From 9ce65c5a963b03ee97fe9cb6c5aa65a3c04a80a8 Mon Sep 17 00:00:00 2001
From: yzhou <yujiao.zhou@gmail.com>
Date: Tue, 21 Apr 2015 10:34:27 +0100
Subject: initial version

---
 .../ox/cs/pagoda/util/ConjunctiveQueryHelper.java  | 70 ++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 src/uk/ac/ox/cs/pagoda/util/ConjunctiveQueryHelper.java

(limited to 'src/uk/ac/ox/cs/pagoda/util/ConjunctiveQueryHelper.java')

diff --git a/src/uk/ac/ox/cs/pagoda/util/ConjunctiveQueryHelper.java b/src/uk/ac/ox/cs/pagoda/util/ConjunctiveQueryHelper.java
new file mode 100644
index 0000000..937c2c4
--- /dev/null
+++ b/src/uk/ac/ox/cs/pagoda/util/ConjunctiveQueryHelper.java
@@ -0,0 +1,70 @@
+package uk.ac.ox.cs.pagoda.util;
+
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.LinkedList;
+
+public class ConjunctiveQueryHelper {
+	
+	public static String[][] getAnswerVariables(String queryText) {
+		Collection<String> disVars = new LinkedList<String>(), undisVars = new LinkedList<String>(); 
+		for (String var: getAllVariables(queryText))
+			if (var.startsWith("?")) disVars.add(var.substring(1)); 
+			else undisVars.add(var.substring(2));
+		
+		String[] distinguishedVariables = disVars.toArray(new String[0]); 
+		String[] undistinguishedVariables = undisVars.toArray(new String[0]); 
+		String[] answerVariables = null;
+		
+		String uppercase = queryText.toUpperCase(); 
+		int selectIndex = uppercase.indexOf("SELECT");
+		int whereIndex = uppercase.indexOf("WHERE"); 
+		String selectClause = queryText.substring(selectIndex + 6, whereIndex); 
+		if (selectClause.contains("*")) answerVariables = distinguishedVariables;
+		else {
+			String[] terms = selectClause.split(" ");
+			int num = 0; 
+			for (int i = 0; i < terms.length; ++i)
+				if (terms[i].startsWith("?")) ++num;
+			answerVariables = new String[num]; 
+			for (int i = 0, j = 0; i < terms.length; ++i)
+				if (terms[i].startsWith("?"))
+					answerVariables[j++] = terms[i].substring(1);
+		}
+	
+		if (answerVariables != distinguishedVariables) {
+			int index = 0; 
+			for (; index < answerVariables.length; ++index) {
+				distinguishedVariables[index] = answerVariables[index]; 
+				disVars.remove(answerVariables[index]); 
+			}
+			for (String var: disVars)
+				distinguishedVariables[index++] = var; 
+		}
+		
+		return new String[][] { answerVariables, distinguishedVariables, undistinguishedVariables };
+	}
+
+	private static Collection<String> getAllVariables(String queryText) {
+		Collection<String> vars = new HashSet<String>(); 
+		int start, end = 0; 
+		char ch; 
+		while ((start = queryText.indexOf("?", end)) != -1) {
+			end = start + 1; 
+			while (end + 1 < queryText.length() && (ch = queryText.charAt(end + 1)) != '\n' && ch != ' ') 
+				++end;
+			vars.add(queryText.substring(start, end + 1)); 
+		}
+		
+		end = 0; 
+		while ((start = queryText.indexOf("_:", end)) != -1) {
+			end = start + 1; 
+			while (end + 1 < queryText.length() && (ch = queryText.charAt(end + 1)) != '\n' && ch != ' ') 
+				++end;
+			vars.add(queryText.substring(start, end + 1)); 
+		}
+
+		return vars; 
+	}
+
+}
-- 
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