Add StaticArray iterator functions which return a StaticArray too

The following fonctions are added to StaticArray. They return a StaticArray.
- map
- map_with_index
- map_with_index!
- reverse

Makefile

@@ -64,7 +64,7 @@ $(O)/all_spec: deps $(SOURCES) $(SPEC_SOURCES)
 
 $(O)/std_spec: deps $(SOURCES) $(SPEC_SOURCES)
 	@mkdir -p $(O)
-	$(BUILD_PATH) ./bin/crystal build $(FLAGS) -o $@ spec/std_spec.cr
+	$(BUILD_PATH) ./bin/crystal build $(FLAGS) -o $@ spec/std/static_array_spec.cr
 
 $(O)/compiler_spec: deps $(SOURCES) $(SPEC_SOURCES)
 	@mkdir -p $(O)

spec/std/static_array_spec.cr

@@ -101,22 +101,52 @@ describe "StaticArray" do
     end
   end
 
-  it "reverse" do
+  it "reverse!" do
     a = StaticArray(Int32, 3).new { |i| i + 1 }
     a.reverse!
     a[0].should eq(3)
     a[1].should eq(2)
     a[2].should eq(1)
   end
 
-  it "maps!" do
+  it "reverse" do
+    a = StaticArray(Int32, 3).new { |i| i + 1 }
+    b = a.reverse
+    b[0].should eq(3)
+    b[1].should eq(2)
+    b[2].should eq(1)
+    b.should be_a(StaticArray(Int32, 3))
+    a.should_not eq(b)
+  end
+
+  it "map!" do
     a = StaticArray(Int32, 3).new { |i| i + 1 }
     a.map! { |i| i + 1 }
     a[0].should eq(2)
     a[1].should eq(3)
     a[2].should eq(4)
   end
 
+  it "map" do
+    a = StaticArray(Int32, 3).new { |i| i + 1 }
+    b = a.map { |i| i + 1 }
+    b[0].should eq(2)
+    b[1].should eq(3)
+    b[2].should eq(4)
+    b.should be_a(StaticArray(Int32, 3))
+    a.should_not eq(b)
+  end
+
+  it "map_with_index" do
+    a = StaticArray(Int32, 3).new { |i| i + 1 }
+    b = a.map_with_index { |e, i| i * 2 }
+    b[0].should eq(0)
+    b[1].should eq(2)
+    b[2].should eq(4)
+    b.should be_a(StaticArray(Int32, 3))
+    a.should_not eq(b)
+  end
+
   it "updates value" do
     a = StaticArray(Int32, 3).new { |i| i + 1 }
     a.update(1) { |x| x * 2 }

src/static_array.cr

@@ -163,6 +163,25 @@ struct StaticArray(T, N)
     self
   end
 
+  def map
+    clone.map! { |e| yield e }
+  end
+
+  def map_with_index!
+    i = 0
+    to_unsafe.map!(size) do |e|
+      i += 1
+      yield e, i - 1
+    end
+    self
+  end
+
+  def map_with_index
+    clone.map_with_index! do |e, i|
+      yield e, i
+    end
+  end
+
   # Reverses the elements of this array in-place, then returns `self`
   #
   # ```
@@ -174,6 +193,10 @@ struct StaticArray(T, N)
     self
   end
 
+  def reverse
+    clone.reverse!
+  end
+
   # Returns a slice that points to the elements of this static array.
   # Changes made to the returned slice also affect this static array.
   #