| Chapter 7 |
The commands camlp4 |
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Camlp4 is a command which you can type from your shell. It has several
versions: camlp4, camlp4o, camlp4r. Actually, the
basic command is camlp4, the other ones being shortcuts for
this command with syntaxes previously loaded (see man page).
Its options are in two parts: the ``load'' options and the ``other''
options. The input file is among the ``other'' options, generally a
.mli interface file or .ml implementation file.
The ``load'' options *must* come first. They are a list of OCaml
object files (cmo) or library file (cma) which are loaded in camlp4
core before any other operation. These files are found in a path. You
can use the option -I to add directories in this path. By
default, the path contains only the camlp4 library directory
(depending on the installation).
Notice that the current directory is *not* by default in the path: to
load a file belonging to the current directory, you have to use either
the option -I . or to type the object file prefixed by a dot
and a slash.
In fact, the command camlp4 alone, without any load option does
nothing with the input file and fails. You need to specify at least
one parser and one printer. If you don't specify any parser, you get
the message ``Failure: no loaded parsing module'', if you don't
specify any printer, ``Failure: no printer''. When it runs,
camlp4 applies the parser to the input file, which builds a
syntax tree and this syntax tree is printed using the printer.
The other options follow. If there is a risk of ambiguities, you can
use -- to separate the load options and the other ones: indeed,
the other options can be extended by the object files loaded in the
core: in particular, the provided object file pr_depend.cmo
adds -I among the other options.
To see the list of available options, type camlp4 -help or, since
the object files can extend the options, type
camlp4 <load-options> -help where <load-options> is
your load options. Type, for example, and compare the results:
camlp4 -help
camlp4 pa_r.cmo pa_extend.cmo -help
camlp4 pr_depend.cmo -help
| 7.3 |
The predefined object files |
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The predefined object files, available in the camlp4 library