:: String -> Maybe Int -package:universum

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

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.

Throw an error, escaping the current computation up to the nearest catchError (if any).

runThrow (throwError e >>= k) = runThrow (throwError e)