new method implementations for Stack

src/stack.jl

@@ -43,15 +43,16 @@ Get the top item from the stack. Sometimes called peek.
 Base.first(s::Stack) = last(s.store)
 Base.last(s::Stack) = first(s.store)
 
-function Base.push!(s::Stack, x)
-    push!(s.store, x)
-    return s
-end
+Base.push!(s::Stack, x) = (push!(s.store, x); s)
+Base.pushfirst!(s::Stack, x) = (pushfirst!(s.store, x); s)
 
 Base.pop!(s::Stack) = pop!(s.store)
+Base.popfirst!(s::Stack) = popfirst!(s.store)
 
 Base.empty!(s::Stack) = (empty!(s.store); s)
 
+Base.collect(s::Stack) = collect(s.store)
+
 Base.iterate(st::Stack, s...) = iterate(Iterators.reverse(st.store), s...)
 
 Iterators.reverse(s::Stack{T}) where {T} = DequeIterator{T}(s.store)

test/test_stack.jl

@@ -38,6 +38,28 @@
             @test isempty(s) == (i == n)
             @test length(s) == n - i
         end
+
+        for i = 1 : n
+            pushfirst!(s, i)
+            @test first(s) == 1
+            @test last(s) == i
+            @test !isempty(s)
+            @test length(s) == i
+        end
+
+        @test collect(s) == collect(n:-1:1)
+
+        for i = 1 : n
+            x = popfirst!(s)
+            @test x == n - i + 1
+            if i < n
+                @test first(s) == 1
+            else
+                @test_throws ArgumentError first(s)
+            end
+            @test isempty(s) == (i == n)
+            @test length(s) == n - i
+        end
     end
 
     @testset "==" begin