From b638c4887ab77ad0949aa6381db40e6d438611ff Mon Sep 17 00:00:00 2001
From: Tim Holy <tim.holy@gmail.com>
Date: Tue, 26 Nov 2019 13:24:03 -0600
Subject: [PATCH] Add support for CheckedArithmetic

---
 Project.toml             |  4 ++++
 src/FixedPointNumbers.jl |  4 ++++
 src/fixed.jl             |  7 +++++++
 src/normed.jl            |  7 +++++++
 test/normed.jl           | 22 +++++++++++++++++++++-
 5 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/Project.toml b/Project.toml
index 60fd45cd..0482f844 100644
--- a/Project.toml
+++ b/Project.toml
@@ -2,8 +2,12 @@ name = "FixedPointNumbers"
 uuid = "53c48c17-4a7d-5ca2-90c5-79b7896eea93"
 version = "0.6.1"
 
+[deps]
+CheckedArithmetic = "2c4a1fb8-30c1-4c71-8b84-dff8d59868ee"
+
 [compat]
 julia = "1"
+CheckedArithmetic = "0.1"
 
 [extras]
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
diff --git a/src/FixedPointNumbers.jl b/src/FixedPointNumbers.jl
index ccd86e50..9ad8b07e 100644
--- a/src/FixedPointNumbers.jl
+++ b/src/FixedPointNumbers.jl
@@ -12,6 +12,8 @@ import Base: ==, <, <=, -, +, *, /, ~, isapprox,
 
 using Base: @pure
 
+using CheckedArithmetic
+
 # T => BaseType
 # f => Number of bits reserved for fractional part
 abstract type FixedPoint{T <: Integer, f} <: Real end
@@ -199,4 +201,6 @@ end
 rand(::Type{T}) where {T <: FixedPoint} = reinterpret(T, rand(rawtype(T)))
 rand(::Type{T}, sz::Dims) where {T <: FixedPoint} = reinterpret(T, rand(rawtype(T), sz))
 
+CheckedArithmetic.safearg_type(::Type{T}) where T<:FixedPoint = Float64
+
 end # module
diff --git a/src/fixed.jl b/src/fixed.jl
index 3576a610..f237a640 100644
--- a/src/fixed.jl
+++ b/src/fixed.jl
@@ -97,3 +97,10 @@ end
 
 # TODO: Document and check that it still does the right thing.
 decompose(x::Fixed{T,f}) where {T,f} = x.i, -f, 1
+
+CheckedArithmetic.accumulatortype(::typeof(+), ::Type{Fixed{T,f}}) where {T,f} =
+    Fixed{accumulatortype(+, T), f}
+CheckedArithmetic.accumulatortype(::typeof(-), ::Type{Fixed{T,f}}) where {T,f} =
+    Fixed{accumulatortype(-, T), f}
+CheckedArithmetic.accumulatortype(::typeof(*), ::Type{Fixed{T,f}}) where {T,f} =
+    floattype(Fixed{T,f})
diff --git a/src/normed.jl b/src/normed.jl
index 737657b4..5d4be612 100644
--- a/src/normed.jl
+++ b/src/normed.jl
@@ -333,3 +333,10 @@ if !signbit(signed(unsafe_trunc(UInt, -12.345)))
         unsafe_trunc(T, unsafe_trunc(typeof(signed(zero(T))), x))
     end
 end
+
+CheckedArithmetic.accumulatortype(::typeof(+), ::Type{Normed{T,f}}) where {T,f} =
+    Normed{accumulatortype(+, T), f}
+CheckedArithmetic.accumulatortype(::typeof(-), ::Type{Normed{T,f}}) where {T,f} =
+    floattype(Normed{T,f})
+CheckedArithmetic.accumulatortype(::typeof(*), ::Type{Normed{T,f}}) where {T,f} =
+    floattype(Normed{T,f})
diff --git a/test/normed.jl b/test/normed.jl
index 6fb4d125..c3454b50 100644
--- a/test/normed.jl
+++ b/test/normed.jl
@@ -1,4 +1,4 @@
-using FixedPointNumbers, Test
+using FixedPointNumbers, CheckedArithmetic, Test
 
 @testset "reinterpret" begin
     @test reinterpret(N0f8, 0xa2).i  === 0xa2
@@ -367,6 +367,22 @@ end
     @test 1.0*a == bd*ad
 end
 
+function sum_naive(A::AbstractArray)
+    s = zero(eltype(A))
+    for a in A
+        s += a
+    end
+    return s
+end
+
+function sumsquares(A::AbstractArray)
+    s = zero(accumulatortype(eltype(A)))
+    for a in A
+        s += acc(a)^2
+    end
+    return s
+end
+
 @testset "reductions" begin
     a = N0f8[reinterpret(N0f8, 0xff), reinterpret(N0f8, 0xff)]
     @test sum(a) == 2.0
@@ -376,6 +392,10 @@ end
     acmp = Float64(a[1])*Float64(a[2])
     @test prod(a) == acmp
     @test prod(a, dims=1) == [acmp]
+
+    a = reinterpret(N0f8, [0x01:0xff;])
+    @test_throws ArgumentError @check sum_naive(a) atol=1e-4
+    @check sumsquares(a) atol=1e-4
 end
 
 @testset "rand" begin