deck

Minimalistic concatenative language with unstructured control flow that compiles to x86-64 assembly. The Deck runtime currently assumes that it's running under Linux and so tries to use Linux specific systerm calls.

The current compiler uses Bash to tokenise the input stream and recognise some special tokens like labels or functions. NASM is used both as a macro preprocessor and the code generator. This version of the compiler mostly serves as a very rough testbed for ideas and philosophy. A new version of the compiler is being worked on in C++ which should hopefully be far more ergonomic to use than a cobbled together shell script.

You can check out the C++ rewrite in the cdeck directory.

Examples

Some of these examples require functions defined in the prelude.

Factorial

5 fact io_intln sys_ok
@fact >| dup 1 = &.end if dup -- fact * @.end |> .

Sum & Product

[ 1 2 3 4 5 sum ] io_intln
[ 1 2 3 4 5 product ] io_intln
sys_ok

@sum &+ swp &reduce .
@product &* swp &reduce .

Min/Max

11 23 max io_intln
64 73 min io_intln
sys_ok
@min >| dupp > rotr ? ret #! ( a b cont -> q )
@max >| dupp < rotr ? ret #! ( a b cont -> q )

Design & Rationale

Deck is an exercise in minimalism and so constructs common in more mainstream languages are entirely missing from Deck.

The most obvious example is structured control flow. It has long been considered that unstructured control flow is "harmful" after Edsgar Dijkstra published his "Go To Statement Considered Harmful" letter. Due to this, Deck has no concept of for-loops, while-loops or if-else branches. All we have to use is the choice operator (?) which collapses to one of two values based on a flag condition and labels aswell as functions. Classical loops and branching can be emulated by building abstractions on top of the choice operators, labels and functions.

Deck also has no concept of types, less so than even a dynamically typed language. Everything in Deck is normally considered to be a signed integer unless the operator decides to cast it to some other type (i.e. a pointer). As with everything else in Deck, this has potential for bugs but also gives you plenty of control.

One of the nice things that comes along with the lack of types is a runtime determined stack size which allows you to do some fun things like push a variable number of values to the stack based on a runtime value. This is usually not possible in most languages unless you make use of heap allocated memory but that incurs a runtime cost and is not as ergonomic to use.

The return address is passed to functions explicitly which allows the user to decide where it goes or what to do with it. You can pop the return address, push it to the other side of the deque or just leave it on the stack and juggle it around. It's also possible to call a function without pushing the return address using the go operator (.) if you want to try doing direct threading or "computed goto".

Goals

• Register Allocation
• Function Inlining
• Constant Folding
• C++ Rewrite (check the cdeck directory)

Requirements

• NASM
• Bash
• ld (GNU Linker)
• m4 (Macro Processor)

Build & Run

To run the compiler you simply have to pipe your source file into the compiler script (dcc) like so:

$ ./dcc bin < main.dk
$ ./bin

This will spit out a compiled ELF64 binary with the name bin in the local directory.

Resources

Code Generation

• https://blog.rchapman.org/posts/Linux_System_Call_Table_for_x86_64/
• https://www.nasm.us/xdoc/2.13.03/html/nasmdoc0.html
• https://www.felixcloutier.com/x86/
• https://arxiv.org/pdf/2011.05608v1.pdf
• https://legacy.cs.indiana.edu/~dyb/pubs/ddcg.pdf
• https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.156.2546&rep=rep1&type=pdf
• https://bernsteinbear.com/assets/img/46b-codegeneration-in-V8.pdf
• https://www.microsoft.com/en-us/research/wp-content/uploads/2016/11/dps-fhpc17.pdf
• https://www.golfscript.com/golfscript/builtin.html

Unicode

• https://lexy.foonathan.net/reference/dsl/unicode/
• https://github.com/foonathan/lexy/blob/5928c5644eec6ddf308a3b3df93259bf44dc9eb1/include/lexy/code_point.hpp
• https://here-be-braces.com/fast-lookup-of-unicode-properties/
• https://gitlab.com/be-sc/unicode_algorithm/-/blob/master/tools/generate_lookup_tables.py
• https://www.strchr.com/multi-stage_tables

License

This project uses the GPL-3.0 license. (check LICENSE)