intfuncs.jl

## integer functions ##

isodd(n::Integer) = bool(rem(n,2))
iseven(n::Integer) = !isodd(n)

sign{T<:Integer}(x::T) = convert(T,(x>0)-(x<0))
sign{T<:Unsigned}(x::T) = convert(T,(x>0))

signbit(x::Unsigned) = 0
signbit(x::Int8) = int(x>>>7)
signbit(x::Int16) = int(x>>>15)
signbit(x::Int32) = int(x>>>31)
signbit(x::Int64) = int(x>>>63)
signbit(x::Int128) = int(x>>>127)

flipsign(x::Int32,  y::Int32)  = box(Int32,flipsign_int(unbox(Int32,x),unbox(Int32,y)))
flipsign(x::Int64,  y::Int64)  = box(Int64,flipsign_int(unbox(Int64,x),unbox(Int64,y)))
flipsign(x::Int128, y::Int128) = box(Int128,flipsign_int(unbox(Int128,x),unbox(Int128,y)))

flipsign{T<:Signed}(x::T,y::T)  = flipsign(int(x),int(y))
flipsign(x::Signed, y::Signed)  = flipsign(promote(x,y)...)
flipsign(x::Signed, y::Float32) = flipsign(x, reinterpret(Int32,y))
flipsign(x::Signed, y::Float64) = flipsign(x, reinterpret(Int64,y))
flipsign(x::Signed, y::Real)    = flipsign(x, -oftype(x,signbit(y)))

copysign(x::Signed, y::Signed)  = flipsign(x, x$y)
copysign(x::Signed, y::Float32) = copysign(x, reinterpret(Int32,y))
copysign(x::Signed, y::Float64) = copysign(x, reinterpret(Int64,y))
copysign(x::Signed, y::Real)    = copysign(x, -oftype(x,signbit(y)))

abs(x::Unsigned) = x
abs(x::Signed) = flipsign(x,x)

## number-theoretic functions ##

function gcd{T<:Integer}(a::T, b::T)
    neg = a < 0
    while b != 0
        t = b
        b = rem(a, b)
        a = t
    end
    g = abs(a)
    neg ? -g : g
end
lcm{T<:Integer}(a::T, b::T) = div(a*b, gcd(b,a))

gcd(a::Integer) = a
lcm(a::Integer) = a
gcd(a::Integer, b::Integer) = gcd(promote(a,b)...)
lcm(a::Integer, b::Integer) = lcm(promote(a,b)...)
gcd(a::Integer, b::Integer...) = gcd(a, gcd(b...))
lcm(a::Integer, b::Integer...) = lcm(a, lcm(b...))

# return (gcd(a,b),x,y) such that ax+by == gcd(a,b)
function gcdx(a, b)
    if b == 0
        (a, 1, 0)
    else
        m = rem(a, b)
        k = div((a-m), b)
        (g, x, y) = gcdx(b, m)
        (g, y, x-k*y)
    end
end

# multiplicative inverse of x mod m, error if none
function invmod(n, m)
    g, x, y = gcdx(n, m)
    g != 1 ? error("no inverse exists") : (x < 0 ? m + x : x)
end

# ^ for any x supporting *
function power_by_squaring(x, p::Integer)
    if p == 1
        return x
    elseif p == 0
        return one(x)
    elseif p < 0
        throw(DomainError())
    elseif p == 2
        return x*x
    end
    t = 1
    while t <= p
        t *= 2
    end
    t = div(t,2)
    p -= t
    a = x
    while true
        t = div(t,2)
        if t > 0
            x = x*x
        else
            break
        end

        if p >= t
            x = x*a
            p -= t
        end
    end
    return x
end

^{T<:Integer}(x::T, p::T) = power_by_squaring(x,p)
^(x::Number, p::Integer)  = power_by_squaring(x,p)
^(x, p::Integer)          = power_by_squaring(x,p)

