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for-each: operate on runes of a string rather than bytes

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# StreetLISP

	< cinap_lenrek> maybe thats all you need
	< cinap_lenrek> a street lisp
	< cinap_lenrek> sl(1)

[![builds.sr.ht status](https://builds.sr.ht/~ft/sl/commits/main/.build.yml.svg)](https://builds.sr.ht/~ft/sl/commits/main/.build.yml?)

[Coverage report](https://ftrv.se/_/sl/index.html)

A compact interpreter for a minimal lisp/scheme dialect. A street lisp.

This is a reanimation of
https://github.com/lambdaconservatory/femtolisp with bigger plans.

Supported OS: [9front](http://9front.org), Unix-like operating systems (OpenBSD, NetBSD, Linux, etc).

Supported CPUs: any decent 32 or 64-bit, little or big endian.

Regularly tested on: 9front, OpenBSD, NetBSD, Alpine, Android.

Also runs on: MacOS 4.x-9.x, Mac OS X, Haiku, DOS.

Some of the changes from the original include:

 * aggressive clean up, removal, renaming and refactoring
 * bignums
 * previously available (but not merged) patches from the community and [Julia](https://github.com/JuliaLang/julia) are applied
 * `[` and `]`, `{` and `}` are synonyms to `(` and `)`
 * `«` and `»` for verbatim strings
 * `define` → `def`, `define-macro` → `defmacro`
 * `λ` as a shorthand for `lambda`
 * `T` instead of `#t`/`#T` and `NIL` instead of `#f`
 * `c***r` of empty list returns empty list
 * docstrings - `(def (f ...) "Docs here" ...)` and `(help ...)`
 * automatic gensyms for macros (`blah#`) at read time
 * proper `(void)` and `void?`
 * better error reporting - disassembly at the current instruction, location of syntax errors
 * "boot" image is built into the executable
 * vm opcode definitions and tables are generated from a single file

Two ways to learn about more changes:

 * https://todo.sr.ht/~ft/sl?search=status:closed
 * https://git.sr.ht/~ft/sl/log

## Building

### POSIX

	meson setup build -Dbuildtype=release
	ninja -C build test

### Plan 9

	mk all test

### MacOS 4.x-9.x (m68k or PowerPC)

Clone and build [Retro68](https://git.sr.ht/~ft/retro68). This fork grabs the
necessary patches for more things to work as expected:

	git clone https://git.sr.ht/~ft/retro68
	mkdir retro68-build
	cd retro68-build
	../retro68/build-toolchain.bash --ninja
	# wait until everything builds, make sure it did not error out

Now build `sl`:

	cd sl
	export PATH="$PATH:$(pwd)/../retro68-build/toolchain/bin"
	# for PowerPC:
	meson setup build . -Dbuildtype=minsize --cross-file cross/powerpc-apple.txt
	# for m68k:
	meson setup build . -Dbuildtype=minsize --cross-file cross/m68k-apple.txt
	ninja -C build

Either `build/sl.dsk` or `build/sl.bin` is the file to get on your Mac.

NOTE: this isn't a full-fledged port and is going to stay low priority unless somebody
wants to spend time polishing it.

### DOS

Build DJGPP cross-compiler, then:

	export PATH=$PATH:path-to-djgpp-toolchain/bin
	meson setup build . -Dbuildtype=minsize --cross-file cross/djgpp.txt
	ninja -C build

Result is `build/sl.exe`.

## Characteristics

  * lexical scope, lisp-1
  * unrestricted macros
  * case-sensitive
  * simple compacting copying garbage collector
  * Scheme-style varargs (dotted formal argument lists)
  * "human-readable" bytecode with self-hosted compiler
  * circular structure can be printed and read
  * `#.` read macro for eval-when-read and readably printing builtins
  * read macros for backquote
  * symbol character-escaping printer
  * exceptions
  * gensyms (can be usefully read back in, too)
  * `#| multiline comments |#`, `#;(block comment...`, lots of other lexical syntax
  * generic compare function, cyclic equal
  * cvalues system providing C data types ~~and a C FFI~~
  * constructor notation for nicely printing arbitrary values