Add translation of selection conditions

src/main/java/uk/ac/ed/pguaglia/real/lang/BinaryCondition.java

@@ -35,4 +35,21 @@ public abstract class BinaryCondition extends Condition {
 		sign.addAll(rightCondition.signature());
 		return sign;
 	}
+
+	@Override
+	public String toSQL() {
+		String op;
+		switch (this.getType()) {
+		case CONJUNCTION:
+			op = "AND";
+			break;
+		case DISJUNCTION:
+			op = "OR";
+			break;
+		default:
+			throw new IllegalStateException();
+		}
+		return String.format("(%s %s %s)",
+				this.leftCondition.toSQL(), op, this.rightCondition.toSQL());
+	}
 }

src/main/java/uk/ac/ed/pguaglia/real/lang/Condition.java

@@ -53,4 +53,6 @@ public abstract class Condition {
 	public abstract boolean satisfied(String[] record, Map<String,Integer> attr);
 
 	public abstract Set<String> signature();
+
+	public abstract String toSQL();
 }

src/main/java/uk/ac/ed/pguaglia/real/lang/Conjunction.java

@@ -13,4 +13,10 @@ public class Conjunction extends BinaryCondition {
 		return super.leftCondition.satisfied(record, attr)
 				&& super.rightCondition.satisfied(record, attr);
 	}
+
+	@Override
+	public String toSQL() {
+		// TODO Auto-generated method stub
+		return null;
+	}
 }

src/main/java/uk/ac/ed/pguaglia/real/lang/Disjunction.java

@@ -13,4 +13,10 @@ public class Disjunction extends BinaryCondition {
 		return super.leftCondition.satisfied(record, attr)
 				|| super.rightCondition.satisfied(record, attr);
 	}
+
+	@Override
+	public String toSQL() {
+		// TODO Auto-generated method stub
+		return null;
+	}
 }

src/main/java/uk/ac/ed/pguaglia/real/lang/Equality.java

@@ -4,6 +4,8 @@ import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
 
+import uk.ac.ed.pguaglia.real.db.Database;
+
 public class Equality extends Condition {
 
 	private Term left;
@@ -48,4 +50,13 @@ public class Equality extends Condition {
 		String v2 = right.getValue(record, attr);
 		return v1.equals(v2);
 	}
+
+	@Override
+	public String toSQL() {
+		String left = this.left.isAttribute() ?
+				Database.encode(this.left.getValue()) : "'" + this.left.getValue() + "'";
+		String right = this.right.isAttribute() ?
+				Database.encode(this.right.getValue()) : "'" + this.right.getValue() + "'";
+		return  left + " = " + right;
+	}
 }

src/main/java/uk/ac/ed/pguaglia/real/lang/LessThan.java

@@ -4,6 +4,8 @@ import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
 
+import uk.ac.ed.pguaglia.real.db.Database;
+
 public class LessThan extends Condition {
 
 	private Term left;
@@ -50,4 +52,13 @@ public class LessThan extends Condition {
 			return v1.compareTo(v2) < 0;			
 		}
 	}
+
+	@Override
+	public String toSQL() {
+		String left = this.left.isAttribute() ?
+				Database.encode(this.left.getValue()) : "'" + this.left.getValue() + "'";
+		String right = this.right.isAttribute() ?
+				Database.encode(this.right.getValue()) : "'" + this.right.getValue() + "'";
+		return  left + " < " + right;
+	}
 }

src/main/java/uk/ac/ed/pguaglia/real/lang/Negation.java

@@ -30,4 +30,9 @@ public class Negation extends Condition {
 	public boolean satisfied(String[] record, Map<String, Integer> attr) {
 		return !cond.satisfied(record, attr);
 	}
+
+	@Override
+	public String toSQL() {
+		return "NOT (" + this.cond.toSQL() + ")";
+	}
 }

src/main/java/uk/ac/ed/pguaglia/real/lang/Selection.java

@@ -68,10 +68,7 @@ public class Selection extends UnaryOperation {
 
 	@Override
 	public String toSQL(boolean setEval) {
-		String cond = this.cond.toString()
-				.replace(Condition.Type.CONJUNCTION.getConnective(), " AND ")
-				.replace(Condition.Type.DISJUNCTION.getConnective(), " OR ")
-				.replace(Condition.Type.NEGATION.getConnective(), " NOT ");
-		return String.format("SELECT * FROM (%s) Q WHERE %s", this.operand.toSQL(setEval), cond);
+		return String.format("SELECT * FROM (%s) Q WHERE %s",
+				this.operand.toSQL(setEval), this.cond.toSQL());
 	}
 }