try +base
Similar to catch, but returns an Either result which is (Right a) if no exception was raised, or (Left e) if an exception was raised and its value is e.
> try a = catch (Right `liftM` a) (return . Left)
Note: as with catch, it is only polite to use this variant if you intend to re-throw the exception after performing whatever cleanup is needed. Otherwise, tryJust is generally considered to be better.
Also note that System.IO.Error also exports a function called System.IO.Error.try with a similar type to try, except that it catches only the IO and user families of exceptions (as required by the Haskell 98 IO module).
The construct try comp exposes IO errors which occur within a computation, and which are not fully handled.
Non-I/O exceptions are not caught by this variant; to catch all exceptions, use Control.Exception.try from Control.Exception.
Similar to catch, but returns an Either result which is (Right a) if no exception of type e was raised, or (Left ex) if an exception of type e was raised and its value is ex. If any other type of exception is raised than it will be propogated up to the next enclosing exception handler.
> try a = catch (Right `liftM` a) (return . Left)
Note that System.IO.Error also exports a function called System.IO.Error.try with a similar type to Control.Exception.try, except that it catches only the IO and user families of exceptions (as required by the Haskell 98 IO module).
A variant of try that takes an exception predicate to select which exceptions are caught (c.f. catchJust). If the exception does not match the predicate, it is re-thrown.
A variant of try that takes an exception predicate to select which exceptions are caught (c.f. catchJust). If the exception does not match the predicate, it is re-thrown.
A non-blocking version of putMVar. The tryPutMVar function attempts to put the value a into the MVar, returning True if it was successful, or False otherwise.
Throw an IOError corresponding to the current value of getErrno if the IO action returns a result of -1, but retries in case of an interrupted operation.
Throw an IOError corresponding to the current value of getErrno if the IO action returns nullPtr, but retry in case of an interrupted operation.
as throwErrnoIf, but retry the IO action when it yields the error code eINTR - this amounts to the standard retry loop for interrupted POSIX system calls.
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