Documentation

A basic dependent sum type where the first component is a tag that specifies the type of the second. For example, think of a GADT such as:

data Tag a where
   AString :: Tag String
   AnInt   :: Tag Int
   Rec     :: Tag (DSum Tag Identity)

Then we can write expressions where the RHS of (:=>) has different types depending on the Tag constructor used. Here are some expressions of type DSum Tag Identity:

AString :=> Identity "hello!"
AnInt   :=> Identity 42

Often, the f we choose has an Applicative instance, and we can use the helper function (==>). The following expressions all have the type Applicative f => DSum Tag f:

AString ==> "hello!"
AnInt   ==> 42

We can write functions that consume DSum Tag f values by matching, such as:

toString :: DSum Tag Identity -> String
toString (AString :=> Identity str) = str
toString (AnInt   :=> Identity int) = show int
toString (Rec     :=> Identity sum) = toString sum

The (:=>) constructor and (==>) helper are chosen to resemble the (key => value) construction for dictionary entries in many dynamic languages. The :=> and ==> operators have very low precedence and bind to the right, making repeated use of these operators behave as you'd expect:

-- Parses as: Rec ==> (AnInt ==> (3 + 4))
-- Has type: Applicative f => DSum Tag f
Rec ==> AnInt ==> 3 + 4

The precedence of these operators is just above that of $, so foo bar $ AString ==> "eep" is equivalent to foo bar (AString ==> "eep").

To use the Eq, Ord, Read, and Show instances for DSum tag f, you will need an ArgDict instance for your tag type. Use deriveArgDict from the constraints-extras package to generate this instance.

Convenience helper. Uses pure to lift a into f a.

The Lambdabot entry point. Initialise plugins, connect, and run the bot in the LB monad

Also, handle any fatal exceptions (such as non-recoverable signals), (i.e. print a message and exit). Non-fatal exceptions should be dealt with in the mainLoop or further down.

Priorities are used to define how important a log message is. Users can filter log messages based on priorities.

These have their roots on the traditional syslog system. The standard definitions are given below, but you are free to interpret them however you like. They are listed here in ascending importance order.