From c0bf1dc624f373872d5dd8e67d756d3ec70830e7 Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Wed, 12 Apr 2017 11:45:40 +0200
Subject: Implement support for variables, mixed types in data stack

---
 repl.d | 117 +++++++++++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 85 insertions(+), 32 deletions(-)

diff --git a/repl.d b/repl.d
index 9117c28..9f1d131 100644
--- a/repl.d
+++ b/repl.d
@@ -6,37 +6,51 @@ import std.typecons;
 import std.container : SList;
 import std.container : DList;
 
-SList!int               stack;
-DList!string[string]    words;
-Nullable!(DList!string) definition;
+import std.variant;
+
+alias Token = Algebraic!(int, string);
+
+SList!Token            stack;
+DList!Token[string]    words;
+int[string]            variables;
+Nullable!(DList!Token) definition;
 
 void startDefinition()
 in  { assert( definition.isNull); }
 out { assert(!definition.isNull); }
 body {
-	definition = DList!string();
+	definition = DList!Token();
 }
 
 void endDefinition()
 in  { assert(!definition.isNull); }
 out { assert( definition.isNull); }
 body {
-	auto wordToBeDefined = definition.front;
+	string wordToBeDefined;
+
+	definition.front.visit!(
+		(int    x   ) => wordToBeDefined = "",
+		(string name) => wordToBeDefined = name
+	);
 
-	if ( wordToBeDefined.isNumeric ) {
+	if ( wordToBeDefined == "" ) {
 		throw new Exception("words may not be numeric");
-	} else {
-		definition.removeFront;
-		words[wordToBeDefined] = definition;
-		definition.nullify;
 	}
+
+	definition.removeFront;
+	words[wordToBeDefined] = definition;
+	definition.nullify;
 }
 
-void append(ref Nullable!(DList!string) definition, string token) {
-	if ( token == ";" ) {
+void append(ref Nullable!(DList!Token) definition, int value) {
+	definition.insertBack(Token(value));
+}
+
+void append(ref Nullable!(DList!Token) definition, string word) {
+	if ( word == ";" ) {
 		endDefinition();
 	} else {
-		definition.insertBack(token);
+		definition.insertBack(Token(word));
 	}
 }
 
@@ -45,15 +59,28 @@ void evaluate(string word) {
 		case "§":
 			startDefinition();
 			break;
+		case "$":
+			string name  = stack.pop().get!string;
+			int    value = stack.pop().get!int;
+
+			variables[name] = value;
+			break;
+		case "@":
+			string name = stack.pop().get!string;
+
+			if ( name in variables ) {
+				stack.push(variables[name]);
+			}
+			break;
 		case "+":
-			auto a = stack.pop();
-			auto b = stack.pop();
+			int a = stack.pop().get!int;
+			int b = stack.pop().get!int;
 
 			stack.push(a + b);
 			break;
 		case "*":
-			auto a = stack.pop();
-			auto b = stack.pop();
+			int a = stack.pop().get!int;
+			int b = stack.pop().get!int;
 
 			stack.push(a * b);
 			break;
@@ -61,42 +88,68 @@ void evaluate(string word) {
 			writeln(stack.front);
 			break;
 		default:
-			foreach ( token; words[word] ) {
-				process(token);
+			if ( word in words ) {
+				foreach ( token; words[word] ) {
+					process(token);
+				}
+			} else {
+				stack.push(word);
 			}
 	}
 }
 
-void process(string token) {
-	if ( token.isNumeric ) {
-		stack.push(parse!int(token));
+void process(Token token) {
+	token.visit!(
+		(int    x   ) => process(x),
+		(string word) => process(word)
+	);
+}
+
+void process(int x) {
+	stack.push(x);
+}
+
+void process(string word) {
+	evaluate(word);
+}
+
+void push(ref SList!Token stack, int value) {
+	if ( definition.isNull ) {
+		stack.insertFront(Token(value));
 	} else {
-		evaluate(token);
+		definition.append(value);
 	}
 }
 
-void push(ref SList!int stack, int value) {
+void push(ref SList!Token stack, string word) {
 	if ( definition.isNull ) {
-		stack.insertFront(value);
+		stack.insertFront(Token(word));
 	} else {
-		definition.append(to!string(value));
+		definition.append(word);
 	}
 }
 
-int pop(ref SList!int stack) {
-	auto x = stack.front;
+Token pop(ref SList!Token stack) {
+	Token token = stack.front;
 	stack.removeFront;
-
-	return x;
+	return token;
 }
 
 void main() {
 	while ( !stdin.eof ) {
 		foreach ( token; stdin.readln.split ) {
 			if ( definition.isNull ) {
-				process(token);
+				if ( token.isNumeric ) {
+					process(parse!int(token));
+				} else {
+					process(token);
+				}
 			} else {
-				definition.append(token);
+				if ( token.isNumeric ) {
+					definition.append(parse!int(token));
+				} else {
+					definition.append(token);
+				}
 			}
 		}
 	}
-- 
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