utop/README.md

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utop - a universal toplevel for OCaml
=====================================
utop is an improved toplevel for OCaml. It can run in a terminal or
in Emacs. It supports line edition, history, real-time and context
sensitive completion, colors, and more.
It integrates with the tuareg and typerex modes in Emacs.
Installation via opam
---------------------
The easiest and recommended way of installing utop is via
[opam](http://opam.ocamlpro.com/):
$ opam install utop
If you want to build it manually, you should install all the
dependencies listed in the next section.
Dependencies
------------
* [OCaml](http://caml.inria.fr/ocaml/) (>= 3.12)
* [findlib](http://projects.camlcity.org/projects/findlib.html)
* [react](http://erratique.ch/software/react)
* [lwt](http://ocsigen.org/lwt/) (>= 2.4.0) built with react support
* [Camomile](http://github.com/yoriyuki/Camomile) (>= 0.8)
* [zed](http://github.com/diml/zed) (>= 1.2)
* [lambda-term](http://github.com/diml/lambda-term) (>= 1.2)
For building the development version, you also need to install
[oasis](http://oasis.forge.ocamlcore.org/) (>= 0.3.0).
utop also requires OCaml compiler libraries. Since OCaml 4.00 they are
already installed, for previous versions:
* if you are using debian, they are available as the package
ocaml-compiler-libs,
* if you are using godi, they are installed by default,
* if you installed ocaml by hand, you can run the script
`utils/install-compiler-libs.sh`.
Installation from sources
-------------------------
To build and install utop:
$ ./configure
$ make
$ make install
### Documentation and manual pages _(optional)_
To build the documentation:
$ make doc
It will then be installed by `make install`.
### Tests _(optionnal)_
To build and execute tests:
$ ./configure --enable-tests
$ make test
Usage
-----
To use utop, simply run:
$ utop
utop display a bar after the prompt which is used to show possible
completions in real-time. You can navigate in it using `Alt+Left` and
`Alt+Right`, and select one completion using `Alt+Tab`.
Customization
-------------
### Colors
To add colors to utop, copy one of the files `utoprc-dark` or
`utoprc-light` to `~/.utoprc`. `utoprc-dark` is for terminals with
dark colors (such as white on black) and `utoprc-light` is for
terminals with light colors (such as black on white).
### Prompt
You can customize the prompt of utop by setting the reference
`UTop.prompt`.
### Key bindings
Key bindings in the terminal can be changed by writing a
`~/.lambda-term-inputrc` file. For example:
[read-line]
C-left: complete-bar-prev
C-right: complete-bar-next
C-down: complete-bar
If manual pages are correctly installed you can see a description of
this file by executing:
$ man 5 lambda-term-inputrc
Integration with emacs
----------------------
To use utop in emacs, add the following line to your ~/.emacs file:
```scheme
(autoload 'utop "utop" "Toplevel for OCaml" t)
```
Then you can run utop by executing the command `utop` in emacs.
If you installed utop through opam, customize `utop-command` to
`opam config exec "utop -emacs"`.
Integration with the tuareg/typerex mode
----------------------------------------
You can replace the default toplevel used by the tuareg or typerex
mode by utop, for that add the following lines to your `~/.emacs` file:
```scheme
(autoload 'utop-setup-ocaml-buffer "utop" "Toplevel for OCaml" t)
(add-hook 'tuareg-mode-hook 'utop-setup-ocaml-buffer)
(add-hook 'typerex-mode-hook 'utop-setup-ocaml-buffer)
```
You can also complete text in a tuareg or typerex buffer using the
environment of the toplevel. For that bind the function
`utop-edit-complete` to the key you want.
Common error
------------
If you get this error when running utop in a terminal or in emacs this
means that the environment variable `CAML_LD_LIBRARY_PATH` is not set
correctly:
Fatal error: cannot load shared library dlllwt-unix_stubs
Reason: dlopen(dlllwt-unix_stubs.so, 138): image not found
It shall point to the directory `stublibs` inside your ocaml installation.
Creating a custom utop-enabled toplevel
---------------------------------------
If you want to create a custom toplevel with utop instead of the
classic one you need to link it with utop and its dependencies and
call `UTop_main.main` in the last linked unit. You also need to pass
the `-thread` switch when linking the toplevel.
The easiest way to do that is by using ocamlfind:
$ ocamlfind ocamlmktop -o myutop -thread -linkpkg -package utop myutop_main.cmo
Where `myutop_main.ml` contains:
```ocaml
let () = UTop_main.main ()
```
You can also use the `ocamlc` sub-command instead of `ocamlmktop`, in
this case you need to pass these thee extra arguments:
* `-linkall` to be sure all units are linked into the produced toplevel
* `-package compiler-libs.toplevel`
* `-predicates create_toploop`
With the last option ocamlfind will generate a small ocaml unit,
linked just before `myutop_main.cmo`, which will register at startup
packages already linked in the toplevel so they are not loaded again
by the `#require` directive. It does the same with the `ocamlmktop`
sub-command.
For example:
$ camlfind ocamlc -o myutop -thread -linkpkg -linkall -predicates create_toploop \
-package compiler-libs.toplevel,utop myutop.cmo
Note that if you are not using ocamlfind, you will need to do that
yourself. You have to call `Topfind.don't_load` with the list of all
packages linked with the toplevel.
A full example using ocamlbuild is provided in the
[examples/custom-utop]() directory.