Implement Pratt parser.

1 files changed, 108 insertions, 0 deletions

diff --git a/BJC-Utils2/src/examples/java/bjc/utils/examples/parsing/PrattParserTest.java b/BJC-Utils2/src/examples/java/bjc/utils/examples/parsing/PrattParserTest.java
new file mode 100644
index 0000000..80e6130
--- /dev/null
+++ b/BJC-Utils2/src/examples/java/bjc/utils/examples/parsing/PrattParserTest.java
@@ -0,0 +1,108 @@
+package bjc.utils.examples.parsing;
+
+import bjc.utils.data.ITree;
+import bjc.utils.data.TransformIterator;
+import bjc.utils.parserutils.ParserException;
+import bjc.utils.parserutils.TokenSplitter;
+import bjc.utils.parserutils.pratt.PrattParser;
+import bjc.utils.parserutils.pratt.StringToken;
+import bjc.utils.parserutils.pratt.StringTokenStream;
+import bjc.utils.parserutils.pratt.Token;
+
+import com.google.common.collect.Iterators;
+
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.Scanner;
+
+import static bjc.utils.parserutils.pratt.LeftCommands.*;
+import static bjc.utils.parserutils.pratt.NullCommands.*;
+
+/**
+ * Simple test for pratt parser.
+ * 
+ * @author EVE
+ *
+ */
+public class PrattParserTest {
+	/**
+	 * Main method.
+	 * 
+	 * @param args
+	 *                Unused CLI args.
+	 */
+	public static void main(String[] args) {
+		TokenSplitter split = new TokenSplitter();
+		split.addDelimiter("+", "-", "*", "/");
+		split.addDelimiter("^", "!");
+		split.addDelimiter("(", ")");
+		split.compile();
+
+		PrattParser<String, String, Object> parser = new PrattParser<>();
+
+		parser.addNonInitialCommand("+", infixLeft(20));
+		parser.addNonInitialCommand("-", infixLeft(20));
+
+		parser.addNonInitialCommand("*", infixLeft(30));
+		parser.addNonInitialCommand("/", infixLeft(30));
+
+		parser.addNonInitialCommand("!", postfix(40));
+
+		parser.addNonInitialCommand("^", infixRight(50));
+
+		parser.addInitialCommand("(", grouping(0, ")", new StringToken("()", "()")));
+		parser.addInitialCommand("(literal)", leaf());
+
+		Scanner scn = new Scanner(System.in);
+
+		System.out.print("Enter a command (blank line to exit): ");
+		String ln = scn.nextLine();
+
+		while(!ln.trim().equals("")) {
+			String[] strangs = split.split(ln);
+
+			System.out.println("Split string: " + Arrays.toString(strangs));
+
+			Iterator<String> source = Iterators.forArray(strangs);
+
+			Iterator<Token<String, String>> tokens = new TransformIterator<>(source, (strang) -> {
+				String type;
+
+				switch(strang) {
+				case "+":
+				case "-":
+				case "*":
+				case "/":
+				case "(":
+				case ")":
+					type = strang;
+					break;
+				default:
+					type = "(literal)";
+				}
+
+				return new StringToken(type, strang);
+			});
+
+			try {
+				StringTokenStream tokenStream = new StringTokenStream(tokens);
+
+				/*
+				 * Prime stream.
+				 */
+				tokenStream.next();
+
+				ITree<Token<String, String>> tree = parser.parseExpression(0, tokenStream, null);
+
+				System.out.println("Parsed expression:\n" + tree);
+			} catch(ParserException pex) {
+				pex.printStackTrace();
+			}
+
+			System.out.print("Enter a command (blank line to exit): ");
+			ln = scn.nextLine();
+		}
+
+		scn.close();
+	}
+}