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https://github.com/akabe/evilml
A compiler from ML to C++ template language
https://github.com/akabe/evilml
cpp functional-programming ocaml
Last synced: 9 days ago
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A compiler from ML to C++ template language
- Host: GitHub
- URL: https://github.com/akabe/evilml
- Owner: akabe
- Created: 2015-08-13T06:45:49.000Z (about 9 years ago)
- Default Branch: master
- Last Pushed: 2015-08-27T13:48:59.000Z (about 9 years ago)
- Last Synced: 2024-05-01T13:33:30.449Z (6 months ago)
- Topics: cpp, functional-programming, ocaml
- Language: JavaScript
- Size: 1.57 MB
- Stars: 158
- Watchers: 8
- Forks: 4
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
Evil ML
=======
[](https://travis-ci.org/akabe/evilml)
Evil ML is a joke compiler from ML to **C++ template language**
(not ordinary C++ code). Please, don't use this for practical purposes.
C++ template is a **higher-order pure functional** programming language
traditionally used for **compile-time** computation, while its syntax is
verbose and hard to use.
[ML](https://en.wikipedia.org/wiki/ML_%28programming_language%29),
a higher-order functional programming language, is simple, practical and
easy to understand, so that we jokingly implemented this compiler. You can
easily use black magic in C++ template programming. This will give you nightmares.
P.S. `constexpr` (supported C++11 or above) is useful. Why don't you use it?
Features
--------
- [OCaml](http://ocaml.org)-like higher-order pure functional language
(Hindley-Milner polymorphism, no value restriction).
- Type inference is performed. Most types are automatically inferred.
- Variant types are supported.
- You can write raw C++ code in `(*! ... *)` in top level.
- `#use "foo.ml"` loads .ml files in top level (double semi-colons `;;`
are not needed at the end). The .ml files you can load are found in
directory [evilml/include](https://github.com/akabe/evilml/blob/master/include).
Difference from OCaml:
- Strings have type `char list` (type `string` does not exist).
- Module system and separate compilation are not supported.
- User-defined operators are not allowed.
- `type` keyword in top level can only define *variant types*. You cannot
declare aliases of types and records.
- Pattern match is only performed by `match`. Patterns cannot appear in formal
arguments and l.h.s. of let bindings.
- Exhaustivity checking of pattern matching is not implemented. (future work)
- Identifiers are defined as regular expression `[a-zA-Z_][a-zA-Z0-9_]*`.
Primes cannot be used, and names that begin `__ml_` are
reserved by this compiler. Identifiers of data constructors begin capital
letters.
- Top-level shadowing of identifiers (variables, types, and constructors) is
prohibited.
Install
-------
```
./configure
make
make install
```
Usage
-----
You can compile `foo.ml` as follows:
```
evilml foo.ml
```
Demo: quick sort
----------------
[examples/quicksort/qsort.ml](examples/quicksort/qsort.ml) implements quick sort
of a list of 8 elements. You can compile the ML program into C++ template as
[online demo](http://akabe.github.io/evilml/).
1. Check the check box of "Generate stand-alone code (embedding evilml.hpp)"
2. Push the button "Compile"
3. Copy and paste the generated C++ code into file `qsort.cpp`
4. Try to compile and run it:
```
$ g++ qsort.cpp
$ ./a.out
1 2 3 4 5 6 7 8
```
In order to make sure that sorting is executed in compile time,
we suggest to use `g++ -S qsort.cpp` and open `qsort.s`:
```asm
...
movl $1, 4(%esp) ; pass 1 to printf
movl $.LC0, (%esp)
call printf
movl $2, 4(%esp) ; pass 2 to printf
movl $.LC0, (%esp)
call printf
movl $3, 4(%esp) ; pass 3 to printf
movl $.LC0, (%esp)
call printf
movl $4, 4(%esp) ; pass 4 to printf
movl $.LC0, (%esp)
call printf
movl $5, 4(%esp) ; pass 5 to printf
movl $.LC0, (%esp)
call printf
movl $6, 4(%esp) ; pass 6 to printf
movl $.LC0, (%esp)
call printf
movl $7, 4(%esp) ; pass 7 to printf
movl $.LC0, (%esp)
call printf
movl $8, 4(%esp) ; pass 8 to printf
movl $.LC1, (%esp)
call printf
...
```
(Of course, you can use `std::cout` to print integers in `qsort.cpp`,
however we make use of `printf` for readable assembly code.)
Bugs
----
- `let rec diverge _ = diverge ()` should be infinite loop, but generated C++
code causes compilation error. `let rec diverge n = diverge (n+1)` passes C++
compilation. (I don't know the formal definition of reduction rules of C++
template expressions.)
- C++03 template prohibits operation of float-point values, so that this
compiler outputs wrong code.