HsLua.Marshalling.Peekers

Functions which unmarshal and retrieve Haskell values from Lua's stack.

Peeking values from the stack

Primitives

peekNil :: Peeker e ()

Succeeds if the value at the given index is nil.

peekNoneOrNil :: Peeker e ()

Succeeds if the given index is not valid or if the value at this index is nil.

peekBool :: Peeker e Bool

Retrieves a Bool as a Lua boolean.

peekIntegral :: forall a e. (Integral a, Read a) => Peeker e a

Retrieves an Integral value from the Lua stack.

peekRealFloat :: forall a e. (RealFloat a, Read a) => Peeker e a

Retrieve a RealFloat (e.g., Float or Double) from the stack.

Strings

peekByteString :: Peeker e ByteString

Retrieves a ByteString as a raw string.

peekLazyByteString :: Peeker e ByteString

Retrieves a lazy ByteString as a raw string.

peekString :: Peeker e String

Retrieves a String from an UTF-8 encoded Lua string.

peekText :: Peeker e Text

Retrieves a Text value as an UTF-8 encoded string.

peekStringy :: forall a e. IsString a => Peeker e a

Retrieves a String-like value from an UTF-8 encoded Lua string.

This should not be used to peek ByteString values or other values for which construction via fromString can result in loss of information.

peekName :: Peeker e Name

Retrieves a Lua string as Name.

Readable types

peekRead :: forall a e. Read a => Peeker e a

Retrieves a value by getting a String from Lua, then using readMaybe to convert the String into a Haskell value.

Collections

peekKeyValuePairs :: LuaError e => Peeker e a -> Peeker e b -> Peeker e [(a, b)]

Read a table into a list of pairs.

peekList :: forall a e. LuaError e => Peeker e a -> Peeker e [a]

Reads a numerically indexed table t into a list, where the length of the list is equal to rawlen(t). The operation will fail unless all numerical fields between 1 and rawlen(t) can be retrieved.

peekNonEmpty :: LuaError e => Peeker e a -> Peeker e (NonEmpty a)

Like peekList, but fails if the list is empty.

peekMap :: (LuaError e, Ord a) => Peeker e a -> Peeker e b -> Peeker e (Map a b)

Retrieves a key-value Lua table as Map.

peekSet :: (LuaError e, Ord a) => Peeker e a -> Peeker e (Set a)

Retrieves a Set from an idiomatic Lua representation. A set in Lua is idiomatically represented as a table with the elements as keys. Elements with falsy values are omitted.

Combinators

choice :: LuaError e => [Peeker e a] -> Peeker e a

Try all peekers and return the result of the first to succeed.

peekFieldRaw :: LuaError e => Peeker e a -> Name -> Peeker e a

Get value at key from a table.

peekIndexRaw :: LuaError e => Integer -> Peeker e a -> Peeker e a

Get value at integer index key from a table.

peekNilOr

Arguments

:: Alternative m

=> Peeker e a

p

-> Peeker e (m a)

Returns empty if the value at the given index is nil; otherwise returns the result of peeker p.

peekNoneOr

Arguments

:: Alternative m

=> Peeker e a

p

-> Peeker e (m a)

Returns empty if the value at the given index is none; otherwise returns the result of peeker p.

peekNoneOrNilOr

Arguments

:: Alternative m

=> Peeker e a

p

-> Peeker e (m a)

Returns empty if the value at the given index is none or nil; otherwise returns the result of peeker p.

peekPair :: LuaError e => Peeker e a -> Peeker e b -> Peeker e (a, b)

Retrieves a value pair from a table. Expects the values to be stored in a numerically indexed table; does not access metamethods.

peekTriple :: LuaError e => Peeker e a -> Peeker e b -> Peeker e c -> Peeker e (a, b, c)

Retrieves a value triple from a table. Expects the values to be stored in a numerically indexed table, with no metamethods.

Building peek functions

typeChecked

Arguments

:: Name

expected type

-> (StackIndex -> LuaE e Bool)

pre-condition checker

-> Peeker e a

-> Peeker e a

Use test to check whether the value at stack index n has the correct type and use peekfn to convert it to a Haskell value if possible. A successfully received value is wrapped using the Right constructor, while a type mismatch results in Left PeekError with the given error message.

reportValueOnFailure

Arguments

:: Name

expected type

-> (StackIndex -> LuaE e (Maybe a))

-> Peeker e a

Report the expected and actual type of the value under the given index if conversion failed.

typeMismatchMessage

Arguments

:: Name

expected type

-> StackIndex

index of offending value

-> Peek e ByteString

Generate a type mismatch error.