From 5008c26a604876bcad09c868aa2ec4a2c8b64e35 Mon Sep 17 00:00:00 2001
From: bjculkin <bjculkin@mix.wvu.edu>
Date: Fri, 31 Mar 2017 08:54:20 -0400
Subject: Move Pratt Parser to new project

---
 .../bjc/utils/parserutils/pratt/PrattParser.java   | 190 +++++++++++++++++++++
 1 file changed, 190 insertions(+)
 create mode 100644 JPratt/src/main/java/bjc/utils/parserutils/pratt/PrattParser.java

(limited to 'JPratt/src/main/java/bjc/utils/parserutils/pratt/PrattParser.java')

diff --git a/JPratt/src/main/java/bjc/utils/parserutils/pratt/PrattParser.java b/JPratt/src/main/java/bjc/utils/parserutils/pratt/PrattParser.java
new file mode 100644
index 0000000..c53b4e1
--- /dev/null
+++ b/JPratt/src/main/java/bjc/utils/parserutils/pratt/PrattParser.java
@@ -0,0 +1,190 @@
+package bjc.utils.parserutils.pratt;
+
+import bjc.utils.data.ITree;
+import bjc.utils.funcutils.NumberUtils;
+import bjc.utils.parserutils.ParserException;
+import bjc.utils.parserutils.pratt.commands.DefaultNonInitialCommand;
+import bjc.utils.parserutils.pratt.commands.DefaultInitialCommand;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * A configurable Pratt parser for expressions.
+ * 
+ * @author EVE
+ * 
+ * @param <K>
+ *                The key type for the tokens.
+ * 
+ * @param <V>
+ *                The value type for the tokens.
+ * 
+ * @param <C>
+ *                The state type of the parser.
+ * 
+ *
+ */
+public class PrattParser<K, V, C> {
+	/*
+	 * Default commands that error when used.
+	 */
+	private final NonInitialCommand<K, V, C>	DEFAULT_LEFT_COMMAND	= new DefaultNonInitialCommand<>();
+	private final InitialCommand<K, V, C>		DEFAULT_NULL_COMMAND	= new DefaultInitialCommand<>();
+
+	/*
+	 * Left-commands that depend on what the null command was.
+	 */
+	private Map<K, Map<K, NonInitialCommand<K, V, C>>> dependantLeftCommands;
+
+	/*
+	 * The left commands.
+	 */
+	private Map<K, NonInitialCommand<K, V, C>> leftCommands;
+	/*
+	 * The initial commands.
+	 */
+	private Map<K, InitialCommand<K, V, C>> nullCommands;
+	/*
+	 * Initial commands only checked for statements.
+	 */
+	private Map<K, InitialCommand<K, V, C>> statementCommands;
+
+	/**
+	 * Create a new Pratt parser.
+	 * 
+	 */
+	public PrattParser() {
+		dependantLeftCommands = new HashMap<>();
+
+		leftCommands = new HashMap<>();
+		nullCommands = new HashMap<>();
+		statementCommands = new HashMap<>();
+	}
+
+	/**
+	 * Parse an expression.
+	 * 
+	 * @param precedence
+	 *                The initial precedence for the expression.
+	 * 
+	 * @param tokens
+	 *                The tokens for the expression.
+	 * 
+	 * @param state
+	 *                The state of the parser.
+	 * 
+	 * @param isStatement
+	 *                Whether or not to parse statements.
+	 * 
+	 * @return The expression as an AST.
+	 * 
+	 * @throws ParserException
+	 *                 If something goes wrong during parsing.
+	 */
+	public ITree<Token<K, V>> parseExpression(int precedence, TokenStream<K, V> tokens, C state,
+			boolean isStatement) throws ParserException {
+		if (precedence < 0) {
+			throw new IllegalArgumentException("Precedence must be greater than zero");
+		}
+
+		Token<K, V> initToken = tokens.current();
+		tokens.next();
+
+		K initKey = initToken.getKey();
+
+		ITree<Token<K, V>> ast;
+
+		if (isStatement && statementCommands.containsKey(initKey)) {
+			ast = statementCommands.getOrDefault(initKey, DEFAULT_NULL_COMMAND).denote(initToken,
+					new ParserContext<>(tokens, this, state));
+		} else {
+			ast = nullCommands.getOrDefault(initKey, DEFAULT_NULL_COMMAND).denote(initToken,
+					new ParserContext<>(tokens, this, state));
+		}
+
+		int rightPrec = Integer.MAX_VALUE;
+
+		while (true) {
+			Token<K, V> tok = tokens.current();
+
+			K key = tok.getKey();
+
+			NonInitialCommand<K, V, C> command = leftCommands.getOrDefault(key, DEFAULT_LEFT_COMMAND);
+
+			if (dependantLeftCommands.containsKey(initKey)) {
+				command = dependantLeftCommands.get(initKey).getOrDefault(key, command);
+			}
+
+			int leftBind = command.leftBinding();
+
+			if (NumberUtils.between(precedence, rightPrec, leftBind)) {
+				tokens.next();
+
+				ast = command.denote(ast, tok, new ParserContext<>(tokens, this, state));
+				rightPrec = command.nextBinding();
+			} else {
+				break;
+			}
+		}
+
+		return ast;
+	}
+
+	/**
+	 * Add a non-initial command to this parser.
+	 * 
+	 * @param marker
+	 *                The key that marks the command.
+	 * 
+	 * @param comm
+	 *                The command.
+	 */
+	public void addNonInitialCommand(K marker, NonInitialCommand<K, V, C> comm) {
+		leftCommands.put(marker, comm);
+	}
+
+	/**
+	 * Add a initial command to this parser.
+	 * 
+	 * @param marker
+	 *                The key that marks the command.
+	 * 
+	 * @param comm
+	 *                The command.
+	 */
+	public void addInitialCommand(K marker, InitialCommand<K, V, C> comm) {
+		nullCommands.put(marker, comm);
+	}
+
+	/**
+	 * Add a statement command to this parser.
+	 * 
+	 * The difference between statements and initial commands is that
+	 * statements can only appear at the start of the expression.
+	 * 
+	 * @param marker
+	 *                The key that marks the command.
+	 * 
+	 * @param comm
+	 *                The command.
+	 */
+	public void addStatementCommand(K marker, InitialCommand<K, V, C> comm) {
+		statementCommands.put(marker, comm);
+	}
+
+	/**
+	 * Add a dependant non-initial command to this parser.
+	 */
+	public void addDependantCommand(K dependant, K marker, NonInitialCommand<K, V, C> comm) {
+		if (dependantLeftCommands.containsKey(dependant)) {
+			dependantLeftCommands.get(dependant).put(marker, comm);
+		} else {
+			Map<K, NonInitialCommand<K, V, C>> comms = new HashMap<>();
+
+			comms.put(marker, comm);
+
+			dependantLeftCommands.put(dependant, comms);
+		}
+	}
+}
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