:: Monad m => _ package:base
A special case of
error. It is expected that compilers will
recognize this and insert error messages which are more appropriate to
the context in which
undefined appears.
Calls
perror to indicate that the format string ended early.
Calls
perror to indicate that there is a missing argument in
the argument list.
Calls
perror to indicate that there is a type error or similar
in the given argument.
Used for compiler-generated error message; encoding saves bytes of
string junk.