## Type aliases for convenience ##

typealias AbstractVector{T} AbstractArray{T,1}
typealias AbstractMatrix{T} AbstractArray{T,2}
typealias AbstractVecOrMat{T} Union(AbstractVector{T}, AbstractMatrix{T})

## Basic functions ##

size{T,n}(t::AbstractArray{T,n}, d) = (d>n ? 1 : size(t)[d])
eltype(x) = Any
eltype{T,n}(::AbstractArray{T,n}) = T
eltype{T,n}(::Type{AbstractArray{T,n}}) = T
eltype{T<:AbstractArray}(::Type{T}) = eltype(super(T))
iseltype(x,T) = eltype(x) <: T
elsize{T}(::AbstractArray{T}) = sizeof(T)
isinteger(x::AbstractArray) = all(isinteger,x)
isinteger{T<:Integer,n}(x::AbstractArray{T,n}) = true
isreal(x::AbstractArray) = all(isreal,x)
isreal{T<:Real,n}(x::AbstractArray{T,n}) = true
ndims{T,n}(::AbstractArray{T,n}) = n
ndims{T,n}(::Type{AbstractArray{T,n}}) = n
ndims{T<:AbstractArray}(::Type{T}) = ndims(super(T))
length(t::AbstractArray) = prod(size(t))::Int
endof(a::AbstractArray) = length(a)
first(a::AbstractArray) = a[1]
first(a) = next(a,start(a))[1]
last(a) = a[end]

function stride(a::AbstractArray, i::Integer)
    if i > ndims(a)
        return length(a)
    end
    s = 1
    for n=1:(i-1)
        s *= size(a, n)
    end
    return s
end

strides(a::AbstractArray) = ntuple(ndims(a), i->stride(a,i))::Dims

function isassigned(a::AbstractArray, i::Int...)
    # TODO
    try
        a[i...]
        true
    catch
        false
    end
end

# used to compute "end" for last index
function trailingsize(A, n)
    s = 1
    for i=n:ndims(A)
        s *= size(A,i)
    end
    return s
end

## Bounds checking ##
checkbounds(sz::Int, i::Int) = 1 <= i <= sz || throw(BoundsError())
checkbounds(sz::Int, i::Real) = checkbounds(sz, to_index(i))
checkbounds(sz::Int, I::AbstractVector{Bool}) = length(I) == sz || throw(BoundsError())
checkbounds(sz::Int, r::Range{Int}) = isempty(r) || (minimum(r) >= 1 && maximum(r) <= sz) || throw(BoundsError())
checkbounds{T<:Real}(sz::Int, r::Range{T}) = checkbounds(sz, to_index(r))

function checkbounds{T <: Real}(sz::Int, I::AbstractArray{T})
    for i in I
        checkbounds(sz, i)
    end
end

checkbounds(A::AbstractArray, I::AbstractArray{Bool}) = size(A) == size(I) || throw(BoundsError())

checkbounds(A::AbstractArray, I) = checkbounds(length(A), I)

function checkbounds(A::AbstractMatrix, I::Union(Real,AbstractArray), J::Union(Real,AbstractArray))
    checkbounds(size(A,1), I)
    checkbounds(size(A,2), J)
end

function checkbounds(A::AbstractArray, I::Union(Real,AbstractArray), J::Union(Real,AbstractArray))
    checkbounds(size(A,1), I)
    checkbounds(trailingsize(A,2), J)
end

function checkbounds(A::AbstractArray, I::Union(Real,AbstractArray)...)
    n = length(I)
    if n > 0
        for dim = 1:(n-1)
            checkbounds(size(A,dim), I[dim])
        end
        checkbounds(trailingsize(A,n), I[n])
    end
end

## Bounds-checking without errors ##
in_bounds(l::Int, i::Integer) = 1 <= i <= l
function in_bounds(sz::Dims, I::Int...)
    n = length(I)
    for dim = 1:(n-1)
        1 <= I[dim] <= sz[dim] || return false
    end
    s = sz[n]
    for i = n+1:length(sz)
        s *= sz[i]
    end
    1 <= I[n] <= s
end

## Constructors ##

# default arguments to similar()
similar{T}(a::AbstractArray{T})               = similar(a, T, size(a))
similar   (a::AbstractArray, T)               = similar(a, T, size(a))
similar{T}(a::AbstractArray{T}, dims::Dims)   = similar(a, T, dims)
similar{T}(a::AbstractArray{T}, dims::Int...) = similar(a, T, dims)
similar   (a::AbstractArray, T, dims::Int...) = similar(a, T, dims)

function reshape(a::AbstractArray, dims::Dims)
    if prod(dims) != length(a)
        error("dimensions must be consistent with array size")
    end
    copy!(similar(a, dims), a)
end
reshape(a::AbstractArray, dims::Int...) = reshape(a, dims)

vec(a::AbstractArray) = reshape(a,length(a))
vec(a::AbstractVector) = a

function squeeze(A::AbstractArray, dims)
    d = ()
    for i in 1:ndims(A)
        if in(i,dims)
            if size(A,i) != 1
                error("squeezed dims must all be size 1")
            end
        else
            d = tuple(d..., size(A,i))
        end
    end
    reshape(A, d)
end

function copy!(dest::AbstractArray, src)
    i = 1
    for x in src
        dest[i] = x
        i += 1
    end
    return dest
end

# copy with minimal requirements on src
# if src is not an AbstractArray, moving to the offset might be O(n)
function copy!(dest::AbstractArray, doffs::Integer, src, soffs::Integer=1)
    st = start(src)
    for j = 1:(soffs-1)
        _, st = next(src, st)
    end
    i = doffs
    while !done(src,st)
        val, st = next(src, st)
        dest[i] = val
        i += 1
    end
    return dest
end

