nocaml.com

Nocaml

Nocaml is a compiled, nearly pure, functional programming language with a lightweight runtime that includes a precise compacting garbage collector. Nocaml is well-suited to use in embedded systems by virtue of having a very small and space-efficient runtime.

Nocaml’s reference compiler is implemented in Ruby, and it can convert a Nocaml program into C code for efficient execution. Nocaml also supports strong static type checking by conversion to OCaml.

Performance

Since it compiles to C, Nocaml achieves superior performance to typical interpreted runtimes for embedded systems. Granted, Nocaml is currently somewhat slower than OCaml (when both are compiled to native code). Below is a comparison of the performance relative to OCaml on a basic non-mutating list-based quicksort program:

The OCaml code was run with OCAMLRUNPARAM=h=201326592,o=4000 to completely remove GC memory pressure during the computation. Instead, a GC cycle was forced at the end of the quicksort calculation to mimic Nocaml’s behavior of GCing before returning to native code. For some reason, Nocaml exceeds OCaml performance on two data points. While the rest of the data points are all slower than OCaml, Nocaml manages to stay above 75% of OCaml performance in all cases.

Future work to improve garbage collector performance in Nocaml is planned.

Language features

Nocaml supports:

• ML-like data-types with constructors (currently defined via Ruby code).

• a slight generalization of ML in which objects may be of any constructor of any type. If this is used, strong static type checking is no longer possible.

Nocaml doesn’t support:

• partial function application (the absence of partial function applications is enforceable in the OCaml-based static type check). Naturally, it is possible to define functions that essentially perform partial function application, but they must be used explicitly not implicitly.

• fancy multi-level match as in OCaml. Instead one can switch over the possible constructors for one expression via a case statement.

• macros (but there are plans to allow macros implemented in Ruby as AST transformations).

Platforms

Nocaml supports x86_64 (SYSV calling convention) and 32-bit MIPS (O32 with ABICALLS). Support for additional platforms is relatively easy to add – there are just two simple functions that need to be written in assembly.

Principle of operation

You may be wondering, how is Nocaml able to do precise garbage collection on a C program? The trick is that the C code output by Nocaml manipulates only pointers, not arbitrary integer values. Thus a stack location that has a value that appears to point into the heap can be assumed to actually be a pointer and subject to adjustment if the heap object it points to is relocated. Actually, “small” integer values and pointers into static memory are also manipulated but these are thankfully not problematic. The drawback to this approach is that it is only possible to manipulate integers through builtins via function calls that cannot be inlined.

License and source code

Nocaml is made available under the terms of the MIT license. The source code for the project is hosted on Github, click here to access it.

More info

Check out the FAQ and the QuickStart pages.