Added exists() as well as a static add() and mul() for times when it seems

weird to use those fluently. Might also add div() and sub() but I'm currently
wondering why those have varags constructors Div(SQLExpression... values). What
does foo / bar / baz mean exactly? That's a rhetorical question, division is
left associative, but it's still weird and too non-obvious IMO. foo - bar - baz
is also wonky.

src/java/com/samskivert/depot/Ops.java

@@ -22,10 +22,14 @@ package com.samskivert.depot;
 
 import java.util.Collection;
 
+import com.samskivert.depot.clause.SelectClause;
 import com.samskivert.depot.expression.FluentExp;
 import com.samskivert.depot.expression.SQLExpression;
+import com.samskivert.depot.operator.Add;
 import com.samskivert.depot.operator.And;
+import com.samskivert.depot.operator.Exists;
 import com.samskivert.depot.operator.Like;
+import com.samskivert.depot.operator.Mul;
 import com.samskivert.depot.operator.Not;
 import com.samskivert.depot.operator.Or;
 
@@ -36,7 +40,7 @@ import com.samskivert.depot.operator.Or;
 public class Ops
 {
     /**
-     * Creates a {@link Not} with the supplied target expression.
+     * Creates a NOT expression with the supplied target expression.
      */
     public static SQLExpression not (SQLExpression expr)
     {
@@ -44,7 +48,7 @@ public class Ops
     }
 
     /**
-     * Creates an {@link And} with the supplied target expressions.
+     * Creates an AND expression with the supplied target expressions.
      */
     public static FluentExp and (Collection<? extends SQLExpression> conditions)
     {
@@ -52,7 +56,7 @@ public class Ops
     }
 
     /**
-     * Creates an {@link And} with the supplied target expressions.
+     * Creates an AND expression with the supplied target expressions.
      */
     public static FluentExp and (SQLExpression... conditions)
     {
@@ -60,7 +64,7 @@ public class Ops
     }
 
     /**
-     * Creates an {@link Or} with the supplied target expressions.
+     * Creates an OR expression with the supplied target expressions.
      */
     public static FluentExp or (Collection<? extends SQLExpression> conditions)
     {
@@ -68,22 +72,50 @@ public class Ops
     }
 
     /**
-     * Creates an {@link Or} with the supplied target expressions.
+     * Creates an OR expression with the supplied target expressions.
      */
     public static FluentExp or (SQLExpression... conditions)
     {
         return new Or(conditions);
     }
 
-    /** Returns an expression that matches when the source is like the supplied value. */
+    /**
+     * Returns an expression that matches when the source is like the supplied value.
+     */
     public static FluentExp like (SQLExpression source, Comparable<?> value)
     {
         return new Like(source, value);
     }
 
-    /** Returns an expression that matches when the source is like the supplied expression. */
+    /**
+     * Returns an expression that matches when the source is like the supplied expression.
+     */
     public static FluentExp like (SQLExpression source, SQLExpression expr)
     {
         return new Like(source, expr);
     }
+
+    /**
+     * Creates an EXISTS expression with the supplied select clause.
+     */
+    public static SQLExpression exists (SelectClause target)
+    {
+        return new Exists(target);
+    }
+
+    /**
+     * Adds the supplied expressions together.
+     */
+    public static FluentExp add (SQLExpression... exprs)
+    {
+        return new Add(exprs);
+    }
+
+    /**
+     * Multiplies the supplied expressions together.
+     */
+    public static FluentExp mul (SQLExpression... exprs)
+    {
+        return new Mul(exprs);
+    }
 }