From 7bda9de511a5642efb297eae98c6ea7c42b27754 Mon Sep 17 00:00:00 2001
From: "Benjamin J. Culkin" <bjculkin@mix.wvu.edu>
Date: Wed, 25 Oct 2017 12:10:14 -0300
Subject: Start switch to maven modules

---
 base/src/bjc/dicelang/expr/Tokens.java | 96 ++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 base/src/bjc/dicelang/expr/Tokens.java

(limited to 'base/src/bjc/dicelang/expr/Tokens.java')

diff --git a/base/src/bjc/dicelang/expr/Tokens.java b/base/src/bjc/dicelang/expr/Tokens.java
new file mode 100644
index 0000000..287d2b4
--- /dev/null
+++ b/base/src/bjc/dicelang/expr/Tokens.java
@@ -0,0 +1,96 @@
+package bjc.dicelang.expr;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Contains per-instance state for token parsing.
+ *
+ * @author EVE
+ *
+ */
+public class Tokens {
+	/* Contains mappings from variable references to string names. */
+	private final Map<Integer, String> symTab;
+	/* Reverse index into the symbol table. */
+	private final Map<String, Integer> revSymTab;
+
+	/** Read-only view on the symbol table. */
+	public final Map<Integer, String> symbolTable;
+
+	/* Next index into the symbol table. */
+	private int nextSym;
+
+	/* Mapping from literal tokens to token types. */
+	private final Map<String, TokenType> litTokens;
+
+	/** Create a new set of tokens. */
+	public Tokens() {
+		/* Create tables. */
+		symTab = new HashMap<>();
+		revSymTab = new HashMap<>();
+
+		/* Init public view. */
+		symbolTable = Collections.unmodifiableMap(symTab);
+
+		/* Set sym ID. */
+		nextSym = 0;
+
+		/* 
+		 * Setup literal mappings.
+		 *
+		 * @NOTE
+		 * 	Should this be a static member?
+		 */
+		litTokens = new HashMap<>();
+		litTokens.put("+", TokenType.ADD);
+		litTokens.put("-", TokenType.SUBTRACT);
+		litTokens.put("*", TokenType.MULTIPLY);
+		litTokens.put("/", TokenType.DIVIDE);
+		litTokens.put("(", TokenType.OPAREN);
+		litTokens.put(")", TokenType.CPAREN);
+	}
+
+	/**
+	 * Convert the string representation of a token into a token.
+	 *
+	 * @param tok
+	 *                The string representation of the token.
+	 * @param raw
+	 *                The original string the token came from.
+	 *
+	 * @return The token the string represents.
+	 */
+	public Token lexToken(final String tok, final String raw) {
+		if (litTokens.containsKey(tok)) {
+			/* Return matching literal token. */
+			return new Token(litTokens.get(tok), raw, this);
+		}
+
+		/* Its a variable reference. */
+		return parseVRef(tok, raw);
+	}
+
+	/* Parse a variable reference. */
+	private Token parseVRef(final String tok, final String raw) {
+		final Token tk = new Token(TokenType.VREF, raw, this);
+
+		if (revSymTab.containsKey(tok)) {
+			/* Reuse the entry if it exists. */
+			tk.intValue = revSymTab.get(tok);
+		} else {
+			/* Create a new entry. */
+			tk.intValue = nextSym;
+
+			/* Record it. */
+			symTab.put(nextSym, tok);
+			revSymTab.put(tok, nextSym);
+
+			/* Next ID. */
+			nextSym += 1;
+		}
+
+		return tk;
+	}
+}
-- 
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