3 files changed, 164 insertions, 0 deletions
diff --git a/src/definition.d b/src/definition.d
new file mode 100644
index 0000000..dd4dddc
--- /dev/null
+++ b/src/definition.d
@@ -0,0 +1,57 @@
+module src.definition;
+
+import std.string;
+import std.variant;
+import std.typecons;
+import std.container : DList;
+
+import src.stack : Token;
+
+alias Words = DList!Token[string];
+
+Nullable!(DList!Token) definition;
+Words                  words;
+
+void start() {
+	definition = DList!Token();
+}
+
+void end() {
+	string wordToBeDefined;
+
+	definition.front.visit!(
+		(int    x   ) => wordToBeDefined = "",
+		(string name) => wordToBeDefined = name
+	);
+
+	if ( wordToBeDefined == "" ) {
+		throw new Exception("words may not be numeric");
+	}
+
+	definition.removeFront;
+	words[wordToBeDefined] = definition;
+	definition.nullify;
+}
+
+bool handle(int value) {
+	if ( definition.isNull ) {
+		return false;
+	} else {
+		definition.insertBack(Token(value));
+		return true;
+	}
+}
+
+bool handle(string word) {
+	if ( definition.isNull ) {
+		return false;
+	} else {
+		if ( word == ";" ) {
+			end();
+		} else {
+			definition.insertBack(Token(word));
+		}
+
+		return true;
+	}
+}
diff --git a/src/primitives.d b/src/primitives.d
new file mode 100644
index 0000000..0be6836
--- /dev/null
+++ b/src/primitives.d
@@ -0,0 +1,69 @@
+module src.primitives;
+
+import std.stdio;
+
+import src.stack;
+import src.definition;
+
+int[string] variables;
+
+bool evaluate(string word) {
+	switch ( word ) {
+		case "§":
+			src.definition.start;
+			return true;
+		case "$":
+			string name  = stack.pop.get!string;
+			int    value = stack.pop.get!int;
+
+			variables[name] = value;
+			return true;
+		case "@":
+			string name = stack.pop.get!string;
+
+			if ( name in variables ) {
+				stack.push(variables[name]);
+			}
+			return true;
+		case "+":
+			int b = stack.pop.get!int;
+			int a = stack.pop.get!int;
+
+			stack.push(a + b);
+			return true;
+		case "*":
+			int b = stack.pop.get!int;
+			int a = stack.pop.get!int;
+
+			stack.push(a * b);
+			return true;
+		case "/":
+			int b = stack.pop.get!int;
+			int a = stack.pop.get!int;
+
+			if ( b == 0 ) {
+				throw new Exception("division by 0 undefined");
+			} else {
+				stack.push(a / b);
+			}
+			return true;
+		case "%":
+			int b = stack.pop.get!int;
+			int a = stack.pop.get!int;
+
+			if ( b == 0 ) {
+				throw new Exception("modulo 0 undefined");
+			} else {
+				stack.push(a % b);
+			}
+			return true;
+		case ".":
+			stack.pop;
+			return true;
+		case "'":
+			writeln(stack.top);
+			return true;
+		default:
+			return false;
+	}
+}
diff --git a/src/stack.d b/src/stack.d
new file mode 100644
index 0000000..756dafc
--- /dev/null
+++ b/src/stack.d
@@ -0,0 +1,38 @@
+module src.stack;
+
+import std.variant;
+import std.string;
+import std.container : SList;
+
+static import src.definition;
+
+alias Token = Algebraic!(int, string);
+alias Stack = SList;
+
+Stack!Token stack;
+
+Token top(ref Stack!Token stack) {
+	if ( stack.empty ) {
+		throw new Exception("stack is empty");
+	} else {
+		return stack.front;
+	}
+}
+
+Token pop(ref Stack!Token stack) {
+	Token token = stack.top;
+	stack.removeFront;
+	return token;
+}
+
+void push(ref Stack!Token stack, int value) {
+	if ( !src.definition.handle(value) ) {
+		stack.insertFront(Token(value));
+	}
+}
+
+void push(ref Stack!Token stack, string word) {
+	if ( !src.definition.handle(word) ) {
+		stack.insertFront(Token(word));
+	}
+}