# This file is a part of Julia. License is MIT: http://julialang.org/license

module Rounding
include(String(vcat(length(Core.ARGS)>=2?Core.ARGS[2].data:"".data, "fenv_constants.jl".data))) # include($BUILDROOT/base/fenv_constants.jl)

export
    RoundingMode, RoundNearest, RoundToZero, RoundUp, RoundDown, RoundFromZero,
    RoundNearestTiesAway, RoundNearestTiesUp,
    rounding, setrounding,
    get_zero_subnormals, set_zero_subnormals

## rounding modes ##
"""
    RoundingMode

A type used for controlling the rounding mode of floating point operations (via
[`rounding`](:func:`rounding`)/[`setrounding`](:func:`setrounding`) functions), or as
optional arguments for rounding to the nearest integer (via the [`round`](:func:`round`)
function).

Currently supported rounding modes are:

- [`RoundNearest`](:obj:`RoundNearest`) (default)
- [`RoundNearestTiesAway`](:obj:`RoundNearestTiesAway`)
- [`RoundNearestTiesUp`](:obj:`RoundNearestTiesUp`)
- [`RoundToZero`](:obj:`RoundToZero`)
- [`RoundFromZero`](:obj:`RoundFromZero`) (`BigFloat` only)
- [`RoundUp`](:obj:`RoundUp`)
- [`RoundDown`](:obj:`RoundDown`)
"""
immutable RoundingMode{T} end

"""
    RoundNearest

The default rounding mode. Rounds to the nearest integer, with ties (fractional values of
0.5) being rounded to the nearest even integer.
"""
const RoundNearest = RoundingMode{:Nearest}()

"""
    RoundToZero

[`round`](:func:`round`) using this rounding mode is an alias for [`trunc`](:func:`trunc`).
"""
const RoundToZero = RoundingMode{:ToZero}()

"""
    RoundUp

[`round`](:func:`round`) using this rounding mode is an alias for [`ceil`](:func:`ceil`).
"""
const RoundUp = RoundingMode{:Up}()

"""
    RoundDown

[`round`](:func:`round`) using this rounding mode is an alias for [`floor`](:func:`floor`).
"""
const RoundDown = RoundingMode{:Down}()

const RoundFromZero = RoundingMode{:FromZero}() # mpfr only

"""
    RoundNearestTiesAway

Rounds to nearest integer, with ties rounded away from zero (C/C++
[`round`](:func:`round`) behaviour).
"""
const RoundNearestTiesAway = RoundingMode{:NearestTiesAway}()

"""
    RoundNearestTiesUp

Rounds to nearest integer, with ties rounded toward positive infinity (Java/JavaScript
[`round`](:func:`round`) behaviour).
"""
const RoundNearestTiesUp = RoundingMode{:NearestTiesUp}()

to_fenv(::RoundingMode{:Nearest}) = JL_FE_TONEAREST
to_fenv(::RoundingMode{:ToZero}) = JL_FE_TOWARDZERO
to_fenv(::RoundingMode{:Up}) = JL_FE_UPWARD
to_fenv(::RoundingMode{:Down}) = JL_FE_DOWNWARD

function from_fenv(r::Integer)
    if r == JL_FE_TONEAREST
        return RoundNearest
    elseif r == JL_FE_DOWNWARD
        return RoundDown
    elseif r == JL_FE_UPWARD
        return RoundUp
    elseif r == JL_FE_TOWARDZERO
        return RoundToZero
    else
        throw(ArgumentError("invalid rounding mode code: $r"))
    end
end

"""
    setrounding(T, mode)

Set the rounding mode of floating point type `T`, controlling the rounding of basic
arithmetic functions ([`+`](:func:`+`), [`-`](:func:`-`), [`*`](:func:`*`), [`/`](:func:`/`)
and [`sqrt`](:func:`sqrt`)) and type conversion.

Note that this may affect other types, for instance changing the rounding mode of `Float64`
will change the rounding mode of `Float32`. See [`RoundingMode`](:obj:`RoundingMode`) for
available modes.
"""
setrounding(T::Type, mode)

"""
    rounding(T)

Get the current floating point rounding mode for type `T`, controlling the rounding of basic
arithmetic functions ([`+`](:func:`+`), [`-`](:func:`-`), [`*`](:func:`*`), [`/`](:func:`/`)
and [`sqrt`](:func:`sqrt`)) and type conversion.

See [`RoundingMode`](:obj:`RoundingMode`) for available modes.
"""
:rounding

setrounding_raw{T<:Union{Float32,Float64}}(::Type{T},i::Integer) = ccall(:fesetround, Int32, (Int32,), i)
rounding_raw{T<:Union{Float32,Float64}}(::Type{T}) = ccall(:fegetround, Int32, ())

setrounding{T<:Union{Float32,Float64}}(::Type{T},r::RoundingMode) = setrounding_raw(T,to_fenv(r))
rounding{T<:Union{Float32,Float64}}(::Type{T}) = from_fenv(rounding_raw(T))

"""
    setrounding(f::Function, T, mode)

Change the rounding mode of floating point type `T` for the duration of `f`. It is logically
equivalent to:

    old = rounding(T)
    setrounding(T, mode)
    f()
    setrounding(T, old)

See [`RoundingMode`](:obj:`RoundingMode`) for available rounding modes.
"""
function setrounding{T}(f::Function, ::Type{T}, rounding::RoundingMode)
    old_rounding_raw = rounding_raw(T)
    setrounding(T,rounding)
    try
        return f()
    finally
        setrounding_raw(T,old_rounding_raw)
    end
end


# Should be equivalent to:
#   setrounding(Float64,r) do
#       convert(T,x)
#   end
# but explicit checks are currently quicker (~20x).
# Assumes conversion is performed by rounding to nearest value.

# To avoid ambiguous dispatch with methods in mpfr.jl:
(::Type{T}){T<:AbstractFloat}(x::Real,r::RoundingMode) = _convert_rounding(T,x,r)

_convert_rounding{T<:AbstractFloat}(::Type{T},x::Real,r::RoundingMode{:Nearest}) = convert(T,x)
function _convert_rounding{T<:AbstractFloat}(::Type{T},x::Real,r::RoundingMode{:Down})
    y = convert(T,x)
    y > x ? prevfloat(y) : y
end
function _convert_rounding{T<:AbstractFloat}(::Type{T},x::Real,r::RoundingMode{:Up})
    y = convert(T,x)
    y < x ? nextfloat(y) : y
end
function _convert_rounding{T<:AbstractFloat}(::Type{T},x::Real,r::RoundingMode{:ToZero})
    y = convert(T,x)
    if x > 0.0
        y > x ? prevfloat(y) : y
    else
        y < x ? nextfloat(y) : y
    end
end

set_zero_subnormals(yes::Bool) = ccall(:jl_set_zero_subnormals,Int32,(Int8,),yes)==0
get_zero_subnormals() = ccall(:jl_get_zero_subnormals,Int32,())!=0

end #module