The grab package

newtype Grab bag residue log desideratum =
  Grab
    (bag -> (residue, log, Maybe desideratum))

A Grab:

1. Consumes some portion (none, part, or all) of its input bag;
2. Returns a Result:
   • A residue consisting of the unconsumed input;
   • Some monoidal log e.g. a list of error messages;
   • Some desideratum (the object of desire) produced from the consumed input, or Nothing if the grab failed.

Read more in the Control.Grab module.

The grab-form package

Utilizes the grab package to consume typical HTTP form submission data.

Read more in the tutorial test module.