# NOTE: this is to avoid ambiguity with the deprecation of
#   copy!(dest::AbstractArray, src, doffs::Integer)
# Remove this when that deprecation is removed.
function copy!(dest::AbstractArray, doffs::Integer, src::Integer)
    dest[doffs] = src
    return dest
end

# this method must be separate from the above since src might not have a length
function copy!(dest::AbstractArray, doffs::Integer, src, soffs::Integer, n::Integer)
    n == 0 && return dest
    st = start(src)
    for j = 1:(soffs-1)
        _, st = next(src, st)
    end
    for i = doffs:(doffs+n-1)
        done(src,st) && throw(BoundsError())
        val, st = next(src, st)
        dest[i] = val
    end
    return dest
end

# if src is an AbstractArray and a source offset is passed, use indexing
function copy!(dest::AbstractArray, doffs::Integer, src::AbstractArray, soffs::Integer, n::Integer=length(src))
    for i = 0:(n-1)
        dest[doffs+i] = src[soffs+i]
    end
    return dest
end

copy(a::AbstractArray) = copy!(similar(a), a)
copy(a::AbstractArray{None}) = a # cannot be assigned into so is immutable

function copy!{R,S}(B::AbstractVecOrMat{R}, ir_dest::Range{Int}, jr_dest::Range{Int}, A::AbstractVecOrMat{S}, ir_src::Range{Int}, jr_src::Range{Int})
    if length(ir_dest) != length(ir_src) || length(jr_dest) != length(jr_src)
        error("source and destination must have same size")
    end
    checkbounds(B, ir_dest, jr_dest)
    checkbounds(A, ir_src, jr_src)
    jdest = first(jr_dest)
    for jsrc in jr_src
        idest = first(ir_dest)
        for isrc in ir_src
            B[idest,jdest] = A[isrc,jsrc]
            idest += step(ir_dest)
        end
        jdest += step(jr_dest)
    end
    return B
end

function copy_transpose!{R,S}(B::AbstractVecOrMat{R}, ir_dest::Range{Int}, jr_dest::Range{Int}, A::AbstractVecOrMat{S}, ir_src::Range{Int}, jr_src::Range{Int})
    if length(ir_dest) != length(jr_src) || length(jr_dest) != length(ir_src)
        error("source and destination must have same size")
    end
    checkbounds(B, ir_dest, jr_dest)
    checkbounds(A, ir_src, jr_src)
    idest = first(ir_dest)
    for jsrc in jr_src
        jdest = first(jr_dest)
        for isrc in ir_src
            B[idest,jdest] = A[isrc,jsrc]
            jdest += step(jr_dest)
        end
        idest += step(ir_dest)
    end
    return B
end

zero{T}(x::AbstractArray{T}) = fill!(similar(x), zero(T))

## iteration support for arrays as ranges ##

start(a::AbstractArray) = 1
next(a::AbstractArray,i) = (a[i],i+1)
done(a::AbstractArray,i) = (i > length(a))
isempty(a::AbstractArray) = (length(a) == 0)

## Conversions ##

for (f,t) in ((:char,   Char),
              (:int,    Int),
              (:int8,   Int8),
              (:int16,  Int16),
              (:int32,  Int32),
              (:int64,  Int64),
              (:int128, Int128),
              (:uint,   Uint),
              (:uint8,  Uint8),
              (:uint16, Uint16),
              (:uint32, Uint32),
              (:uint64, Uint64),
              (:uint128,Uint128))
    @eval begin
        ($f)(x::AbstractArray{$t}) = x
        ($f)(x::AbstractArray{$t}) = x

        function ($f)(x::AbstractArray)
            y = similar(x,$t)
            i = 1
            for e in x
                y[i] = ($f)(e)
                i += 1
            end
            y
        end
    end
end

for (f,t) in ((:integer, Integer),
              (:unsigned, Unsigned))
    @eval begin
        ($f){T<:$t}(x::AbstractArray{T}) = x
        ($f){T<:$t}(x::AbstractArray{T}) = x

        function ($f)(x::AbstractArray)
            y = similar(x,typeof(($f)(one(eltype(x)))))
            i = 1
            for e in x
                y[i] = ($f)(e)
                i += 1
            end
            y
        end
    end
end

big{T<:FloatingPoint,N}(x::AbstractArray{T,N}) = convert(AbstractArray{BigFloat,N}, x)
big{T<:FloatingPoint,N}(x::AbstractArray{Complex{T},N}) = convert(AbstractArray{Complex{BigFloat},N}, x)
big{T<:Integer,N}(x::AbstractArray{T,N}) = convert(AbstractArray{BigInt,N}, x)

bool(x::AbstractArray{Bool}) = x
bool(x::AbstractArray) = copy!(similar(x,Bool), x)

convert{T,N  }(::Type{AbstractArray{T,N}}, A::AbstractArray{T,N}) = A
convert{T,S,N}(::Type{AbstractArray{T,N}}, A::AbstractArray{S,N}) = copy!(similar(A,T), A)
convert{T,S,N}(::Type{AbstractArray{T  }}, A::AbstractArray{S,N}) = convert(AbstractArray{T,N}, A)

convert{T,N}(::Type{Array}, A::AbstractArray{T,N}) = convert(Array{T,N}, A)

for (f,T) in ((:float16,    Float16),
              (:float32,    Float32),
              (:float64,    Float64),
              (:complex64,  Complex64),
              (:complex128, Complex128))
    @eval ($f){S,N}(x::AbstractArray{S,N}) = convert(AbstractArray{$T,N}, x)
end

