api.md

API

C++17, one header, standard library only.

#include "inf.hpp"

int main() {
    inf::integer a = "12345678901234567890";
    inf::integer b = 42;
    std::cout << a * b << "\n";
    std::cout << inf::pow(a, 3) << "\n";
}

The type lives in namespace inf. Named algorithms (schoolbook, karatsuba, ntt, schonhage_strassen, AlgoD, gcd, …) are also in that namespace and are found by ADL.

inf::integer

• Constructors: default (0), const char*, std::string, any integral type, copy/move
• Assignment from the same
• Arithmetic: + - * / % and the compound forms, prefix/postfix ++ --, unary -
• Shifts: << >> <<= >>= with an integral or integer count
• Comparisons: < > <= >= == != against integer or integrals
• Stream << / >>
• Cast to an arithmetic type (may overflow)
• c_str() — decimal std::string
• integer::rand(bits) — uniformly random positive integer with that many bits

Named algorithms

Function	Role
add sub mul	Building-block arithmetic (mul is × a 64-bit scalar)
schoolbook karatsuba ntt schonhage_strassen	Explicit multiply (* dispatches by size)
AlgoD	Returns qr<integer> {q, r}
div mod	Divide / remainder by a 64-bit scalar
abs min max
gcd lcm sqrt pow
modinv modexp	Modular inverse and exponentiation
sieve(lo, hi)	Primes in [lo, hi]
log2	Exact bit length
log10 / size	Decimal digit count
debug	Prints sign and raw limbs

Primality

inf::primality check(8);          // argument kept for API kinship; BPSW does not use it
bool p = check(n);
inf::integer q = inf::prime(64, check);  // 64-bit prime

Hash

std::hash<inf::integer> is specialized (decimal string), so integer can be an unordered_map key.