# x^p mod m
function powermod(x::Integer, p::Integer, m::Integer)
    if p == 0
        return one(x)
    elseif p < 0
        throw(DomainError())
    end
    t = 1
    while t <= p
        t *= 2
    end
    t = div(t,2)
    r = 1
    while true
        if p >= t
            r = mod(r*x, m)
            p -= t
        end
        t = div(t,2)
        if t > 0
            r = mod(r*r, m)
        else
            break
        end
    end
    return r
end

# smallest power of 2 >= x
nextpow2(x::Unsigned) = one(x)<<((sizeof(x)<<3)-leading_zeros(x-1))
nextpow2(x::Integer) = oftype(x,x < 0 ? -nextpow2(unsigned(-x)) : nextpow2(unsigned(x)))

ispow2(x::Integer) = (x&(x-1))==0

# smallest integer n for which a^n >= x
function nextpow(a, x)
    n = iceil(log(x) ./ log(a))
    return n - int(a.^(n-1) .>= x) # guard against roundoff error, e.g., with a=5 and x=125
end
# largest integer n for which a^n <= x
function prevpow(a, x)
    n = ifloor(log(x) ./ log(a))
    return n + int(a.^(n+1) .<= x)
end


# decimal digits in an unsigned integer
global const _jl_powers_of_ten = [
    0x0000000000000001, 0x000000000000000a, 0x0000000000000064, 0x00000000000003e8,
    0x0000000000002710, 0x00000000000186a0, 0x00000000000f4240, 0x0000000000989680,
    0x0000000005f5e100, 0x000000003b9aca00, 0x00000002540be400, 0x000000174876e800,
    0x000000e8d4a51000, 0x000009184e72a000, 0x00005af3107a4000, 0x00038d7ea4c68000,
    0x002386f26fc10000, 0x016345785d8a0000, 0x0de0b6b3a7640000, 0x8ac7230489e80000,
]
function ndigits0z(x::Union(Uint8,Uint16,Uint32,Uint64))
    lz = (sizeof(x)<<3)-leading_zeros(x)
    nd = (1233*lz)>>12+1
    nd -= x < _jl_powers_of_ten[nd]
end
function ndigits0z(x::Uint128)
    n = 0
    while x > 0x8ac7230489e80000
        x = div(x,0x8ac7230489e80000)
        n += 19
    end
    return n + ndigits0z(uint64(x))
end
ndigits0z(x::Integer) = ndigits0z(unsigned(abs(x)))

if WORD_SIZE == 32
const _jl_ndigits_max_mul = 69000000
else
const _jl_ndigits_max_mul = 290000000000000000
end

function ndigits0z(n::Unsigned, b::Integer)
    if b == 2  return (sizeof(n)<<3-leading_zeros(n)); end
    if b == 8  return div((sizeof(n)<<3)-leading_zeros(n)+2,3); end
    if b == 16 return (sizeof(n)<<1)-(leading_zeros(n)>>2); end
    if b == 10 return ndigits0z(n); end
    nd = 1
    if n <= _jl_ndigits_max_mul
        # multiplication method is faster, but doesn't work for extreme values
        d = b
        while n >= d
            nd += 1
            d *= b
        end
    else
        while true
            n = div(n, b)
            if n == 0
                break
            end
            nd += 1
        end
    end
    return nd
end
ndigits0z(x::Integer, b::Integer) = ndigits0z(unsigned(abs(x)),b)

ndigits(x::Unsigned, b::Integer) = x==0 ? 1 : ndigits0z(x,b)
ndigits(x::Unsigned)             = x==0 ? 1 : ndigits0z(x)

ndigits(x::Integer, b::Integer) = ndigits(unsigned(abs(x)),b)
ndigits(x::Integer) = ndigits(unsigned(abs(x)))

