Cheng Shao TerrorJack

Reader Macros in Common Lisp

This post also appears on lisper.in.

Reader macros are perhaps not as famous as ordinary macros. While macros are a great way to create your own DSL, reader macros provide even greater flexibility by allowing you to create entirely new syntax on top of Lisp.

Paul Graham explains them very well in [On Lisp][] (Chapter 17, Read-Macros):

The three big moments in a Lisp expression's life are read-time, compile-time, and runtime. Functions are in control at runtime. Macros give us a chance to perform transformations on programs at compile-time. ...read-macros... do their work at read-time.

Reddit discussion.

Disclaimer 1: Type classes are great but they are not the right tool for every job. Enjoy some balance and balance to your balance.

Disclaimer 2: I should tidy this up but probably won’t.

Disclaimer 3: Yeah called it, better to be realistic.

Type classes are a language of their own, this is an attempt to document features and give a name to them.

Garbage collection with zero cost at non-GC time

Every once in a while I investigate low-level backend options for PL-s, although so far I haven't actually written any such backend for my projects. Recently I've been looking at precise garbage collection in popular backends, and I've been (like on previous occasions) annoyed by limitations and compromises.

I was compelled to think about a system which accommodates precise relocating GC as much as possible. In one extreme configuration, described in this note, there

	FROM rust:alpine

	RUN apk add --no-cache \
	bash \
	binutils-gold \
	ca-certificates \
	clang \
	curl \
	g++ \
	git \

	# Building musl
	$ ./configure CC=clang LD=lld
	$ make -j72

	# Building with musl (non-lto, no patch)
	$ clang hello.c -nostdlib -fuse-ld=lld -L lib -lc -static lib/crt1.o

	# Building against musl LTO
	$ clang hello.c -nostdlib -fuse-ld=lld -static lib/crt1.o -Wl,--whole-archive lib/libc.a -Wl,--no-whole-archive -Wl,--gc-sections