Simple RPN calculator is working as a first demo.

demos/calc.cpp

@@ -17,11 +17,12 @@ using std::string, std::wstring;
 
 enum class Event {
   NUMBER, ADD, SUB, MUL,
-  DIV, CLR, NEG, EQ, PUSH, POP
+  DIV, CLR, NEG, EQ, PUSH, DUP
 };
 
 const std::unordered_map<string, wstring> LABELS {
-  {"readout", L""}, {"clear", L"CLR"}, {"btn0", L"0"}, {"btn1", L"1"},
+  {"stack", L""}, {"readout", L""}, {"clear", L"CLR"},
+    {"btn0", L"0"}, {"btn1", L"1"},
     {"btn2", L"2"}, {"btn3", L"3"}, {"btn4", L"4"},
     {"btn5", L"5"}, {"btn6", L"6"}, {"btn7", L"7"},
     {"btn8", L"8"}, {"btn9", L"9"}, {"mul", L"*"},
@@ -38,20 +39,21 @@ const std::unordered_map<wchar_t, Event> EVENTS {
     {L'*', Event::MUL}, {L'-', Event::SUB},
     {L'+', Event::ADD}, {L'/', Event::DIV},
     {L'C', Event::CLR}, {L'^', Event::PUSH},
-    {L'±', Event::NEG}, {L'v', Event::POP},
+    {L'±', Event::NEG}, {L'v', Event::DUP},
     {L'=', Event::EQ} };
 
 
 struct Calculator {
   wstring input;
+  wstring curstack;
   std::deque<double> stack;
   double temp = 0.0;
   double result = 0.0;
 
-  void dump() {
-    fmt::println("STACK: ");
+  void display() {
+    curstack = L"";
     for(auto num : stack) {
-      fmt::println("{}", num);
+      curstack += fmt::format(L"{} ", num);
     }
   }
 
@@ -98,11 +100,9 @@ struct Calculator {
         input = L"";
         stack.clear();
         break;
-      case POP:
-        if(!stack.empty()) {
-          temp = stack.back();
-          input = fmt::format(L"{}", temp);
-          stack.pop_back();
+      case DUP:
+        if(stack.size() > 0) {
+          input = fmt::format(L"{}", stack.back());
         }
         break;
       case PUSH:
@@ -119,20 +119,26 @@ struct Calculator {
         }
         break;
       case EQ:
+        if(!stack.empty()) {
+          temp = stack.back();
+          input = fmt::format(L"{}", temp);
+          stack.pop_back();
+        }
         break;
     }
 
-    dump();
+    display();
   }
 };
 
 struct CalculatorUI {
   guecs::UI $gui;
-  Calculator $fsm;
+  Calculator $calc;
 
   CalculatorUI() {
     $gui.position(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);
     $gui.layout(
+        "[*%(400)stack|_|_|_]"
         "[*%(400)readout|_|_|_]"
         "[push|pop|clear|eq]"
         "[add|sub|mul|div]"
@@ -154,6 +160,8 @@ struct CalculatorUI {
 
       if(name == "readout") {
         $gui.set<guecs::Textual>(id, {L"", 40});
+      } else if(name == "stack") {
+        $gui.set<guecs::Textual>(id, {L"", 20});
       } else {
         $gui.set<guecs::Label>(id, { label });
         wchar_t op = label[0];
@@ -176,10 +184,9 @@ struct CalculatorUI {
   }
 
   void handle_button(wchar_t op) {
-    $fsm.event(EVENTS.at(op), op);
-    auto readout = $gui.entity("readout");
-    auto& label = $gui.get<guecs::Textual>(readout);
-    label.update($fsm.input);
+    $calc.event(EVENTS.at(op), op);
+    $gui.show_text("readout", $calc.input);
+    $gui.show_text("stack", $calc.curstack);
   }
 };