oplang

OpLang is a stack-based esoteric programming language based on Brainfuck.

Installing

The compiler is available on Hackage, and can be installed via cabal (which can itself be installed via ghcup).

cabal install oplang

Usage

To compile and run an OpLang program, use:

oplang code.op
./code.out

For a list of available command-line options, use oplang --help.

Building from source

Prerequisites:

• GHC >=9.2
• cabal >=3.6

(Both can be installed via ghcup)

To build the project, use cabal build.

To run the project locally (without installing), use cabal run . -- <args>.

Language features

OpLang is a strict superset of Brainfuck.

Its main improvement is the addition of user-defined operators, which are analogous to user-defined functions in languages like C or Python.

The "memory tape" in OpLang is specific to each operator invocation (akin to the stack frames of functions in C), and there is a separate "stack" which persists across operator invocations.

Each cell in the tape(s) and stack is 1 byte, and overflow/underflow is allowed.

The default sizes of the stack and of memory tapes is 4KB. These defaults can be individually modified via command-line arguments.

Syntax

OpLang has 10 built-in operators, 8 of which are the Brainfuck operators, with the same semantics:

• +: Increment the current cell
• -: Decrement the current cell
• <: Move the current cell pointer to the left
• >: Move the current cell pointer to the right
• ,: Read a character from stdin and store its ASCII value in the current cell
• .: Interpret the current cell as an ASCII character and print it to stdout
• [: Begin a loop (i.e. if the value at the current cell is zero, jump to the next ])
• ]: End a loop (i.e. if the value at the current cell is non-zero, jump to the previous [)

And 2 of them are new operators that modify the stack:

• ;: Pop a value from the stack and store it into the current cell
• :: Push the value of the current cell onto the stack

An OpLang program consists of a series of custom operator definitions, followed by the "toplevel" (similar to a main() function in other languages).

An operator definition consists of the operator's name, followed by the operator's body, enclosed in {/}.

Single-line comments are supported, and are introduced by the # character.

Here's a simple program that reads a character from stdin, adds 3 to it, and prints it back:

a { ; +++ : }
,: a ;.

For more example programs, see the examples directory.

Compiler architecture

The compiler works by translating the input OpLang source into C, and then compiling that using the system's C compiler. To use a different C compiler, set the CC environment variable.

The compiler uses an intermediate representation (which can be shown with the --dump-ir option) on which it performs a number of optimizations, generating C code that is much smaller and faster than a direct translation would yield.

License

This repository is licensed under the terms of the GNU General Public License v3.

For more details, see the license file.