Requirements
See opam file for version constraints.
optional
Toplevel requirements
- tyxml, reactiveData
- ocp-indent: needed to support indentation in the toplevel
- higlo: needed to support Syntax highlighting in the toplevel
- cohttp: needed to build the toplevel webserver
Installation
Opam
opam install js_of_ocaml js_of_ocaml-compiler js_of_ocaml-ppx
Usage
Your program must first be compiled using the OCaml bytecode compiler ocamlc. JavaScript bindings are provided by the js_of_ocaml package. The syntax extension is provided by js_of_ocaml-ppx package.
ocamlfind ocamlc -package js_of_ocaml -package js_of_ocaml-ppx -linkpkg -o cubes.byte cubes.ml
Then, run the js_of_ocaml compiler to produce JavaScript code:
js_of_ocaml cubes.byte
Features
Most of the OCaml standard library is supported. However,
- Most of the Sys module is not supported.
Extra libraries distributed with OCaml (such as Thread) are not supported in general. However,
- Bigarray: bigarrays are supported using Typed Arrays
- Num: supported
- Str: supported
- Graphics: partially supported using canvas (see js_of_ocaml-lwt.graphics)
- Unix: time related functions are supported
Tail call is not optimized in general. However, mutually recursive functions are optimized:
- self recursive functions (when the tail calls are the function itself) are compiled using a loop.
- trampolines are used otherwise. More about tail call optimization.
Effect handlers are supported with the --enable=effects flag.
Data representation
Data representation differs from the usual one. Most notably, integers are 32 bits (rather than 31 bits or 63 bits), which is their natural size in JavaScript, and floats are not boxed. As a consequence, marshalling, polymorphic comparison, and hashing functions can yield results different from usual:
- marshalling floats might generate different output. Such output should not be unmarshalled using the standard ocaml runtime (native or bytecode).
- the polymorphic hash function will not give the same results on datastructures containing floats;
- these functions may be more prone to stack overflow.
OCaml | javascript |
|---|
int | number (32bit int) |
int32 | number (32bit int) |
nativeint | number (32bit int) |
int64 | Object (MlInt64) |
float | number |
string | string or object (MlBytes) |
bytes | object (MlBytes) |
"immediate" (e.g. true, false, None, ()) | number (32bit int) |
"block" | array with tag as first element (e.g. C(1,2) => [tag,1,2]) |
array | block with tag 0 (e.g. [\|1;2\|] => [0,1,2]) |
tuple | block with tag 0 (e.g. (1,2) => [0,1,2]) |
record | block (e.g. {x=1;y=2} => [0,1,2]) |
constructor with arguments | block (e.g. C (1, 2) => [tag,1,2]) |
module | block |
exception and extensible variant | block or immediate |
function | function |
Toplevel
Contents of the distribution
Filename | Description |
|---|
LICENSE | license and copyright notice |
README | this file |
compiler/ | compiler |
examples/ | small examples |
lib/ | library for interfacing with JavaScript APIs |
ppx/ | ppx syntax extensions |
runtime/ | runtime system |
toplevel/ | web-based OCaml toplevel |
