From 54e034aac5500d1f8264e6454163ab56e2ddfe78 Mon Sep 17 00:00:00 2001
From: Tim Holy <tim.holy@gmail.com>
Date: Sat, 30 Apr 2016 11:13:41 -0500
Subject: [PATCH] Make max/min synonyms for scalarmax/scalarmin in reductions

Fixes #16133
---
 base/reduce.jl    | 10 ++++++++++
 base/reducedim.jl | 28 +++++++++++++---------------
 test/reducedim.jl |  4 ++++
 3 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/base/reduce.jl b/base/reduce.jl
index 7d8278aa73431..37478824ae839 100644
--- a/base/reduce.jl
+++ b/base/reduce.jl
@@ -28,6 +28,8 @@ r_promote(::typeof(scalarmax), x::WidenReduceResult) = x
 r_promote(::typeof(scalarmin), x::WidenReduceResult) = x
 r_promote(::typeof(scalarmax), x) = x
 r_promote(::typeof(scalarmin), x) = x
+r_promote(::typeof(max), x) = r_promote(scalarmax, x)
+r_promote(::typeof(min), x) = r_promote(scalarmin, x)
 
 
 ## foldl && mapfoldl
@@ -126,6 +128,8 @@ mr_empty(::typeof(abs2), op::typeof(+), T) = r_promote(op, abs2(zero(T)::T))
 mr_empty(::typeof(identity), op::typeof(*), T) = r_promote(op, one(T)::T)
 mr_empty(::typeof(abs), op::typeof(scalarmax), T) = abs(zero(T)::T)
 mr_empty(::typeof(abs2), op::typeof(scalarmax), T) = abs2(zero(T)::T)
+mr_empty(::typeof(abs), op::typeof(max), T) = mr_empty(abs, scalarmax, T)
+mr_empty(::typeof(abs2), op::typeof(max), T) = mr_empty(abs2, scalarmax, T)
 mr_empty(f, op::typeof(&), T) = true
 mr_empty(f, op::typeof(|), T) = false
 
@@ -277,6 +281,9 @@ prod(a) = mapreduce(identity, *, a)
 
 ## maximum & minimum
 
+function mapreduce_impl(f, op::typeof(max), A::AbstractArray, first::Int, last::Int)
+    mapreduce_impl(f, scalarmax, A, first, last)
+end
 function mapreduce_impl(f, op::typeof(scalarmax), A::AbstractArray, first::Int, last::Int)
     # locate the first non NaN number
     v = f(A[first])
@@ -297,6 +304,9 @@ function mapreduce_impl(f, op::typeof(scalarmax), A::AbstractArray, first::Int,
     v
 end
 
+function mapreduce_impl(f, op::typeof(min), A::AbstractArray, first::Int, last::Int)
+    mapreduce_impl(f, scalarmin, A, first, last)
+end
 function mapreduce_impl(f, op::typeof(scalarmin), A::AbstractArray, first::Int, last::Int)
     # locate the first non NaN number
     v = f(A[first])
diff --git a/base/reducedim.jl b/base/reducedim.jl
index fa2a1e6a1b832..3453da705b183 100644
--- a/base/reducedim.jl
+++ b/base/reducedim.jl
@@ -74,7 +74,7 @@ end
 
 ## initialization
 
-for (Op, initfun) in ((:(typeof(+)), :zero), (:(typeof(*)), :one), (:(typeof(scalarmax)), :typemin), (:(typeof(scalarmin)), :typemax))
+for (Op, initfun) in ((:(typeof(+)), :zero), (:(typeof(*)), :one), (:(typeof(scalarmax)), :typemin), (:(typeof(scalarmin)), :typemax), (:(typeof(max)), :typemin), (:(typeof(min)), :typemax))
     @eval initarray!{T}(a::AbstractArray{T}, ::$(Op), init::Bool) = (init && fill!(a, $(initfun)(T)); a)
 end
 
@@ -94,32 +94,30 @@ reducedim_initarray0{T}(A::AbstractArray, region, v0::T) = reducedim_initarray0(
 #
 promote_union(T::Union) = promote_type(T.types...)
 promote_union(T) = T
+
 function reducedim_init{S}(f, op::typeof(+), A::AbstractArray{S}, region)
-    T = promote_union(S)
-    if method_exists(zero, Tuple{Type{T}})
-        x = f(zero(T))
-        z = zero(x) + zero(x)
-        Tr = typeof(z) == typeof(x) && !isbits(T) ? T : typeof(z)
-    else
-        z = zero(sum(f, A))
-        Tr = typeof(z)
-    end
-    return reducedim_initarray(A, region, z, Tr)
+    _reducedim_init(f, op, zero, sum, A, region)
 end
-
 function reducedim_init{S}(f, op::typeof(*), A::AbstractArray{S}, region)
-    T = promote_union(S)
+    _reducedim_init(f, op, one, prod, A, region)
+end
+function _reducedim_init(f, op, fv, fop, A, region)
+    T = promote_union(eltype(A))
     if method_exists(zero, Tuple{Type{T}})
         x = f(zero(T))
-        z = one(x) * one(x)
+        z = op(fv(x), fv(x))
         Tr = typeof(z) == typeof(x) && !isbits(T) ? T : typeof(z)
     else
-        z = one(prod(f, A))
+        z = fv(fop(f, A))
         Tr = typeof(z)
     end
     return reducedim_initarray(A, region, z, Tr)
 end
 
+reducedim_init{T}(f, op::typeof(max), A::AbstractArray{T}, region) = reducedim_init(f, scalarmax, A, region)
+reducedim_init{T}(f, op::typeof(min), A::AbstractArray{T}, region) = reducedim_init(f, scalarmin, A, region)
+reducedim_init{T}(f::Union{typeof(abs),typeof(abs2)}, op::typeof(max), A::AbstractArray{T}, region) = reducedim_init(f, scalarmax, A, region)
+
 reducedim_init{T}(f, op::typeof(scalarmax), A::AbstractArray{T}, region) = reducedim_initarray0(A, region, typemin(f(zero(T))))
 reducedim_init{T}(f, op::typeof(scalarmin), A::AbstractArray{T}, region) = reducedim_initarray0(A, region, typemax(f(zero(T))))
 reducedim_init{T}(f::Union{typeof(abs),typeof(abs2)}, op::typeof(scalarmax), A::AbstractArray{T}, region) =
diff --git a/test/reducedim.jl b/test/reducedim.jl
index 6775ed1de5028..9d2b66a99bbd3 100644
--- a/test/reducedim.jl
+++ b/test/reducedim.jl
@@ -99,6 +99,10 @@ A = reshape(1:6, 3, 2)
 @test typeof(@inferred(Base.prod(abs, [1.0+1.0im], 1))) == Vector{Float64}
 @test typeof(@inferred(Base.prod(abs2, [1.0+1.0im], 1))) == Vector{Float64}
 
+# min/max
+@test reducedim(max, A, 1) == [3 6]
+@test reducedim(min, A, 2) == reshape([1,2,3], 3, 1)
+
 # Heterogeneously typed arrays
 @test sum(Union{Float32, Float64}[1.0], 1) == [1.0]
 @test prod(Union{Float32, Float64}[1.0], 1) == [1.0]