float{T<:FloatingPoint}(x::AbstractArray{T}) = x
complex{T<:Complex}(x::AbstractArray{T}) = x

float{T<:Integer64}(x::AbstractArray{T}) = convert(AbstractArray{typeof(float(zero(T)))}, x)
complex{T<:Union(Integer64,Float64,Float32,Float16)}(x::AbstractArray{T}) =
    convert(AbstractArray{typeof(complex(zero(T)))}, x)

function float(A::AbstractArray) 
    cnv(x) = convert(FloatingPoint,x)
    map_promote(cnv, A)
end

function complex(A::AbstractArray) 
    cnv(x) = convert(Complex,x)
    map_promote(cnv, A)
end

full(x::AbstractArray) = x

## range conversions ##

for fn in _numeric_conversion_func_names
    @eval begin
        $fn(r::StepRange) = $fn(r.start):$fn(r.step):$fn(last(r))
        $fn(r::UnitRange) = $fn(r.start):$fn(last(r))
    end
end

for fn in (:float,:float16,:float32,:float64)
    @eval begin
        $fn(r::FloatRange) = FloatRange($fn(r.start), $fn(r.step), r.len, $fn(r.divisor))
    end
end

## Unary operators ##

conj{T<:Real}(x::AbstractArray{T}) = x
conj!{T<:Real}(x::AbstractArray{T}) = x

real{T<:Real}(x::AbstractArray{T}) = x
imag{T<:Real}(x::AbstractArray{T}) = zero(x)

+{T<:Number}(x::AbstractArray{T}) = x
*{T<:Number}(x::AbstractArray{T}) = x

## Binary arithmetic operators ##

*(A::Number, B::AbstractArray) = A .* B
*(A::AbstractArray, B::Number) = A .* B

/(A::AbstractArray, B::Number) = A ./ B

\(A::Number, B::AbstractArray) = B ./ A

## Indexing: getindex ##

getindex(t::AbstractArray, i::Real) = error("indexing not defined for ", typeof(t))

# linear indexing with a single multi-dimensional index
function getindex(A::AbstractArray, I::AbstractArray)
    x = similar(A, size(I))
    for i=1:length(I)
        x[i] = A[I[i]]
    end
    return x
end

# index A[:,:,...,i,:,:,...] where "i" is in dimension "d"
# TODO: more optimized special cases
slicedim(A::AbstractArray, d::Integer, i) =
    A[[ n==d ? i : (1:size(A,n)) for n in 1:ndims(A) ]...]

function flipdim(A::AbstractVector, d::Integer)
    d > 0 || error("dimension to flip must be positive")
    d == 1 || return copy(A)
    reverse(A)
end

function flipdim(A::AbstractArray, d::Integer)
    nd = ndims(A)
    sd = d > nd ? 1 : size(A, d)
    if sd == 1 || isempty(A)
        return copy(A)
    end
    B = similar(A)
    nnd = 0
    for i = 1:nd
        nnd += int(size(A,i)==1 || i==d)
    end
    if nnd==nd
        # flip along the only non-singleton dimension
        for i = 1:sd
            B[i] = A[sd+1-i]
        end
        return B
    end
    alli = [ 1:size(B,n) for n in 1:nd ]
    for i = 1:sd
        B[[ n==d ? sd+1-i : alli[n] for n in 1:nd ]...] = slicedim(A, d, i)
    end
    return B
end

flipud(A::AbstractArray) = flipdim(A, 1)
fliplr(A::AbstractArray) = flipdim(A, 2)

circshift(a::AbstractArray, shiftamt::Real) = circshift(a, [integer(shiftamt)])
function circshift{T,N}(a::AbstractArray{T,N}, shiftamts)
    I = ()
    for i=1:N
        s = size(a,i)
        d = i<=length(shiftamts) ? shiftamts[i] : 0
        I = tuple(I..., d==0 ? [1:s] : mod([-d:s-1-d], s).+1)
    end
    a[(I::NTuple{N,Vector{Int}})...]
end

## Indexing: setindex! ##

# 1-d indexing is assumed defined on subtypes
setindex!(t::AbstractArray, x, i::Real) =
    error("setindex! not defined for ",typeof(t))
setindex!(t::AbstractArray, x) = throw(MethodError(setindex!, (t, x)))

## Indexing: handle more indices than dimensions if "extra" indices are 1

# Don't require vector/matrix subclasses to implement more than 1/2 indices,
# respectively, by handling the extra dimensions in AbstractMatrix.

function getindex(A::AbstractVector, i1,i2,i3...)
    if i2*prod(i3) != 1
        throw(BoundsError())
    end
    A[i1]
end
function getindex(A::AbstractMatrix, i1,i2,i3,i4...)
    if i3*prod(i4) != 1
        throw(BoundsError())
    end
    A[i1,i2]
end

function setindex!(A::AbstractVector, x, i1,i2,i3...)
    if i2*prod(i3) != 1
        throw(BoundsError())
    end
    A[i1] = x
end
function setindex!(A::AbstractMatrix, x, i1,i2,i3,i4...)
    if i3*prod(i4) != 1
        throw(BoundsError())
    end
    A[i1,i2] = x
end

