Implemented variable scopes

src/build/core/Variable.go

@@ -12,3 +12,19 @@ type Variable struct {
 	Register cpu.Register
 	Alive    int
 }
+
+// Variable returns the variable with the given name or `nil` if it doesn't exist.
+func (s *state) Variable(name string) *Variable {
+	return s.Scope()[name]
+}
+
+// VariableInRegister returns the variable that occupies the given register or `nil` if none occupy the register.
+func (s *state) VariableInRegister(register cpu.Register) *Variable {
+	for _, v := range s.Scope() {
+		if v.Register == register {
+			return v
+		}
+	}
+
+	return nil
+}