implement missing Base.front method for NamedTuples (#35458)

JuliaLang · Apr 14, 2020 · eb933c8 · eb933c8 · nanosoldier · Apr 14, 2020
1 parent 2a06eb6
commit eb933c8
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diff --git a/base/namedtuple.jl b/base/namedtuple.jl
@@ -289,6 +289,7 @@ 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)
+front(t::NamedTuple{names}) where names = NamedTuple{front(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
@@ -121,7 +121,10 @@ end
 @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 Base.front((a = 1, b = 2.0, c = 'x')) ≡ (a = 1, b = 2.0)
+@test Base.front((a = 1, )) ≡ NamedTuple()
 @test_throws ArgumentError Base.tail(NamedTuple())
+@test_throws ArgumentError Base.front(NamedTuple())
 
 # syntax errors