## get (getindex with a default value) ##

typealias RangeVecIntList{A<:AbstractVector{Int}} Union((Union(Range, AbstractVector{Int})...), AbstractVector{UnitRange{Int}}, AbstractVector{Range{Int}}, AbstractVector{A})

get(A::AbstractArray, i::Integer, default) = in_bounds(length(A), i) ? A[i] : default
get(A::AbstractArray, I::(), default) = similar(A, typeof(default), 0)
get(A::AbstractArray, I::Dims, default) = in_bounds(size(A), I...) ? A[I...] : default

function get!{T}(X::AbstractArray{T}, A::AbstractArray, I::Union(Range, AbstractVector{Int}), default::T)
    ind = findin(I, 1:length(A))
    X[ind] = A[I[ind]]
    X[1:first(ind)-1] = default
    X[last(ind)+1:length(X)] = default
    X
end

get(A::AbstractArray, I::Range, default) = get!(similar(A, typeof(default), length(I)), A, I, default)

function get!{T}(X::AbstractArray{T}, A::AbstractArray, I::RangeVecIntList, default::T)
    fill!(X, default)
    dst, src = indcopy(size(A), I)
    X[dst...] = A[src...]
    X
end

get(A::AbstractArray, I::RangeVecIntList, default) = get!(similar(A, typeof(default), map(length, I)...), A, I, default)


## Concatenation ##

promote_eltype() = None
promote_eltype(v1, vs...) = promote_type(eltype(v1), promote_eltype(vs...))

#TODO: ERROR CHECK
cat(catdim::Integer) = Array(None, 0)

vcat() = Array(None, 0)
hcat() = Array(None, 0)

## cat: special cases
hcat{T}(X::T...)         = T[ X[j] for i=1, j=1:length(X) ]
hcat{T<:Number}(X::T...) = T[ X[j] for i=1, j=1:length(X) ]
vcat{T}(X::T...)         = T[ X[i] for i=1:length(X) ]
vcat{T<:Number}(X::T...) = T[ X[i] for i=1:length(X) ]

function vcat(X::Number...)
    T = None
    for x in X
        T = promote_type(T,typeof(x))
    end
    hvcat_fill(Array(T,length(X)), X)
end

function hcat(X::Number...)
    T = None
    for x in X
        T = promote_type(T,typeof(x))
    end
    hvcat_fill(Array(T,1,length(X)), X)
end

function hcat{T}(V::AbstractVector{T}...)
    height = length(V[1])
    for j = 2:length(V)
        if length(V[j]) != height; error("vector must have same lengths"); end
    end
    [ V[j][i]::T for i=1:length(V[1]), j=1:length(V) ]
end

function vcat{T}(V::AbstractVector{T}...)
    n = 0
    for Vk in V
        n += length(Vk)
    end
    a = similar(full(V[1]), n)
    pos = 1
    for k=1:length(V)
        Vk = V[k]
        for i=1:length(Vk)
            a[pos] = Vk[i]
            pos += 1
        end
    end
    a
end

function hcat{T}(A::AbstractVecOrMat{T}...)
    nargs = length(A)
    nrows = size(A[1], 1)
    ncols = 0
    dense = true
    for j = 1:nargs
        Aj = A[j]
        dense &= isa(Aj,Array)
        nd = ndims(Aj)
        ncols += (nd==2 ? size(Aj,2) : 1)
        if size(Aj, 1) != nrows; error("number of rows must match"); end
    end
    B = similar(full(A[1]), nrows, ncols)
    pos = 1
    if dense
        for k=1:nargs
            Ak = A[k]
            n = length(Ak)
            copy!(B, pos, Ak, 1, n)
            pos += n
        end
    else
        for k=1:nargs
            Ak = A[k]
            p1 = pos+(isa(Ak,AbstractMatrix) ? size(Ak, 2) : 1)-1
            B[:, pos:p1] = Ak
            pos = p1+1
        end
    end
    return B
end

function vcat{T}(A::AbstractMatrix{T}...)
    nargs = length(A)
    nrows = sum(a->size(a, 1), A)::Int
    ncols = size(A[1], 2)
    for j = 2:nargs
        if size(A[j], 2) != ncols; error("number of columns must match"); end
    end
    B = similar(full(A[1]), nrows, ncols)
    pos = 1
    for k=1:nargs
        Ak = A[k]
        p1 = pos+size(Ak,1)-1
        B[pos:p1, :] = Ak
        pos = p1+1
    end
    return B
end

## cat: general case

function cat(catdim::Integer, X...)
    nargs = length(X)
    dimsX = map((a->isa(a,AbstractArray) ? size(a) : (1,)), X)
    ndimsX = map((a->isa(a,AbstractArray) ? ndims(a) : 1), X)
    d_max = maximum(ndimsX)

    if catdim > d_max + 1
        for i=1:nargs
            if dimsX[1] != dimsX[i]
                error("all inputs must have same dimensions when concatenating along a higher dimension");
            end
        end
    elseif nargs >= 2
        for d=1:d_max
            if d == catdim; continue; end
            len = d <= ndimsX[1] ? dimsX[1][d] : 1
            for i = 2:nargs
                if len != (d <= ndimsX[i] ? dimsX[i][d] : 1)
                    error("mismatch in dimension ", d)
                end
            end
        end
    end

    cat_ranges = [ catdim <= ndimsX[i] ? dimsX[i][catdim] : 1 for i=1:nargs ]

    function compute_dims(d)
        if d == catdim
            if catdim <= d_max
                return sum(cat_ranges)
            else
                return nargs
            end
        else
            if d <= ndimsX[1]
                return dimsX[1][d]
            else
                return 1
            end
        end
    end

    ndimsC = max(catdim, d_max)
    dimsC = ntuple(ndimsC, compute_dims)::(Int...)
    typeC = promote_type(map(x->isa(x,AbstractArray) ? eltype(x) : typeof(x), X)...)
    C = similar(isa(X[1],AbstractArray) ? full(X[1]) : [X[1]], typeC, dimsC)

    range = 1
    for k=1:nargs
        nextrange = range+cat_ranges[k]
        cat_one = [ i != catdim ? (1:dimsC[i]) : (range:nextrange-1) for i=1:ndimsC ]
        C[cat_one...] = X[k]
        range = nextrange
    end
    return C
end

vcat(X...) = cat(1, X...)
hcat(X...) = cat(2, X...)

