add impl

Author: oscardssmith

src

@@ -0,0 +1,50 @@
+export iroot, ispower, rootrem find_exponent, is_probably_prime
+
+module IntegerMathUtils
+
+iroot(x::Integer, n::Integer) = iroot(x, Cint(n))
+
+# TODO: Add more efficient implimentation
+iroot(x::T, n::Cint) where {T<:Integer} = T(iroot(big(x), Cint(n)))
+
+function iroot(x::BigInt, n::Cint)
+    n <= 0 && throw(DomainError(n, "Exponent must be > 0"))
+    x <= 0 && iseven(x) && throw(DomainError(n, "This is a math no-no"))
+    ans = BigInt()
+    ccall((:__gmpz_root, :libgmp), Cint, (Ref{BigInt}, Ref{BigInt}, Cint), ans, x, n)
+    ans
+end
+
+# TODO: Add more efficient implimentation for smaller types
+function rootrem(x::T, n::Integer) where {T<:Integer}
+    x = big(x)
+    n = Cint(n)
+    n <= 0 && throw(DomainError(n, "Exponent must be > 0"))
+    x <= 0 && iseven(x) && throw(DomainError(n, "This is a math no-no"))
+    root = BigInt()
+    rem  = BigInt()
+    ccall((:__gmpz_rootrem, :libgmp), Nothing,(Ref{BigInt}, Ref{BigInt}, Ref{BigInt}, Int), root, rem, x, n)
+    return (root, T(rem))
+end
+
+# TODO: Add more efficient implimentation for smaller types
+ispower(x::Integer) = ispower(big(x))
+
+function ispower(x::BigInt)
+    return 0 != ccall((:__gmpz_perfect_power_p, :libgmp), Cint, (Ref{BigInt},), x)
+end
+
+# TODO: Add more efficient implimentation for smaller types
+function find_exponent(x::Integer)
+    x <= 1 && return 1
+    for exponent in ndigits(x, base=2):-1:2
+        rootrem(x, exponent)[2] == 0 && return exponent
+    end
+    1
+end
+
+function is_probably_prime(x::Integer; reps=25)
+    return ccall((:__gmpz_probab_prime_p, :libgmp), Cint, (Ref{BigInt}, Cint), x, reps) != 0
+end
+
+end