happy - the parser generator for Haskell
happy [OPTION]... file [OPTION]...
This manual page documents briefly the happy command.
This manual page was written for the Debian GNU/Linux distribution
because the original program does not have a manual page. Instead, it
has documentation in various other formats, including DVI, Info and
HTML; see below.
Happy is a parser generator system for Haskell. ‘HAPPY’ is a dyslexic
acronym for ‘A Yacc-like Haskell Parser generator’.
There are two types of grammar files, file.y and file.ly, with the
latter observing the reverse comment bird track convention (i.e. each
code line must begin with ‘>’). The examples distributed with Happy
are all of the .ly form.
Caveat: When using hbc (Chalmers Haskell) the command argument
structure is slightly different. This is because the hbc run time
system takes some flags as its own (for setting things like the heap
size, etc). This problem can be circumvented by adding a single dash
(‘-’) to your command line. So when using a hbc generated version of
Happy, the argument structure is:
happy - [OPTION]... file [OPTION]...
The programs follow the usual GNU command line syntax, with long
options starting with two dashes (‘--’). A summary of options is
included below. For a complete description, see the other
Show summary of options.
Print version information on standard output then exit
Instructs Happy to generate a parser using an array-based shift
reduce parser. When used in conjunction with -g, the arrays
will be encoded as strings, resulting in faster parsers.
Without -g, standard Haskell arrays will be used.
Instructs Happy to generate a parser that uses GHC-specific
extensions to obtain faster code.
Use GHC’s unsafeCoerce# extension to generate smaller faster
parsers. One drawback is that some type safety is lost, which
means that a parser generated with -c may compile fine but crash
at run-time. Be sure to compile your grammar without -c first
to ensure it is type-correct.
This option has quite a significant effect on the performance of
the resulting parser, but remember that parsers generated this
way can only be compiled by GHC 3.02 and above.
This option may only be used in conjuction with -g.
Generate a parser that will print debugging information to
stderr at run-time, including all the shifts, reductions, state
transitions and token inputs performed by the parser.
This option may only be used in conjuction with -a.
-i [FILE], --info[=FILE]
Directs Happy to produce an info file containing detailed
information about the grammar, parser states, parser actions,
and conflicts. Info files are vital during the debugging of
The filename argument is optional, and if omitted the info file
will be written to FILE.info (where FILE is the input file name
with any extension removed).
-o FILE, --outfile=FILE
Specifies the destination of the generated parser module. If
omitted, the parser will be placed in FILE.hs, where FILE is the
name of the input file with any extension removed. If FILE is -
the generated parser is sent to the standard output.
-m NAME, --magic-name=NAME
Happy prefixes all the symbols it uses internally with either
happy or Happy. To use a different string, for example if the
use of happy is conflicting with one of your own functions,
specify the prefix using the -m option.
-t DIR, --template=DIR
Instructs Happy to use this directory when looking for template
files: these files contain the static code that Happy includes
in every generated parser. You shouldn’t need to use this
option if Happy is properly configured for your computer.
Instructs Happy to output a GLR parser instead of an LALR(1)
Causes the GLR parser to generate code for decoding the parse
forest to a list of semantic results (requires --ghc).
Causes the GLR parser to filter out nodes which aren’t required
for the semantic results (an experimental optimisation, requires
/usr/share/doc/happy, the Happy homepage (http://haskell.org/happy/)
Happy Version 1.18.4
Copyright (c) 1993-1996 Andy Gill, Simon Marlow; (c) 1997-2001 Simon
This manual page was written by Michael Weber <firstname.lastname@example.org>,
for the Debian GNU/Linux system (but may be used by others).