cat{T}(catdim::Integer, A::AbstractArray{T}...) = cat_t(catdim, T, A...)

cat(catdim::Integer, A::AbstractArray...) =
    cat_t(catdim, promote_eltype(A...), A...)

function cat_t(catdim::Integer, typeC, A::AbstractArray...)
    # ndims of all input arrays should be in [d-1, d]

    nargs = length(A)
    dimsA = map(size, A)
    ndimsA = map(ndims, A)
    d_max = maximum(ndimsA)

    if catdim > d_max + 1
        for i=1:nargs
            if dimsA[1] != dimsA[i]
                error("all inputs must have same dimensions when concatenating along a higher dimension");
            end
        end
    elseif nargs >= 2
        for d=1:d_max
            if d == catdim; continue; end
            len = d <= ndimsA[1] ? dimsA[1][d] : 1
            for i = 2:nargs
                if len != (d <= ndimsA[i] ? dimsA[i][d] : 1)
                    error("mismatch in dimension ", d)
                end
            end
        end
    end

    cat_ranges = [ catdim <= ndimsA[i] ? dimsA[i][catdim] : 1 for i=1:nargs ]

    function compute_dims(d)
        if d == catdim
            if catdim <= d_max
                return sum(cat_ranges)
            else
                return nargs
            end
        else
            if d <= ndimsA[1]
                return dimsA[1][d]
            else
                return 1
            end
        end
    end

    ndimsC = max(catdim, d_max)
    dimsC = ntuple(ndimsC, compute_dims)::(Int...)
    C = similar(full(A[1]), typeC, dimsC)

    range = 1
    for k=1:nargs
        nextrange = range+cat_ranges[k]
        cat_one = [ i != catdim ? (1:dimsC[i]) : (range:nextrange-1) for i=1:ndimsC ]
        C[cat_one...] = A[k]
        range = nextrange
    end
    return C
end

vcat(A::AbstractArray...) = cat(1, A...)
hcat(A::AbstractArray...) = cat(2, A...)

# 2d horizontal and vertical concatenation

function hvcat(nbc::Integer, as...)
    # nbc = # of block columns
    n = length(as)
    if mod(n,nbc) != 0
        error("all rows must have the same number of block columns")
    end
    nbr = div(n,nbc)
    hvcat(ntuple(nbr, i->nbc), as...)
end

function hvcat{T}(rows::(Int...), as::AbstractMatrix{T}...)
    nbr = length(rows)  # number of block rows

    nc = 0
    for i=1:rows[1]
        nc += size(as[i],2)
    end

    nr = 0
    a = 1
    for i = 1:nbr
        nr += size(as[a],1)
        a += rows[i]
    end

    out = similar(full(as[1]), T, nr, nc)

    a = 1
    r = 1
    for i = 1:nbr
        c = 1
        szi = size(as[a],1)
        for j = 1:rows[i]
            Aj = as[a+j-1]
            szj = size(Aj,2)
            if size(Aj,1) != szi
                error("mismatched height in block row ", i)
            end
            if c-1+szj > nc
                error("block row ", i, " has mismatched number of columns")
            end
            out[r:r-1+szi, c:c-1+szj] = Aj
            c += szj
        end
        if c != nc+1
            error("block row ", i, " has mismatched number of columns")
        end
        r += szi
        a += rows[i]
    end
    out
end

hvcat(rows::(Int...)) = []

function hvcat{T<:Number}(rows::(Int...), xs::T...)
    nr = length(rows)
    nc = rows[1]

    a = Array(T, nr, nc)
    if length(a) != length(xs)
        error("argument count does not match specified shape")
    end
    k = 1
    @inbounds for i=1:nr
        if nc != rows[i]
            error("row ", i, " has mismatched number of columns")
        end
        for j=1:nc
            a[i,j] = xs[k]
            k += 1
        end
    end
    a
end

function hvcat_fill(a, xs)
    k = 1
    nr, nc = size(a,1), size(a,2)
    for i=1:nr
        @inbounds for j=1:nc
            a[i,j] = xs[k]
            k += 1
        end
    end
    a
end

function hvcat(rows::(Int...), xs::Number...)
    nr = length(rows)
    nc = rows[1]
    #error check
    for i = 2:nr
        if nc != rows[i]
            error("row ", i, " has mismatched number of columns")
        end
    end
    T = typeof(xs[1])
    for i=2:length(xs)
        T = promote_type(T,typeof(xs[i]))
    end
    if nr*nc != length(xs)
        error("argument count does not match specified shape")
    end
    hvcat_fill(Array(T, nr, nc), xs)
end

## Reductions and scans ##

function isequal(A::AbstractArray, B::AbstractArray)
    if A === B return true end
    if size(A) != size(B)
        return false
    end
    if isa(A,Range) != isa(B,Range)
        return false
    end
    for i = 1:length(A)
        if !isequal(A[i], B[i])
            return false
        end
    end
    return true
end

function lexcmp(A::AbstractArray, B::AbstractArray)
    nA, nB = length(A), length(B)
    for i = 1:min(nA, nB)
        res = lexcmp(A[i], B[i])
        res == 0 || return res
    end
    return cmp(nA, nB)
end

function (==)(A::AbstractArray, B::AbstractArray)
    if size(A) != size(B)
        return false
    end
    if isa(A,Range) != isa(B,Range)
        return false
    end
    for i = 1:length(A)
        if !(A[i]==B[i])
            return false
        end
    end
    return true
end

