simplemath

func Add ¶

func Add(a, b uint) (uint, error)

Add returns the sum of a and b if no numeric overflow occurs, or an error otherwise.

func BitEq32 ¶

func BitEq32(a, b int32) int32

BitEq32 implements the bitwise-equivalence operation, that is, NOT(XOR(a,b)).

func BitEq64 ¶

func BitEq64(a, b int64) int64

BitEq64 implements the bitwise-equivalence operation, that is, NOT(XOR(a,b)).

func Doz32 ¶

func Doz32(a, b int32) int32

Doz32 implements the difference-or-zero function, in a branchless fashion. See `simplemath.DozB64` for details.

func Doz64 ¶

func Doz64(a, b int64) int64

Doz64 implements the difference-or-zero function, in a branchless fashion. See `simplemath.DozB64` for details.

func DozB32 ¶

func DozB32(a, b int32) int32

DozB32 implements the difference-or-zero function. See `simplemath.DozB64` for details.

func DozB64 ¶

func DozB64(a, b int64) int64

DozB64 implements the difference-or-zero function. DozB64(a,b) is a - b if a >= b, and is 0 if a < b.

It is named "saturated subtraction" in The Coolest Way to Generate Combinations paper by Frank Ruskey and Aaron Williams, see 3.3. Implementation in Computer words, page 10.

See also: `simplemath.Doz64`.

func Factorial ¶

func Factorial(n uint) (uint, error)

Factorial returns the factorial of n, or 1 for n=0. Error is reported if numeric overflow occurs.

func Mul ¶

func Mul(a, b uint) (uint, error)

Mul returns the product of a and b, or an error if numeric overflow occurs.

func MulRange ¶

func MulRange(n2, n1 uint) (r uint, err error)

MulRange calculates the product of all integers within the inclusive interval [n1, n2] (or [n2, n1] if n2 < n1).

It returns the product if no numeric overflow occurs. Otherwise, it returns an error, and the partial product calculated before the overflow is stored in 'r'.

func NumComb ¶

func NumComb(n, k uint) (uint, error)

NumComb calculates the number of combinations for the specified k and n. In other words, it calculates the binomial coefficient: C(n,k)=n!/k!(n-k)!.

n: number of elements to combine; n>=k must hold. k: number of elements in a combination.

Error is reported if numeric overflow occurs.