inlined arithmetic¶

The fmpz_t bignum type uses an immediate representation for small integers, specifically when the absolute value is at most $$2^{62}-1$$ (on 64-bit machines) or $$2^{30}-1$$ (on 32-bit machines). The following methods completely inline the case where all operands (and possibly some intermediate values in the calculation) are known to be small. This is faster in code where all values almost certainly will be much smaller than a full word. In particular, these methods are used within Arb for manipulating exponents of floating-point numbers. Inlining slows down the general case, and increases code size, so these methods should not be used gratuitously.

void fmpz_add_inline(fmpz_t z, const fmpz_t x, const fmpz_t y)
void fmpz_add_si_inline(fmpz_t z, const fmpz_t x, slong y)
void fmpz_add_ui_inline(fmpz_t z, const fmpz_t x, ulong y)

Sets z to the sum of x and y.

void fmpz_sub_si_inline(fmpz_t z, const fmpz_t x, slong y)

Sets z to the difference of x and y.

void fmpz_add2_fmpz_si_inline(fmpz_t z, const fmpz_t x, const fmpz_t y, slong c)

Sets z to the sum of x, y, and c.

mp_size_t _fmpz_size(const fmpz_t x)

Returns the number of limbs required to represent x.

slong _fmpz_sub_small(const fmpz_t x, const fmpz_t y)

Computes the difference of x and y and returns the result as an slong. The result is clamped between -WORD_MAX and WORD_MAX, i.e. between $$\pm (2^{63}-1)$$ inclusive on a 64-bit machine.

## Low-level conversions¶

void fmpz_set_mpn_large(fmpz_t z, mp_srcptr src, mp_size_t n, int negative)

Sets z to the integer represented by the n limbs in the array src, or minus this value if negative is 1. Requires $$n \ge 2$$ and that the top limb of src is nonzero. Note that fmpz_set_ui, fmpz_neg_ui can be used for single-limb integers.

void FMPZ_GET_MPN_READONLY(zsign, zn, zptr, ztmp, zv)

Given an fmpz_t zv, this macro sets zptr to a pointer to the limbs of zv, zn to the number of limbs, and zsign to a sign bit (0 if nonnegative, 1 if negative). The variable ztmp must be a single mp_limb_t, which is used as a buffer. If zv is a small value, zv itself contains no limb array that zptr could point to, so the single limb is copied to ztmp and zptr is set to point to ztmp. The case where zv is zero is not handled specially, and zn is set to 1.

void fmpz_lshift_mpn(fmpz_t z, mp_srcptr src, mp_size_t n, int negative, mp_bitcnt_t shift)

Sets z to the integer represented by the n limbs in the array src, or minus this value if negative is 1, shifted left by shift bits. Requires $$n \ge 1$$ and that the top limb of src is nonzero.