Add Base.tail(::NamedTuple). (#29595)

* Add Base.tail(::NamedTuple). Fixes #29572. * Simplify, as suggested by @JeffBezanson.
JuliaLang · Oct 26, 2018 · 010495f · 010495f
1 parent ffaf849
commit 010495f
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diff --git a/base/namedtuple.jl b/base/namedtuple.jl
@@ -273,6 +273,7 @@ values(nt::NamedTuple) = Tuple(nt)
 haskey(nt::NamedTuple, key::Union{Integer, Symbol}) = isdefined(nt, key)
 get(nt::NamedTuple, key::Union{Integer, Symbol}, default) = haskey(nt, key) ? getfield(nt, key) : default
 get(f::Callable, nt::NamedTuple, key::Union{Integer, Symbol}) = haskey(nt, key) ? getfield(nt, key) : f()
+tail(t::NamedTuple{names}) where names = NamedTuple{tail(names)}(t)
 
 @pure function diff_names(an::Tuple{Vararg{Symbol}}, bn::Tuple{Vararg{Symbol}})
  names = Symbol[]

diff --git a/test/namedtuple.jl b/test/namedtuple.jl
@@ -105,6 +105,9 @@ end
 @test get(()->0, (a=1, b=2, c=3), :a) == 1
 @test get(()->0, NamedTuple(), :a) == 0
 @test get(()->0, (a=1,), :b) == 0
+@test Base.tail((a = 1, b = 2.0, c = 'x')) ≡ (b = 2.0, c = 'x')
+@test Base.tail((a = 1, )) ≡ NamedTuple()
+@test_throws MethodError Base.tail(NamedTuple())
 
 # syntax errors