From c29e190bbd47b095a24bbffd7b2f26b7ee52bf69 Mon Sep 17 00:00:00 2001
From: Erik Schnetter <schnetter@gmail.com>
Date: Mon, 19 Jan 2015 15:29:33 -0500
Subject: [PATCH] Add `convert(Float16, BigFloat)`

---
 base/mpfr.jl | 5 +++++
 test/mpfr.jl | 1 +
 2 files changed, 6 insertions(+)

diff --git a/base/mpfr.jl b/base/mpfr.jl
index 607e6d4294174..091797268e825 100644
--- a/base/mpfr.jl
+++ b/base/mpfr.jl
@@ -174,11 +174,16 @@ convert(::Type{Float64}, x::BigFloat) =
     ccall((:mpfr_get_d,:libmpfr), Float64, (Ptr{BigFloat},Int32), &x, ROUNDING_MODE[end])
 convert(::Type{Float32}, x::BigFloat) =
     ccall((:mpfr_get_flt,:libmpfr), Float32, (Ptr{BigFloat},Int32), &x, ROUNDING_MODE[end])
+# TODO: avoid double rounding
+convert(::Type{Float16}, x::BigFloat) = convert(Float16, convert(Float32, x))
 
 call(::Type{Float64}, x::BigFloat, r::RoundingMode) =
     ccall((:mpfr_get_d,:libmpfr), Float64, (Ptr{BigFloat},Int32), &x, to_mpfr(r))
 call(::Type{Float32}, x::BigFloat, r::RoundingMode) =
     ccall((:mpfr_get_flt,:libmpfr), Float32, (Ptr{BigFloat},Int32), &x, to_mpfr(r))
+# TODO: avoid double rounding
+call(::Type{Float16}, x::BigFloat, r::RoundingMode) =
+    convert(Float16, call(Float32, x, r))
 
 promote_rule{T<:Real}(::Type{BigFloat}, ::Type{T}) = BigFloat
 promote_rule{T<:FloatingPoint}(::Type{BigInt},::Type{T}) = BigFloat
diff --git a/test/mpfr.jl b/test/mpfr.jl
index 613e5a90044c9..4ed130a5abf32 100644
--- a/test/mpfr.jl
+++ b/test/mpfr.jl
@@ -149,6 +149,7 @@ y = BigFloat(1)
 # convert from
 @test convert(Float64, BigFloat(0.5)) == 0.5
 @test convert(Float32, BigFloat(0.5)) == float32(0.5)
+@test convert(Float16, BigFloat(0.5)) == float16(0.5)
 
 # exponent
 x = BigFloat(0)