## integer to string functions ##

const _jl_dig_syms = uint8(['0':'9','a':'z','A':'Z'])

function bin(x::Unsigned, pad::Int, neg::Bool)
    i = neg + max(pad,sizeof(x)<<3-leading_zeros(x))
    a = Array(Uint8,i)
    while i > neg
        a[i] = '0'+(x&0x1)
        x >>= 1
        i -= 1
    end
    if neg; a[1]='-'; end
    ASCIIString(a)
end

function oct(x::Unsigned, pad::Int, neg::Bool)
    i = neg + max(pad,div((sizeof(x)<<3)-leading_zeros(x)+2,3))
    a = Array(Uint8,i)
    while i > neg
        a[i] = '0'+(x&0x7)
        x >>= 3
        i -= 1
    end
    if neg; a[1]='-'; end
    ASCIIString(a)
end

function dec(x::Unsigned, pad::Int, neg::Bool)
    i = neg + max(pad,ndigits0z(x))
    a = Array(Uint8,i)
    while i > neg
        a[i] = '0'+rem(x,10)
        x = div(x,10)
        i -= 1
    end
    if neg; a[1]='-'; end
    ASCIIString(a)
end

function hex(x::Unsigned, pad::Int, neg::Bool)
    i = neg + max(pad,(sizeof(x)<<1)-(leading_zeros(x)>>2))
    a = Array(Uint8,i)
    while i > neg
        a[i] = _jl_dig_syms[(x&0xf)+1]
        x >>= 4
        i -= 1
    end
    if neg; a[1]='-'; end
    ASCIIString(a)
end

function base(symbols::Array{Uint8}, b::Int, x::Unsigned, pad::Int, neg::Bool)
    if !(2 <= b <= length(symbols)) error("invalid base: $b") end
    i = neg + max(pad,ndigits0z(x,b))
    a = Array(Uint8,i)
    while i > neg
        a[i] = symbols[rem(x,b)+1]
        x = div(x,b)
        i -= 1
    end
    if neg; a[1]='-'; end
    ASCIIString(a)
end
base(b::Int, x::Unsigned, p::Int, n::Bool)            = base(_jl_dig_syms, b, x, p, n)
base(s::Array{Uint8}, x::Unsigned, p::Int, n::Bool)   = base(s, length(s), x, p, n)
base(b::Union(Int,Array{Uint8}), x::Unsigned, p::Int) = base(b,x,p,false)
base(b::Union(Int,Array{Uint8}), x::Unsigned)         = base(b,x,1,false)
base(b::Union(Int,Array{Uint8}), x::Integer, p::Int)  = base(b,unsigned(abs(x)),p,x<0)
base(b::Union(Int,Array{Uint8}), x::Integer)          = base(b,unsigned(abs(x)),1,x<0)

for sym in (:bin, :oct, :dec, :hex)
    @eval begin
        ($sym)(x::Unsigned, p::Int) = ($sym)(x,p,false)
        ($sym)(x::Unsigned)         = ($sym)(x,1,false)
        ($sym)(x::Integer, p::Int)  = ($sym)(unsigned(abs(x)),p,x<0)
        ($sym)(x::Integer)          = ($sym)(unsigned(abs(x)),1,x<0)
    end
end

bits(x::Union(Bool,Int8,Uint8))           = bin(reinterpret(Uint8,x),8)
bits(x::Union(Int16,Uint16))              = bin(reinterpret(Uint16,x),16)
bits(x::Union(Char,Int32,Uint32,Float32)) = bin(reinterpret(Uint32,x),32)
bits(x::Union(Int64,Uint64,Float64))      = bin(reinterpret(Uint64,x),64)
bits(x::Union(Int128,Uint128))            = bin(reinterpret(Uint128,x),128)

