1 files changed, 153 insertions, 0 deletions
diff --git a/dice-lang/src/bjc/dicelang/expr/Parser.java b/dice-lang/src/bjc/dicelang/expr/Parser.java
new file mode 100644
index 0000000..e806a6f
--- /dev/null
+++ b/dice-lang/src/bjc/dicelang/expr/Parser.java
@@ -0,0 +1,153 @@
+package bjc.dicelang.expr;
+
+import bjc.utils.data.ITree;
+import bjc.utils.funcdata.FunctionalList;
+import bjc.utils.parserutils.TreeConstructor;
+
+import java.util.Arrays;
+import java.util.Scanner;
+
+/**
+ * Parser for simple math expressions.
+ *
+ * @author Ben Culkin
+ */
+public class Parser {
+	/**
+	 * Main method.
+	 *
+	 * @param args
+	 *                Unused CLI args.
+	 */
+	public static void main(String[] args) {
+		/*
+		 * Create our objects.
+		 */
+		Tokens toks = new Tokens();
+		Lexer lex = new Lexer();
+
+		/*
+		 * Prepare our input.
+		 */
+		Scanner scan = new Scanner(System.in);
+
+		/*
+		 * Read initial command.
+		 */
+		System.out.print("Enter a math expression (blank line to quit): ");
+		String ln = scan.nextLine().trim();
+
+		/*
+		 * Enter REPL loop.
+		 */
+		while(!ln.equals("")) {
+			/*
+			 * Print raw command.
+			 */
+			System.out.println("Raw command: " + ln);
+			System.out.println();
+
+			/*
+			 * Lex command to infix tokens.
+			 */
+			Token[] infixTokens = lex.lexString(ln, toks);
+			System.out.println("Lexed tokens: ");
+			for(Token tok : infixTokens) {
+				System.out.println("\t" + tok);
+			}
+
+			/*
+			 * Print out infix expression.
+			 */
+			System.out.print("Lexed expression: ");
+			for(Token tok : infixTokens) {
+				System.out.print(tok.toExpr() + " ");
+			}
+			System.out.println();
+			System.out.println();
+
+			/*
+			 * Shunt infix tokens to postfix tokens.
+			 */
+			Token[] postfixTokens = Shunter.shuntTokens(infixTokens);
+			System.out.println("Lexed tokens: ");
+			for(Token tok : postfixTokens) {
+				System.out.println("\t" + tok);
+			}
+
+			/*
+			 * Print out postfix tokens.
+			 */
+			System.out.print("Shunted expression: ");
+			for(Token tok : postfixTokens) {
+				System.out.print(tok.toExpr() + " ");
+			}
+			System.out.println();
+			System.out.println();
+
+			FunctionalList<Token> tokList = new FunctionalList<>(Arrays.asList(postfixTokens));
+			ITree<Token> ast = TreeConstructor.constructTree(tokList, tok -> tok.type.isOperator);
+
+			/*
+			 * Print the tree, then the canonical expression for it.
+			 */
+			System.out.println("Parsed tree");
+			System.out.println(ast.toString());
+			System.out.println("\nCanonical expr: " + toCanonicalExpr(ast));
+
+			System.out.println();
+
+			/*
+			 * Prompt for a new expression.
+			 */
+			System.out.print("Enter a math expression (blank line to quit): ");
+			ln = scan.nextLine().trim();
+		}
+
+		/*
+		 * Cleanup after ourselves.
+		 */
+		scan.close();
+	}
+
+	/*
+	 * Convert an expression to one that uses the smallest necessary amount
+	 * of parens.
+	 */
+	private static String toCanonicalExpr(ITree<Token> ast) {
+		Token data = ast.getHead();
+
+		if(ast.getChildrenCount() == 0)
+			/*
+			 * Handle leaf nodes
+			 */
+			return data.toExpr();
+		else {
+			ITree<Token> left = ast.getChild(0);
+			ITree<Token> right = ast.getChild(1);
+
+			String leftExpr = toCanonicalExpr(left);
+			String rightExpr = toCanonicalExpr(right);
+
+			/*
+			 * Add parens if the left was higher priority.
+			 */
+			if(left.getChildrenCount() == 0) {
+				if(left.getHead().type.operatorPriority >= data.type.operatorPriority) {
+					leftExpr = "(" + leftExpr + ")";
+				}
+			}
+
+			/*
+			 * Add parens if the right was higher priority.
+			 */
+			if(right.getChildrenCount() == 0) {
+				if(right.getHead().type.operatorPriority >= data.type.operatorPriority) {
+					rightExpr = "(" + rightExpr + ")";
+				}
+			}
+
+			return leftExpr + " " + data.toExpr() + " " + rightExpr;
+		}
+	}
+}