flesh/Readme.org

#+Title: Relish: Rusty Expressive LIsp SHell
#+Author: Ava Hahn

Note: this document is best read within a dedicated ORG mode interpreter

* Purpose statement
The purpose of Relish is to create a highly expressive POSIX shell using a lisp interpreter.

* Goals
- Iterate on the ideas and designs that were tested with SHS
https://gitlab.com/whom/shs
- Act as both a high level scripting language and as a system shell
- To be as portable as possible
- To provide code and framework that can be embedded in other applications needing a user facing interpreter
- To be well tested code
- No unsafe code without extreme consideration and rigorous containment

* Contact
- Matrix chat: #vomitorium:matrix.sunnypup.io
https://matrix.to/#/#vomitorium:matrix.sunnypup.io

* How to use
** Configuration
By default Relish will read from ~/.relishrc for configuration, but the default shell will also accept a filename from the RELISH_CFG_FILE environment variable.

*** The configuration file
The configuration file is a script containing arbitrary Relish code.
On start, any shell which leverages the configuration code in the config module (file:src/config.rs) will create a clean seperate context, including default configuration values, within which the standard library will be initialized.
The configuration file is evaluated and run as a standalone script and may include arbitrary executable code. Afterwards, configuration values found in the variable map will be used to configure the standard library function mappings that the shell will use.
Errors during configuration are non-terminal and will result in default values being returned.

**** Important points to note
- When the configuration file is run, it will be run with default configuration values.
- The user/script interpreter will be run with a *re-instantiation* of the standard library, using the previously defined configuration variables.
- Variables and functions defined during configuration will carry over to the user/script interpreter, allowing the user to load any number of custom functions and variables.

*** Configuration Values
- CFG_RELISH_POSIX (default 0): when on, enables POSIX style job control.
- CFG_RELISH_ENV (default 1): when on, interpreter's variable table and environment variable table are kept in sync.
- CFG_RELISH_PROMPT (default (echo "λ ")): A *function* definition which is called in order to output the prompt for each loop of the REPL.
Note: CFG_RELISH_PROMPT is only loaded once and will be ignored after initial configuration.

** Compilation 
#+BEGIN_SRC sh
  cargo build
#+END_SRC

** Testing
#+BEGIN_SRC sh
  cargo test
#+END_SRC

** Running (the main shell)
#+BEGIN_SRC sh
  cargo run src/bin/main.rs
#+END_SRC

* Guide to codebase
** file:tests directory
Start here if you are new.
Most of these files have unimplemented tests commented out in them.
Contributions that help fill out all of these tests
*** Eval tests: file:tests/test_eval.rs
These are particularly easy to read and write tests.

*** Func tests: file:tests/test_func.rs
You can consider these to extend the eval tests to cover the co-recursive nature between eval and func calls.

*** Lex tests: file:tests/test_lex.rs
These tests verify the handling of syntax.

*** Lib tests: (tests/test_lib*)
These tests are unique per stdlib module.

** file:src directory
This directory contains all of the user facing code in relish.
Just a few entries of note:
*** segment: file:src/segment.rs
This file lays out the +spiritual+ +theological+ +ideological+ +theoretical+ mechanical underpinnings of the entire interpreter.
The entire LISP machine centers around a singlet or pairing of datum.
The ~Ctr~ datatype provides an abstraction for which any type of data, including a ~Seg~ can be a datum.
The ~Seg~ datatype provides a mechanism to hold a single datum or a pair of datum. It is implemented as two ~Ctr~s: ~car~ and ~cdr~.
A primitive type system is provided through the Rust Enum datatype. A number of utility functions follow.

*** lib: file:src/lib.rs
This defines a library that can be included to provide an interpreter interface within any Rust project.
It includes the core interpreter mechanisms, full stdlib, and the configuration system.
Your project can use or not use any number of these components. They can certainly be used to support language development for other LISP machines,
or even other languages.

*** stl: file:src/stl.rs
This defines the ~get_stdlib~ function.
This function takes in a Variable Table (likely containing custom configuration) and returns a Function Table for use in an interpreter.
Any new addition to the stdlib must make its way here to be included in the main shell (and any other shell using the included ~get_stdlib~ function).
You may choose to override this function if you would like to include your own special functions in your own special interpreter, or if you would like to pare down the stdlib to a small minimal subet of what it is.

*** bin: file:src/bin/
This contains any executable target of this project. Notably the main shell file:src/bin/main.rs.


* Current Status / TODO list
Note: this section will not show the status of each item unless you are viewing it with a proper orgmode viewer
*** DONE Core interpreter stuffs
**** DONE Lexing
**** DONE Parsing
**** DONE Evaluation
**** DONE Function table
**** DONE Variable table
*** DONE Echo function
*** DONE Redo segment.rs
**** DONE Clone impl for Ctr
(derived)
**** DONE Derive Clone for Seg
**** DONE ToString impl for Ctr
**** DONE ToString impl for Seg
**** DONE Display, Debug impls for Ctr
**** DONE Derive Display, Debug for Seg
**** DONE Default impl for Ctr
**** DONE Derive Default for Seg
**** WONTDO From/Into for Ctr
**** DONE Iterator for Seg
**** WONTDO Consider RefCell for tables, or using 'static lifetime
one of these may fix borrow checker insanity
**** DONE make FTable and VTable singleton modules (global mutable)
**** WONTDO make FTable and VTable into private definitions
**** DONE YEET AST EVERYWHERE. PASS AROUND A SEG REF.
*** TODO refactor code into more digestible, better organized pieces
**** DONE combine var and func table into global sym table
**** DONE refactor and reimplement eval
**** TODO (test and get it working)
**** TODO lex/eval/e2e tests for var that holds callback func
*** TODO Rudimentary Control Flow
**** TODO if clause
**** TODO loop clause
**** TODO while clause
**** TODO circuit clause
*** DONE Configuration
**** DONE Function to load configuration into Variable and Function tables
**** DONE Configure in main shell
**** DONE manual verification of config settings
**** DONE manual verification of config defaults
*** TODO Help function
*** TODO Env function
*** DONE User variable declaration
*** DONE User function declaration
*** TODO Load (load a script) function
Pull/Refactor the logic out of the configure functions.
Optionally return a list of new variables and/or functions?
Will need a concatenate function for func tables
*** TODO Main shell calls Load function on arg and exits
*** TODO Custom error printing
*** TODO Custom ast pretty print
*** DONE Implement Ctr, Ast to_string / Display trait
*** TODO get_stdlibphase1 -> configuration -> get_stdlibphase2
*** TODO STDLIB
*** TODO Shell module
**** TODO Process launching with environment variables
**** TODO Foreground process TTY
**** TODO Background processes
**** DONE append
**** TODO string operations
***** DONE concatenate
***** TODO substr by index
***** TODO tokenize by delimiter
***** TODO sprintf / string build
**** TODO arithmetic operations
***** TODO
**** TODO Serialize/Deserialize basic data types
**** TODO file opterations
***** TODO
**** TODO Network library
***** TODO HTTP Client
***** TODO TCP Stream client
***** TODO UDP Client
***** TODO TCP Listener
***** TODO HTTP Listener
***** TODO UDP Listener
*** TODO Ensure full test coverage
**** TODO Implement missing func, Lex, Eval tests
**** TODO stdlib tests :)