const PRIMES = [
    2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71,
    73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151,
    157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233,
    239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317,
    331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419,
    421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503,
    509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607,
    613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701,
    709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811,
    821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911,
    919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997, 1009, 1013,
    1019, 1021, 1031, 1033, 1039, 1049, 1051, 1061, 1063, 1069, 1087, 1091,
    1093, 1097, 1103, 1109, 1117, 1123, 1129, 1151, 1153, 1163, 1171, 1181,
    1187, 1193, 1201, 1213, 1217, 1223, 1229, 1231, 1237, 1249, 1259, 1277,
    1279, 1283, 1289, 1291, 1297, 1301, 1303, 1307, 1319, 1321, 1327, 1361,
    1367, 1373, 1381, 1399, 1409, 1423, 1427, 1429, 1433, 1439, 1447, 1451,
    1453, 1459, 1471, 1481, 1483, 1487, 1489, 1493, 1499, 1511, 1523, 1531,
    1543, 1549, 1553, 1559, 1567, 1571, 1579, 1583, 1597, 1601, 1607, 1609,
    1613, 1619, 1621, 1627, 1637, 1657, 1663, 1667, 1669, 1693, 1697, 1699,
    1709, 1721, 1723, 1733, 1741, 1747, 1753, 1759, 1777, 1783, 1787, 1789,
    1801, 1811, 1823, 1831, 1847, 1861, 1867, 1871, 1873, 1877, 1879, 1889,
    1901, 1907, 1913, 1931, 1933, 1949, 1951, 1973, 1979, 1987, 1993, 1997,
    1999, 2003, 2011, 2017, 2027, 2029, 2039, 2053, 2063, 2069, 2081, 2083,
    2087, 2089, 2099, 2111, 2113, 2129, 2131, 2137, 2141, 2143, 2153, 2161,
    2179, 2203, 2207, 2213, 2221, 2237, 2239, 2243, 2251, 2267, 2269, 2273,
    2281, 2287, 2293, 2297, 2309, 2311, 2333, 2339, 2341, 2347, 2351, 2357,
    2371, 2377, 2381, 2383, 2389, 2393, 2399, 2411, 2417, 2423, 2437, 2441,
    2447, 2459, 2467, 2473, 2477, 2503, 2521, 2531, 2539, 2543, 2549, 2551,
    2557, 2579, 2591, 2593, 2609, 2617, 2621, 2633, 2647, 2657, 2659, 2663,
    2671, 2677, 2683, 2687, 2689, 2693, 2699, 2707, 2711, 2713, 2719, 2729,
    2731, 2741, 2749, 2753, 2767, 2777, 2789, 2791, 2797, 2801, 2803, 2819,
    2833, 2837, 2843, 2851, 2857, 2861, 2879, 2887, 2897, 2903, 2909, 2917,
    2927, 2939, 2953, 2957, 2963, 2969, 2971, 2999, 3001, 3011, 3019, 3023,
    3037, 3041, 3049, 3061, 3067, 3079, 3083, 3089, 3109, 3119, 3121, 3137,
    3163, 3167, 3169, 3181, 3187, 3191, 3203, 3209, 3217, 3221, 3229, 3251,
    3253, 3257, 3259, 3271, 3299, 3301, 3307, 3313, 3319, 3323, 3329, 3331,
    3343, 3347, 3359, 3361, 3371, 3373, 3389, 3391, 3407, 3413, 3433, 3449,
    3457, 3461, 3463, 3467, 3469, 3491, 3499, 3511, 3517, 3527, 3529, 3533,
    3539, 3541, 3547, 3557, 3559, 3571, 3581, 3583, 3593, 3607, 3613, 3617,
    3623, 3631, 3637, 3643, 3659, 3671, 3673, 3677, 3691, 3697, 3701, 3709,
