     
     private var collations = Set<DatabaseCollation>()
     
-    /// TODO
+    /// Add or redefine a collation.
+    ///
+    ///     let collation = DatabaseCollation("localized_standard") { (string1, string2) in
+    ///         return (string1 as NSString).localizedStandardCompare(string2)
+    ///     }
+    ///     db.addCollation(collation)
+    ///     try db.execute("CREATE TABLE files (name TEXT COLLATE LOCALIZED_STANDARD")
+    ///
+    /// - parameter collation: A collation.
     public func addCollation(collation: DatabaseCollation) {
         collations.remove(collation)
         collations.insert(collation)

// =========================================================================
// MARK: - Functions

/// TODO
public class DatabaseFunction : Hashable {
    let name: String
    let argumentCount: Int32

    
    /// Returns a collation.
    ///
    ///     let collation = DatabaseCollation("localized_standard") { (string1, string2) in
    ///         return (string1 as NSString).localizedStandardCompare(string2)
    ///     }
    ///     db.addCollation(collation)
    ///     try db.execute("CREATE TABLE files (name TEXT COLLATE LOCALIZED_STANDARD")
    ///
    /// - parameter name: The function name.
    /// - parameter function: A function that compares two strings.