# Uses K-B-N summation
function cumsum_kbn{T<:FloatingPoint}(v::AbstractVector{T})
    n = length(v)
    r = similar(v, n)
    if n == 0; return r; end

    s = r[1] = v[1]
    c = zero(T)
    for i=2:n
        vi = v[i]
        t = s + vi
        if abs(s) >= abs(vi)
            c += ((s-t) + vi)
        else
            c += ((vi-t) + s)
        end
        s = t
        r[i] = s+c
    end
    return r
end

# Uses K-B-N summation
function cumsum_kbn{T<:FloatingPoint}(A::AbstractArray{T}, axis::Integer)
    dimsA = size(A)
    ndimsA = ndims(A)
    axis_size = dimsA[axis]
    axis_stride = 1
    for i = 1:(axis-1)
        axis_stride *= size(A,i)
    end

    if axis_size <= 1
        return A
    end

    B = similar(A)
    C = similar(A)

    for i = 1:length(A)
        if div(i-1, axis_stride) % axis_size == 0
            B[i] = A[i]
            C[i] = zero(T)
        else
            s = B[i-axis_stride]
            Ai = A[i]
            B[i] = t = s + Ai
            if abs(s) >= abs(Ai)
                C[i] = C[i-axis_stride] + ((s-t) + Ai)
            else
                C[i] = C[i-axis_stride] + ((Ai-t) + s)
            end
        end
    end

    return B + C
end

## ipermutedims in terms of permutedims ##

function ipermutedims(A::AbstractArray,perm)
    iperm = Array(Int,length(perm))
    for i = 1:length(perm)
        iperm[perm[i]] = i
    end
    return permutedims(A,iperm)
end

## Other array functions ##

# fallback definition of hvcat in terms of hcat and vcat
function hvcat(rows::(Int...), as...)
    nbr = length(rows)  # number of block rows
    rs = cell(nbr)
    a = 1
    for i = 1:nbr
        rs[i] = hcat(as[a:a-1+rows[i]]...)
        a += rows[i]
    end
    vcat(rs...)
end

function repmat(a::AbstractVecOrMat, m::Int, n::Int=1)
    o, p = size(a,1), size(a,2)
    b = similar(a, o*m, p*n)
    for j=1:n
        d = (j-1)*p+1
        R = d:d+p-1
        for i=1:m
            c = (i-1)*o+1
            b[c:c+o-1, R] = a
        end
    end
    return b
end

function repmat(a::AbstractVector, m::Int)
    o = length(a)
    b = similar(a, o*m)
    for i=1:m
        c = (i-1)*o+1
        b[c:c+o-1] = a
    end
    return b
end

sub2ind(dims) = 1
sub2ind(dims, i::Integer) = int(i)
sub2ind(dims, i::Integer, j::Integer) = sub2ind(dims, int(i), int(j))
sub2ind(dims, i::Int, j::Int) = (j-1)*dims[1] + i
sub2ind(dims, i0::Integer, i1::Integer, i2::Integer) = sub2ind(dims, int(i0),int(i1),int(i2))
sub2ind(dims, i0::Int, i1::Int, i2::Int) =
    i0 + dims[1]*((i1-1) + dims[2]*(i2-1))
sub2ind(dims, i0::Integer, i1::Integer, i2::Integer, i3::Integer) =
    sub2ind(dims, int(i0),int(i1),int(i2),int(i3))
sub2ind(dims, i0::Int, i1::Int, i2::Int, i3::Int) =
    i0 + dims[1]*((i1-1) + dims[2]*((i2-1) + dims[3]*(i3-1)))

function sub2ind(dims, I::Integer...)
    ndims = length(dims)
    index = int(I[1])
    stride = 1
    for k=2:ndims
        stride = stride * dims[k-1]
        index += (int(I[k])-1) * stride
    end
    return index
end

function sub2ind{T<:Integer}(dims::Array{T}, sub::Array{T})
    ndims = length(dims)
    ind = sub[1]
    stride = 1
    for k in 2:ndims
        stride = stride * dims[k - 1]
        ind += (sub[k] - 1) * stride
    end
    return ind
end

sub2ind{T<:Integer}(dims, I::AbstractVector{T}...) =
    [ sub2ind(dims, map(X->X[i], I)...)::Int for i=1:length(I[1]) ]

function ind2sub(dims::(Integer,Integer...), ind::Int)
    ndims = length(dims)
    stride = dims[1]
    for i=2:ndims-1
        stride *= dims[i]
    end

    sub = ()
    for i=(ndims-1):-1:1
        rest = rem(ind-1, stride) + 1
        sub = tuple(div(ind - rest, stride) + 1, sub...)
        ind = rest
        stride = div(stride, dims[i])
    end
    return tuple(ind, sub...)
end

ind2sub(dims::(Integer...), ind::Integer) = ind2sub(dims, int(ind))
ind2sub(dims::(), ind::Integer) = ind==1 ? () : throw(BoundsError())
ind2sub(dims::(Integer,), ind::Int) = (ind,)
ind2sub(dims::(Integer,Integer), ind::Int) =
    (rem(ind-1,dims[1])+1, div(ind-1,dims[1])+1)
ind2sub(dims::(Integer,Integer,Integer), ind::Int) =
    (rem(ind-1,dims[1])+1, div(rem(ind-1,dims[1]*dims[2]), dims[1])+1,
     div(rem(ind-1,dims[1]*dims[2]*dims[3]), dims[1]*dims[2])+1)

function ind2sub{T<:Integer}(dims::(Integer,Integer...), ind::AbstractVector{T})
    n = length(dims)
    l = length(ind)
    t = ntuple(n, x->Array(Int, l))
    for i = 1:l
        s = ind2sub(dims, ind[i])
        for j = 1:n
            t[j][i] = s[j]
        end
    end
    return t
end

function ind2sub!{T<:Integer}(sub::Array{T}, dims::Array{T}, ind::T)
    ndims = length(dims)
    stride = dims[1]
    for i in 2:(ndims - 1)
        stride *= dims[i]
    end
    for i in (ndims - 1):-1:1
        rest = rem1(ind, stride)
        sub[i + 1] = div(ind - rest, stride) + 1
        ind = rest
        stride = div(stride, dims[i])
    end
    sub[1] = ind
    return
end

