Add document for table constraint proof object.

DB-record/src/Database/Record/KeyConstraint.hs

@@ -11,7 +11,11 @@
 -- Maintainer  : ex8k.hibino@gmail.com
 -- Stability   : experimental
 -- Portability : unknown
+--
+-- This module provides proof object definitions
+-- of table constraint specifiey by keys.
 module Database.Record.KeyConstraint (
+  -- * Constraint specifiey by keys
   KeyConstraint, index, specifyKeyConstraint,
 
   Unique, UniqueConstraint,
@@ -20,6 +24,7 @@ module Database.Record.KeyConstraint (
   Primary, PrimaryConstraint,
   unique, notNull,
 
+  -- * Deriviations
   leftKeyConstraint,
   HasKeyConstraint (keyConstraint),
 
@@ -29,44 +34,69 @@ module Database.Record.KeyConstraint (
   specifyNotNullValue
   ) where
 
+
+-- | Proof object to specify table constraint
+--   for table record type 'r' and constraint 'c'.
 newtype KeyConstraint c r = KeyConstraint Int
 
+-- | Index of key which specifies table constraint.
 index :: KeyConstraint c r -> Int
 index (KeyConstraint i) = i
 
+-- | Constraint type. Unique key.
 data Unique
+
+-- | Constraint type. Not-null key.
 data NotNull
+
+-- | Constraint type. Primary key.
 data Primary
 
+-- | Specialized unique constraint.
 type UniqueConstraint  = KeyConstraint Unique
+
+-- | Specialized not-null constraint.
 type NotNullConstraint = KeyConstraint NotNull
+
+-- | Specialized primary constraint.
 type PrimaryConstraint = KeyConstraint Primary
 
+-- | Unsafely generate proof object using specified key index.
 specifyKeyConstraint :: Int -> KeyConstraint c r
 specifyKeyConstraint =  KeyConstraint
 
+-- | Derivation rule for 'UniqueConstraint'.
 unique :: PrimaryConstraint r -> UniqueConstraint r
 unique =  specifyKeyConstraint . index
 
+-- | Derivation rule for 'NotNullConstraint'.
 notNull :: PrimaryConstraint r -> NotNullConstraint r
 notNull =  specifyKeyConstraint . index
 
 
+-- | Derivation rule of 'KeyConstraint' for tuple (,) type.
 leftKeyConstraint :: KeyConstraint k a -> KeyConstraint k (a, b)
 leftKeyConstraint pa = KeyConstraint (index pa)
 
+-- | Interface of inference rule for 'KeyConstraint' proof object.
 class HasKeyConstraint c a where
   keyConstraint :: KeyConstraint c a
 
+-- | Inference rule of 'KeyConstraint' for tuple (,) type.
 instance HasKeyConstraint c a => HasKeyConstraint c (a, b) where
   keyConstraint = leftKeyConstraint keyConstraint
 
+-- | Inferred 'UniqueConstraint' proof object.
+--   Record type 'r' has unique key which is derived 'r' has primary key.
 derivedUniqueConstraint :: HasKeyConstraint Primary r => UniqueConstraint r
 derivedUniqueConstraint =  unique keyConstraint
 
+-- | Inferred 'NotNullConstraint' proof object.
+--   Record type 'r' has not-null key which is derived 'r' has primary key.
 derivedNotNullConstraint :: HasKeyConstraint Primary r => NotNullConstraint r
 derivedNotNullConstraint =  notNull keyConstraint
 
 
-specifyNotNullValue :: KeyConstraint NotNull a
+-- | 'NotNullConstraint' proof object of single field value. This is unsafe.
+specifyNotNullValue :: NotNullConstraint a
 specifyNotNullValue =  specifyKeyConstraint 0