:: String -> Maybe Int

Read a positive Int, accounting for overflow

Parse seed argument

>>> parseSeed "--seed=6"
Just 6

>>> parseSeed "--seeeed=6"
Nothing

Parse number of threads argument

>>> parseThreads "-j6"
Just 6

>>> parseThreads "-j-2"
Nothing

>>> parseThreads "-jA"
Nothing

Returns the operator precedence of an infix string.

> outernmostPrec "1 + 2"
Just 6

Lookup a terminal capability that has an integer value

Convert to an Int.

throws ExpectFailed. This is nice for writing your own abstractions.

A convenience function for throwing a user error. This is useful for cases where it would be too high a burden to define your own exception type. This throws an exception of type StringException. When GHC supports it (base 4.9 and GHC 8.0 and onward), it includes a call stack.

Lifted throwErrno.

Lifted version of die.

>>> die "Goodbye!"
Goodbye!
*** Exception: ExitFailure 1

Lifted version of die. die is available since base-4.8, but it's more convenient to redefine it instead of using CPP.

When you encounter an error where the only sane way to handle it is to write an error to the log and die messily, use fatalError. This is a good candidate for things like not being able to find configuration files on startup.

General-purpose function to throw a test exception with a String.

Throws a Pending exception with a message to add additional details.

Just like expectationFailure, but does not force the return type to unit. Lifted version of assertFailure

Fail with a message. This operation is not part of the mathematical definition of a monad, but is invoked on pattern-match failure in a do expression. As part of the MonadFail proposal (MFP), this function is moved to its own class MonadFail (see Control.Monad.Fail for more details). The definition here will be removed in a future release.

The type-safe cast operation

Cast a value to a different type. Essentially this is just a drop-in replacement for cast.