    3719, 3727, 3733, 3739, 3761, 3767, 3769, 3779, 3793, 3797, 3803, 3821,
    3823, 3833, 3847, 3851, 3853, 3863, 3877, 3881, 3889, 3907, 3911, 3917,
    3919, 3923, 3929, 3931, 3943, 3947, 3967, 3989, 4001, 4003, 4007, 4013,
    4019, 4021, 4027, 4049, 4051, 4057, 4073, 4079, 4091, 4093, 4099, 4111,
    4127, 4129, 4133, 4139, 4153, 4157, 4159, 4177, 4201, 4211, 4217, 4219,
    4229, 4231, 4241, 4243, 4253, 4259, 4261, 4271, 4273, 4283, 4289, 4297,
    4327, 4337, 4339, 4349, 4357, 4363, 4373, 4391, 4397, 4409, 4421, 4423,
    4441, 4447, 4451, 4457, 4463, 4481, 4483, 4493, 4507, 4513, 4517, 4519,
    4523, 4547, 4549, 4561, 4567, 4583, 4591, 4597, 4603, 4621, 4637, 4639,
    4643, 4649, 4651, 4657, 4663, 4673, 4679, 4691, 4703, 4721, 4723, 4729,
    4733, 4751, 4759, 4783, 4787, 4789, 4793, 4799, 4801, 4813, 4817, 4831,
    4861, 4871, 4877, 4889, 4903, 4909, 4919, 4931, 4933, 4937, 4943, 4951,
    4957, 4967, 4969, 4973, 4987, 4993, 4999, 5003, 5009, 5011, 5021, 5023,
    5039, 5051, 5059, 5077, 5081, 5087, 5099, 5101, 5107, 5113, 5119, 5147,
    5153, 5167, 5171, 5179, 5189, 5197, 5209, 5227, 5231, 5233, 5237, 5261,
    5273, 5279, 5281, 5297, 5303, 5309, 5323, 5333, 5347, 5351, 5381, 5387,
    5393, 5399, 5407, 5413, 5417, 5419, 5431, 5437, 5441, 5443, 5449, 5471,
    5477, 5479, 5483, 5501, 5503, 5507, 5519, 5521, 5527, 5531, 5557, 5563,
    5569, 5573, 5581, 5591, 5623, 5639, 5641, 5647, 5651, 5653, 5657, 5659,
    5669, 5683, 5689, 5693, 5701, 5711, 5717, 5737, 5741, 5743, 5749, 5779,
    5783, 5791, 5801, 5807, 5813, 5821, 5827, 5839, 5843, 5849, 5851, 5857,
    5861, 5867, 5869, 5879, 5881, 5897, 5903, 5923, 5927, 5939, 5953, 5981,
    5987, 6007, 6011, 6029, 6037, 6043, 6047, 6053, 6067, 6073, 6079, 6089,
    6091, 6101, 6113, 6121, 6131, 6133, 6143, 6151, 6163, 6173, 6197, 6199,
    6203, 6211, 6217, 6221, 6229, 6247, 6257, 6263, 6269, 6271, 6277, 6287,
    6299, 6301, 6311, 6317, 6323, 6329, 6337, 6343, 6353, 6359, 6361, 6367,
    6373, 6379, 6389, 6397, 6421, 6427, 6449, 6451, 6469, 6473, 6481, 6491,
    6521, 6529, 6547, 6551, 6553, 6563, 6569, 6571, 6577, 6581, 6599, 6607,
    6619, 6637, 6653, 6659, 6661, 6673, 6679, 6689, 6691, 6701, 6703, 6709,
    6719, 6733, 6737, 6761, 6763, 6779, 6781, 6791, 6793, 6803, 6823, 6827,
    6829, 6833, 6841, 6857, 6863, 6869, 6871, 6883, 6899, 6907, 6911, 6917,
    6947, 6949, 6959, 6961, 6967, 6971, 6977, 6983, 6991, 6997, 7001, 7013,
    7019, 7027, 7039, 7043, 7057, 7069, 7079, 7103, 7109, 7121, 7127, 7129,
    7151, 7159, 7177, 7187, 7193, 7207, 7211, 7213, 7219, 7229, 7237, 7243,
    7247, 7253, 7283, 7297, 7307, 7309, 7321, 7331, 7333, 7349, 7351, 7369,
    7393, 7411, 7417, 7433, 7451, 7457, 7459, 7477, 7481, 7487, 7489, 7499,
    7507, 7517, 7523, 7529, 7537, 7541, 7547, 7549, 7559, 7561, 7573, 7577,
    7583, 7589, 7591, 7603, 7607, 7621, 7639, 7643, 7649, 7669, 7673, 7681,
