Merge pull request #80 from project-eutopia/let_for_local_variables_i…

…n_children

`let` makes variables local to current context

lib/keisan/context.rb

@@ -73,7 +73,7 @@ def variable_is_modifiable?(name)
 
     def register_variable!(name, value, local: false)
       if !@variable_registry.shadowed.member?(name) && (transient? || !local && @parent&.variable_is_modifiable?(name))
-        @parent.register_variable!(name, value)
+        @parent.register_variable!(name, value, local: local)
       else
         @variable_registry.register!(name, value)
       end
@@ -93,7 +93,7 @@ def function_is_modifiable?(name)
 
     def register_function!(name, function, local: false)
       if transient? || !local && @parent&.function_is_modifiable?(name)
-        @parent.register_function!(name, function)
+        @parent.register_function!(name, function, local: local)
       else
         @function_registry.register!(name.to_s, function)
       end

spec/keisan/let_spec.rb

@@ -13,6 +13,8 @@
 
     expect(calculator.evaluate("{let x = 11; x*2}")).to eq 22
     expect(calculator.evaluate("x")).to eq 7
+    expect(calculator.evaluate("{x = 15; x}")).to eq 15
+    expect(calculator.evaluate("x")).to eq 15
   end
 
   it "raises error for single argument when not assignment" do
@@ -29,4 +31,27 @@
     expect(calculator.evaluate("x").value).to eq 3
     expect(calculator.evaluate("y").value).to eq 6
   end
+
+  it "will create local definitions in children contexts" do
+    calculator2 = Keisan::Calculator.new(context: calculator.context.spawn_child)
+
+    calculator.evaluate("x = 10")
+    calculator.evaluate("f(x) = x**2")
+
+    calculator2.evaluate("x = 20")
+    calculator2.evaluate("f(x) = x**3")
+
+    expect(calculator.evaluate("x")).to eq 20
+    expect(calculator.evaluate("f(2)")).to eq 8
+    expect(calculator2.evaluate("x")).to eq 20
+    expect(calculator2.evaluate("f(2)")).to eq 8
+
+    calculator2.evaluate("let x = 30")
+    calculator2.evaluate("let f(x) = x**4")
+
+    expect(calculator.evaluate("x")).to eq 20
+    expect(calculator.evaluate("f(2)")).to eq 8
+    expect(calculator2.evaluate("x")).to eq 30
+    expect(calculator2.evaluate("f(2)")).to eq 16
+  end
 end