# Generalized repmat
function repeat{T}(A::Array{T};
                   inner::Array{Int} = ones(Int, ndims(A)),
                   outer::Array{Int} = ones(Int, ndims(A)))
    ndims_in = ndims(A)
    length_inner = length(inner)
    length_outer = length(outer)
    ndims_out = max(ndims_in, length_inner, length_outer)

    if length_inner < ndims_in || length_outer < ndims_in
        msg = "inner/outer repetitions must be set for all input dimensions"
        throw(ArgumentError(msg))
    end

    size_in = Array(Int, ndims_in)
    size_out = Array(Int, ndims_out)
    inner_size_out = Array(Int, ndims_out)

    for i in 1:ndims_in
        size_in[i] = size(A, i)
    end
    for i in 1:ndims_out
        t1 = ndims_in < i ? 1 : size_in[i]
        t2 = length_inner < i ? 1 : inner[i]
        t3 = length_outer < i ? 1 : outer[i]
        size_out[i] = t1 * t2 * t3
        inner_size_out[i] = t1 * t2
    end

    indices_in = Array(Int, ndims_in)
    indices_out = Array(Int, ndims_out)

    length_out = prod(size_out)
    R = Array(T, size_out...)

    for index_out in 1:length_out
        ind2sub!(indices_out, size_out, index_out)
        for t in 1:ndims_in
            # "Project" outer repetitions into inner repetitions
            indices_in[t] = mod1(indices_out[t], inner_size_out[t])
            # Find inner repetitions using flooring division
            if inner[t] != 1
                indices_in[t] = fld1(indices_in[t], inner[t])
            end
        end
        index_in = sub2ind(size_in, indices_in)
        R[index_out] = A[index_in]
    end

    return R
end

## iteration utilities ##

# slow, but useful
function cartesianmap(body, t::(Int...), it...)
    idx = length(t)-length(it)
    if idx == 1
        for i = 1:t[1]
            body(i, it...)
        end
    elseif idx == 2
        for j = 1:t[2]
            for i = 1:t[1]
                body(i, j, it...)
            end
        end
    elseif idx > 1
        for j = 1:t[idx]
            for i = 1:t[idx-1]
                cartesianmap(body, t, i, j, it...)
            end
        end
    else
        throw(ArgumentError("cartesianmap"))
    end
end

cartesianmap(body, t::()) = (body(); nothing)

function cartesianmap(body, t::(Int,))
    for i = 1:t[1]
        body(i)
    end
end

function cartesianmap(body, t::(Int,Int))
    for j = 1:t[2]
        for i = 1:t[1]
            body(i,j)
        end
    end
end

function cartesianmap(body, t::(Int,Int,Int))
    for k = 1:t[3]
        for j = 1:t[2]
            for i = 1:t[1]
                body(i,j,k)
            end
        end
    end
end

##
# generic map on any iterator
function map(f::Callable, iters...)
    result = {}
    len = length(iters)
    states = [start(iters[idx]) for idx in 1:len]
    nxtvals = cell(len)
    cont = true
    for idx in 1:len
        done(iters[idx], states[idx]) && (cont = false; break)
    end
    while cont
        for idx in 1:len
            nxtvals[idx],states[idx] = next(iters[idx], states[idx])
        end
        push!(result, f(nxtvals...))
        for idx in 1:len
            done(iters[idx], states[idx]) && (cont = false; break)
        end
    end
    result
end

## map over arrays ##

## transform any set of dimensions
## dims specifies which dimensions will be transformed. for example
## dims==1:2 will call f on all slices A[:,:,...]
mapslices(f::Function, A::AbstractArray, dims) = mapslices(f, A, [dims...])
function mapslices(f::Function, A::AbstractArray, dims::AbstractVector)
    if isempty(dims)
        return map(f,A)
    end

    dimsA = [size(A)...]
    ndimsA = ndims(A)
    alldims = [1:ndimsA]

    otherdims = setdiff(alldims, dims)

    idx = cell(ndimsA)
    fill!(idx, 1)
    Asliceshape = tuple(dimsA[dims]...)
    itershape   = tuple(dimsA[otherdims]...)
    for d in dims
        idx[d] = 1:size(A,d)
    end

    r1 = f(reshape(A[idx...], Asliceshape))

    # determine result size and allocate
    Rsize = copy(dimsA)
    # TODO: maybe support removing dimensions
    if !isa(r1, AbstractArray) || ndims(r1) == 0
        r1 = [r1]
    end
    Rsize[dims] = [size(r1)...; ones(Int,max(0,length(dims)-ndims(r1)))]
    R = similar(r1, tuple(Rsize...))

    ridx = cell(ndims(R))
    fill!(ridx, 1)
    for d in dims
        ridx[d] = 1:size(R,d)
    end

