docs: archive the frozen stage code as one compressed tarball

docs/history kept six stages with a full copy of the project under code/,
3.8 mb of sources duplicated from stage to stage and already superseded. store
them as docs/history/code-snapshots.tar.gz, 0.66 mb, and extract one in place
to read it. every stage's notes.md stays browsable, and the index says where the
code went and how to get it back.

the top-level README points at the archive too. its other two links into
docs/history, 21-micro and 35-bench, were notes that were never kept and do not
resolve; the index now records that.

1 files changed, 0 insertions, 53 deletions

diff --git a/docs/history/15-o3/code/examples/lang.zc b/docs/history/15-o3/code/examples/lang.zc
deleted file mode 100644
index e4d91c5..0000000
--- a/docs/history/15-o3/code/examples/lang.zc
+++ /dev/null
@@ -1,53 +0,0 @@
-// growing the language from inside a program, while it compiles
-
-// x |> f calls f(x). on a stack machine that's just "call": the value is
-// already on the stack, under f's address.
-immediate fn pipe_op() { next(); add_binop("|>", 1, "c"); return 0; }
-pipe_op
-
-// unless (c) stmt
-immediate fn unless()
-{
-	let a;
-	next(); expect(intern("(")); plainuse(expr()); rval(); expect(intern(")"));
-	emitseq(useq[0], ulen[0]);		// not
-	a = hole(); op(O_JZ);
-	substmt();
-	setlit(a, here);
-	return 0;
-}
-// assert (c): the failure message carries the line it was written on
-fn assert_fail(int line) { puts("assertion failed on line "); putn(line); putc(10); halt(); return 0; }
-immediate fn assert()
-{
-	let a, l = tline;
-	next(); expect(intern("(")); plainuse(expr()); rval(); expect(intern(")"));
-	emitseq(useq[0], ulen[0]);		// not: the jump below skips the failure when it holds
-	a = hole(); op(O_JZ);
-	lit(l); callname(intern("assert_fail")); op(O_DROP);
-	setlit(a, here);
-	return 0;
-}
-// times N { body }: the body pasted N times, at compile time
-immediate fn times()
-{
-	let n, b, i = 0;
-	next(); n = tv; next();
-	b = grab();
-	while (i < n) { feed(qdup(b)); i++; }
-	free(d*b);
-	return 0;
-}
-
-fn double(x) { return x * 2; }
-fn inc(x) { return x + 1; }
-fn main()
-{
-	putn(5 |> double |> inc |> double); putc(10);
-	unless (1 > 2) puts("one isn't bigger than two\n");
-	times 3 { putc('*'); }
-	putc(10);
-	assert(double(4) == 8);
-	assert(inc(1) == 3);
-	return 0;
-}