On 23 January 2013 08:04, John Wiegley
monad-bool implements a pair of Boolean monoids and monads, to support short-circuiting, value-returning computations similar to what Python and Ruby offer with their native && and || operators. ... Use 'onlyIf' with AndM and AndMT to guard later statements, which are only evaluated if every preceding 'onlyIf' evaluates to True. For example:
foo :: AndM Int foo = do onlyIf (True == True) return 100 onlyIf (True == True) return 150 onlyIf (True == False) return 200
When run with `evalAndM foo (-1)` (where (-1) provides a default value), 'foo' returns 150.
Use 'endIf' with OrM and OrMT to chain statements, which are only executed if every preceding 'endIf' evaluated to False. For example:
bar :: OrM Int bar = do endIf (True == False) return 100 endIf (True == False) return 150 endIf (True == True) return 200
John, these sound powerful, but how would I do something esoteric like if/elseIf/endIf ? Conrad.