    R[ridx...] = r1

    first = true
    cartesianmap(itershape) do idxs...
        if first
            first = false
        else
            ia = [idxs...]
            idx[otherdims] = ia
            ridx[otherdims] = ia
            R[ridx...] = f(reshape(A[idx...], Asliceshape))
        end
    end

    return R
end


# using promote_type
function promote_to!{T}(f::Callable, offs, dest::AbstractArray{T}, A::AbstractArray)
    # map to dest array, checking the type of each result. if a result does not
    # match, do a type promotion and re-dispatch.
    @inbounds for i = offs:length(A)
        el = f(A[i])
        S = typeof(el)
        if S === T || S <: T
            dest[i] = el::T
        else
            R = promote_type(T, S)
            if R !== T
                new = similar(dest, R)
                copy!(new,1, dest,1, i-1)
                new[i] = el
                return promote_to!(f, i+1, new, A)
            end
            dest[i] = el
        end
    end
    return dest
end

function map_promote(f::Callable, A::AbstractArray)
    if isempty(A); return similar(A, None); end
    first = f(A[1])
    dest = similar(A, typeof(first))
    dest[1] = first
    return promote_to!(f, 2, dest, A)
end

## 1 argument
function map_to!{T}(f::Callable, offs, dest::AbstractArray{T}, A::AbstractArray)
    # map to dest array, checking the type of each result. if a result does not
    # match, widen the result type and re-dispatch.
    @inbounds for i = offs:length(A)
        el = f(A[i])
        S = typeof(el)
        if S === T || S <: T
            dest[i] = el::T
        else
            R = typejoin(T, S)
            new = similar(dest, R)
            copy!(new,1, dest,1, i-1)
            new[i] = el
            return map_to!(f, i+1, new, A)
        end
    end
    return dest
end

function map(f::Callable, A::AbstractArray)
    if isempty(A); return similar(A); end
    first = f(A[1])
    dest = similar(A, typeof(first))
    dest[1] = first
    return map_to!(f, 2, dest, A)
end

## 2 argument
function map_to!{T}(f::Callable, offs, dest::AbstractArray{T}, A::AbstractArray, B::AbstractArray)
    @inbounds for i = offs:length(A)
        el = f(A[i], B[i])
        S = typeof(el)
        if (S !== T) && !(S <: T)
            R = typejoin(T, S)
            new = similar(dest, R)
            copy!(new,1, dest,1, i-1)
            new[i] = el
            return map_to!(f, i+1, new, A, B)
        end
        dest[i] = el::T
    end
    return dest
end

function map(f::Callable, A::AbstractArray, B::AbstractArray)
    shp = promote_shape(size(A),size(B))
    if prod(shp) == 0
        return similar(A, promote_type(eltype(A),eltype(B)), shp)
    end
    first = f(A[1], B[1])
    dest = similar(A, typeof(first), shp)
    dest[1] = first
    return map_to!(f, 2, dest, A, B)
end

## N argument
function map_to!{T}(f::Callable, offs, dest::AbstractArray{T}, As::AbstractArray...)
    local i
    ith = a->a[i]
    @inbounds for i = offs:length(As[1])
        el = f(map(ith, As)...)
        S = typeof(el)
        if (S !== T) && !(S <: T)
            R = typejoin(T, S)
            new = similar(dest, R)
            copy!(new,1, dest,1, i-1)
            new[i] = el
            return map_to!(f, i+1, new, As...)
        end
        dest[i] = el::T
    end
    return dest
end

function map(f::Callable, As::AbstractArray...)
    shape = mapreduce(size, promote_shape, As)
    if prod(shape) == 0
        return similar(As[1], promote_eltype(As...), shape)
    end
    first = f(map(a->a[1], As)...)
    dest = similar(As[1], typeof(first), shape)
    dest[1] = first
    return map_to!(f, 2, dest, As...)
end

# multi-item push!, unshift! (built on top of type-specific 1-item version)
# (note: must not cause a dispatch loop when 1-item case is not defined)
push!(A) = A
push!(A, a, b) = push!(push!(A, a), b)
push!(A, a, b, c...) = push!(push!(A, a, b), c...)
unshift!(A) = A
unshift!(A, a, b) = unshift!(unshift!(A, b), a)
unshift!(A, a, b, c...) = unshift!(unshift!(A, c...), a, b)

# Fill S (resized as needed) with a random subsequence of A, where
# each element of A is included in S with independent probability p.
# (Note that this is different from the problem of finding a random
#  size-m subset of A where m is fixed!)
function randsubseq!(S::AbstractArray, A::AbstractArray, p::Real)
    0 <= p <= 1 || throw(ArgumentError("probability $p not in [0,1]"))
    n = length(A)
    p == 1 && return copy!(resize!(S, n), A)
    empty!(S)
    p == 0 && return S
    nexpected = p * length(A)
    sizehint(S, iround(nexpected + 5*sqrt(nexpected)))
    if p > 0.15 # empirical threshold for trivial O(n) algorithm to be better
        for i = 1:n
            rand() <= p && push!(S, A[i])
        end
    else
        # Skip through A, in order, from each element i to the next element i+s
        # included in S. The probability that the next included element is 
        # s==k (k > 0) is (1-p)^(k-1) * p, and hence the probability (CDF) that
        # s is in {1,...,k} is 1-(1-p)^k = F(k).   Thus, we can draw the skip s
        # from this probability distribution via the discrete inverse-transform
        # method: s = iceil(F^{-1}(u)) where u = rand(), which is simply
        # s = iceil(log(rand()) / log1p(-p)).
        L = 1 / log1p(-p)
        i = 0
        while true
            s = log(rand()) * L # note that rand() < 1, so s > 0
            s >= n - i && return S # compare before iceil to avoid overflow
            push!(S, A[i += iceil(s)])
        end
        # [This algorithm is similar in spirit to, but much simpler than,
        #  the one by Vitter for a related problem in "Faster methods for
        #  random sampling," Comm. ACM Magazine 7, 703-718 (1984).]
    end
    return S
end

randsubseq{T}(A::AbstractArray{T}, p::Real) = randsubseq!(T[], A, p)