Add FieldValues iterator (#46)

docs/src/index.md

@@ -156,3 +156,11 @@ Iterate over struct or named tuple property values.
 ```@docs
 propertyvalues
 ```
+
+## fieldvalues(x)
+
+Like `(getfield(x, i) for i in 1:nfields(x))` but faster.
+
+```@docs
+fieldvalues
+```

src/IterTools.jl

@@ -28,7 +28,8 @@ export
     flagfirst,
     takewhile,
     properties,
-    propertyvalues
+    propertyvalues,
+    fieldvalues
 
 function has_length(it)
     it_size = IteratorSize(it)
@@ -910,6 +911,8 @@ Base.IteratorSize(it::TakeWhile) = Base.SizeUnknown()
 eltype(::Type{TakeWhile{I}}) where {I} = eltype(I)
 IteratorEltype(::Type{TakeWhile{I}}) where {I} = IteratorEltype(I)
 
+# Properties
+
 struct Properties{T}
     x::T
     n::Int
@@ -940,6 +943,8 @@ function iterate(p::Properties, state=1)
     return ((name, getproperty(p.x, name)), state + 1)
 end
 
+# PropertyValues
+
 struct PropertyValues{T}
     x::T
     n::Int
@@ -958,6 +963,7 @@ julia> collect(propertyvalues(1 + 2im))
  2
 ```
 """
+
 function propertyvalues(x::T) where T
     names = propertynames(x)
     return PropertyValues{T}(x, length(names), names)
@@ -973,4 +979,32 @@ end
 length(p::Union{Properties, PropertyValues}) = p.n
 IteratorSize(::Type{<:Union{Properties, PropertyValues}}) = HasLength()
 
+# FieldValues
+
+struct FieldValues{T}
+    x::T
+end
+
+"""
+    fieldvalues(x)
+
+Iterate through the values of the fields of `x`.
+
+```jldoctest
+julia> collect(fieldvalues(1 + 2im))
+2-element Array{Any,1}:
+ 1
+ 2
+```
+"""
+fieldvalues(x::T) where {T} = FieldValues{T}(x)
+length(fs::FieldValues{T}) where {T} = fieldcount(T)
+IteratorSize(::Type{<:FieldValues}) = HasLength()
+
+function iterate(fs::FieldValues, state=1)
+    state > length(fs) && return nothing
+
+    return (getfield(fs.x, state), state + 1)
+end
+
 end # module IterTools

test/runtests.jl

@@ -455,5 +455,22 @@ include("testing_macros.jl")
         pv3 = propertyvalues(HasLength())
         @test collect(pv3) == Any[]
     end
+
+    @testset "fieldvalues" begin
+        fv1 = fieldvalues(1 + 2im)
+        @test IteratorEltype(fv1) isa HasEltype
+        @test eltype(fv1) == Any
+        @test IteratorSize(fv1) isa HasLength
+        @test length(fv1) == 2
+        @test collect(fv1) == Any[1, 2]
+
+        tp = ("", 1, 2.0)
+        fv2 = fieldvalues(tp)
+        @test collect(fv2) == collect(tp)
+
+        # HasLength used as an example no-field struct
+        fv3 = fieldvalues(HasLength())
+        @test collect(fv3) == Any[]
+    end
 end
 end