# history

the scrapbook. one folder per stage, each with notes.md: what was asked, what got built, and the working notes from the time, kept as written and only added to. stages that still have their code keep a frozen copy in code/. those six code folders are stored compressed, as `code-snapshots.tar.gz` alongside this file, so that the notes stay browsable without 3.8 mb of duplicated sources in the tree. to read one, extract it in place:

```
tar -xzf code-snapshots.tar.gz 17-o3-boundaries
```

the archive holds `07-zygote`, `10-zc`, `11-types-enhancements`, `13-gap-fixes`, `15-o3` and `17-o3-boundaries`. extracting into this directory restores them; nothing else in the folder is affected. `docs/history/21-micro` and `docs/history/35-bench` are linked from the top-level README but were never kept, notes only, so neither resolves here.

- 01-golf, 02-hardware, 04-darwin-compiler, 05-hybrid, 06-choosing: notes only, their code wasn't kept
- 07-zygote: notes and code (the asm genome and the arm64-only core, as packed in stages 8 and 9)
- 08-packaging: notes only
- 10-zc: notes and code (zc, u m d, the collector, the self-hosting compiler)
- 11-types-enhancements: notes and code (types, generics, reflection, the typechecker, virtual enhancements, the llvm backend)
- 13-gap-fixes: notes and code (joins with fixup frees, the buddy heap, stack checks, error recovery, the prescan, ?: and switch)
- 15-o3: notes and code (the examples, c-style return types, growable and fixed arrays, the o3 optimizing tier, literal-specialized enhancements, the release fix)
- 17-o3-boundaries: notes and code (generics after the name, fattening o3 data on the way out, registers by scope, cached fixed arrays)
- 18-aliases: notes only (borrowed-from marks on derived pointers, quarantine on free)
- 19-tools: notes only (memory debug, do/while, enum, casts, include, syscalls, lib/std.zc)
- 20-words: notes only (the vm word widened from 32 bits to 64)
- 21-micro: notes only (a portable microcore for the same genome)
- 22-size: notes only (a build-time memory map, a 1.31 mb compiler, a 256 kb run-only image)
- 23-baremetal: notes only (the microcore booting on qemu-system, riscv and aarch64 virt, UART in and out)
- 24-backends: notes only (the arm64 jit under qemu-user, and the llvm backend, run against the interpreter)
- 25-genmap: notes only (one layout for every memory size)
- 26-bareapi: notes only (syscall gate on the virt boards: console, clock, exit, files)
- 27-float: notes only (IEEE binary64 on the interpreter, both jits, the microcore and both virt boards)
- 28-bytes: notes only (byte addresses beside word addresses, opcodes 612..617)
- 29-strings: notes only (packed byte strings, `b"..."`, length, slice, concat, and byte syscalls)
- 30-sharing: notes only (shared cons cells and strings, collected by the existing sweep)
- 31-fpu: notes only (hardware float ops where an FPU exists, and a soft-float fallback)
- 32-ftype: notes only (float is a type: calls, globals, fields, parameters, returns; -0.0 is false; 1.field is a field)
- 33-fo3: notes only (o3 lifts float ops: IEEE-safe folds, FP registers, no x-x rewrite)
- 34-ftext: notes only (libc-free print and parse of the full double range)
- 35-bench: notes only (a word sieve and a binary tree, timed against C)
- 36-alloc: notes only (recycle onto the size-class list, a 5-word header, a bump arena)
- 37-call: notes only (o3 calls o3 by entering the region, and fatten only at a real boundary)
- 38-bounds: notes only (a proved index stays in a register, and a +1 loop drops the check)
- 39-blocks: notes only (empty jumps folded, a straight loop rotated to one block)
- 40-fatten: notes only (typed new stamps the header, and a child store writes the owner in the region)
- 41-obytes: notes only (ld8 through st32 lift inside an o3 region)
- 42-roots: notes only (the collector marks from the live stack index, and scrub clears the rest)
- 43-stdlib: notes only (u, m and d are names, an arena and a packed byte buffer, and untyped new inside o3 is zeroed)
- 44-check-mode: notes only (the language server is the compiler in check mode, struct methods and closures, postfix pointer types, same-line braces, a webassembly build)
- 45-fast-alloc: notes only (no prefix pointers, constant-size allocation fast path, maps sized to their program, a makefile, the core sources formatted and explained)
- 46-c-abi: notes only (the backtick is lexical, a parse word must read, lexer speed-ups, llvm target info, extern and cfunc native calls, a default map with a bigger genome slot)
- 47-limits: notes only (a heap that grows to the host's memory, host fill/copy/scan, native calls the optimizer sees, sized integers and f32 with packed arrays, ctz popcnt bswap rotl rotr f2s s2f)

the code folders are snapshots. they're not built or tested from here, the top level is the live tree. the six that survived are in `code-snapshots.tar.gz`, described above.
- 48 landing: packed fields, []sized, f32 extern, page-indexed invalidation, llvm trackers, faster o3 calls
- 49 generics: monomorphized multi-parameter generics and generic methods, llvm inline calls, global const-prop in o3, bigger default map
- 50 adt: tagged enums with fields, constructors, `case member(a, b):` matching, and a coverage warning
- 51 llvm-inline-stdlib: llvm inlining of o3 calls, stdlib text and num helpers, host syscalls through SYS_RAW, and the fuzz campaign's findings
- 52 closures: closure calls work (the block is never run; a call into a heap closure goes through its entry word), captures chain through enclosing closures, and the closure test joins the suite
- 53 typed source: every function, local and global in the compiler, the runtime and the language server is typed (zc0's image does not change), and the extension caches diagnostics by a sha256 of the tree they cover