@node Overview
@chapter Overview

@command{libhaiku} is a simply error message printing C library
with a collection of haiku that it prints instead of traditional
error messages.

A known issue is that must of the haiku uses 5--7--5@tie{}syllables
rather than 5--7--5@tie{}morae. This is however of lesser importance,
as it is much harder to write a 5--7--5@tie{}mora haiku than a
5--7--5@tie{}syllable haiku.

To use @command{libhaiku} include the head file @file{<libhaiku.h>}
and link with @option{-lhaiku}. The function
@example
void libhaiku_perror(const char* s);
@end example
is used to print the error
messages. @code{libhaiku_perror} shall print an error message in the
format of a haiku, appropriate for the current value of @code{errno}.
If there is not haiku available for the current value of @code{errno},
@code{libhaiku_perror} shall call @code{perror} with @code{s} as its
argument unless @code{s} is @code{NULL}, and then print a generic haiku.

Unlike @code{perror}, @code{libhaiku_perror} shall not print anything
if @code{errno} is zero. If you rather it did, you can use the macro

@example
#define libhaiku_perror(s)       \
  do @{                           \
    const char *s__ = (s);       \
    if (errno && s__)            \
      perror(s__);               \
    errno = errno ? errno : -1;  \
    libhaiku_perror(0);          \
  @} while (0)
@end example