    7687, 7691, 7699, 7703, 7717, 7723, 7727, 7741, 7753, 7757, 7759, 7789,
    7793, 7817, 7823, 7829, 7841, 7853, 7867, 7873, 7877, 7879, 7883, 7901,
    7907, 7919, 7927, 7933, 7937, 7949, 7951, 7963, 7993, 8009, 8011, 8017,
    8039, 8053, 8059, 8069, 8081, 8087, 8089, 8093, 8101, 8111, 8117, 8123,
    8147, 8161, 8167, 8171, 8179, 8191, 8209, 8219, 8221, 8231, 8233, 8237,
    8243, 8263, 8269, 8273, 8287, 8291, 8293, 8297, 8311, 8317, 8329, 8353,
    8363, 8369, 8377, 8387, 8389, 8419, 8423, 8429, 8431, 8443, 8447, 8461,
    8467, 8501, 8513, 8521, 8527, 8537, 8539, 8543, 8563, 8573, 8581, 8597,
    8599, 8609, 8623, 8627, 8629, 8641, 8647, 8663, 8669, 8677, 8681, 8689,
    8693, 8699, 8707, 8713, 8719, 8731, 8737, 8741, 8747, 8753, 8761, 8779,
    8783, 8803, 8807, 8819, 8821, 8831, 8837, 8839, 8849, 8861, 8863, 8867,
    8887, 8893, 8923, 8929, 8933, 8941, 8951, 8963, 8969, 8971, 8999, 9001,
    9007, 9011, 9013, 9029, 9041, 9043, 9049, 9059, 9067, 9091, 9103, 9109,
    9127, 9133, 9137, 9151, 9157, 9161, 9173, 9181, 9187, 9199, 9203, 9209,
    9221, 9227, 9239, 9241, 9257, 9277, 9281, 9283, 9293, 9311, 9319, 9323,
    9337, 9341, 9343, 9349, 9371, 9377, 9391, 9397, 9403, 9413, 9419, 9421,
    9431, 9433, 9437, 9439, 9461, 9463, 9467, 9473, 9479, 9491, 9497, 9511,
    9521, 9533, 9539, 9547, 9551, 9587, 9601, 9613, 9619, 9623, 9629, 9631,
    9643, 9649, 9661, 9677, 9679, 9689, 9697, 9719, 9721, 9733, 9739, 9743,
    9749, 9767, 9769, 9781, 9787, 9791, 9803, 9811, 9817, 9829, 9833, 9839,
    9851, 9857, 9859, 9871, 9883, 9887, 9901, 9907, 9923, 9929, 9931, 9941,
    9949, 9967, 9973 ]

function factor{T<:Integer}(n::T)
    if n <= 0
        error("factor: number to be factored must be positive")
    end
    h = Dict{T,Int}()
    if n == 1 return h end
    local p::T
    s = ifloor(sqrt(n))
    for p in PRIMES
        if p > s
            break
        end
        if n % p == 0
            while n % p == 0
                h[p] = get(h,p,0)+1
                n = div(n,p)
            end
            if n == 1
                return h
            end
            s = ifloor(sqrt(n))
        end
    end
    p = PRIMES[end]+2
    while p <= s
        if n % p == 0
            while n % p == 0
                h[p] = get(h,p,0)+1
                n = div(n,p)
            end
            if n == 1
                return h
            end
            s = ifloor(sqrt(n))
        end
        p += 2
    end
    h[n] = 1
    return h
end

function isprime{T<:Integer}(n::T)
    if n <= 1
        return false
    elseif n == 2
        return true
    elseif n % 2 == 0
        return false
    end
    local p::T
    s = ifloor(sqrt(n))
    for p in PRIMES
        if p > s
            return true
        end
        if n % p == 0
            return false
        end
    end
    p = PRIMES[end]+2
    while p <= s
        if n % p == 0
            return false
        end
        p += 2
    end
    return true
end