path: root/docs/history/10-zc/code/src/compiler.zc

// ============================================================================
// compiler.zc: the resident zc compiler. it lives in the genome next to the
// runtime, compiles source straight to vm words in memory, and is visible to
// the programs it compiles: every function and global here can be called or
// patched by name, and parse words (immediate fns) run inside it.
// ============================================================================

// ---- compiler data region (fixed addresses, 0xA0100 .. 0xBE100) ----
const IHN = 8192;
const R_IH = 0xA0100;		// intern hash table
const R_POOL = 0xA2100;		// interned strings: [symbol head] chars 0
const R_POOLEND = 0xAC000;
const NS = 4096;		// symbol table, one array per field
const R_SYM = 0xAC100;
const sname = 0xAC100, skind = 0xAD100, sval = 0xAE100, ssig = 0xAF100;
const sflag = 0xB0100, sfix = 0xB1100, snext = 0xB2100;
const NL = 512;			// locals, one array per field
const lname = 0xB3100, lslot = 0xB3300, lhome = 0xB3500, lstate = 0xB3700;
const lowner = 0xB3900, lused = 0xB3B00, larr = 0xB3D00, lown = 0xB3F00;	// lown: has owned an object
const NF = 8192;		// patch nodes: a site and a link
const fsite = 0xB4100, fnext = 0xB6100;
const R_SNAP = 0xB8100;		// analyzer snapshots
const R_QBUF = 0xBA100;		// token buffer for quote and grab
const R_SRC = 0xBC100;		// input source stack, 12 words per frame
const R_SEQ = 0xBC500;		// operator code sequences
const bname = 0xBCD00, bprec = 0xBCD40, bseq = 0xBCD80, blen = 0xBCDC0;	// binary operators
const uname = 0xBCE00, useq = 0xBCE20, ulen = 0xBCE40;		// unary operators
const aname = 0xBCE60, abin = 0xBCEA0;				// compound assignment
const kops = 0xBCF00;		// every operator spelling the lexer knows
const R_CTX = 0xBD100;		// saved compiler contexts for nested compiles
const R_LOOP = 0xBD900;		// loop stack, 6 words per loop
const R_ASM = 0xBDD00;		// asm block labels

// ---- token kinds, symbol kinds and flags ----
const T_EOF = 0, T_NUM = 1, T_ID = 2, T_STR = 3, T_OP = 4;
const K_FN = 1, K_GVAR = 2, K_GARR = 3, K_CONST = 4, K_KW = 5;
const F_DEF = 1, F_SIG = 2, F_UNTYPED = 4, F_STMT = 8, F_EXPR = 16, F_TOP = 32;
// variable states for the lifetime analyzer
const S_PLAIN = 0, S_M = 1, S_U = 2, S_D = 3, S_DEAD = 4, S_CHILD = 5, S_BORROW = 6;
// expression classes: plain word, a new object, or a bare variable (C_VAR + index)
const C_PLAIN = 0, C_FRESH = 1, C_VAR = 2;
// lvalue kinds
const LV_NONE = 0, LV_LOCAL = 1, LV_GLOBAL = 2, LV_ELEM = 3, LV_OTHER = 4;
// opcodes
const O_Q = 0, O_LD = 1, O_ST = 2, O_PICK = 3, O_DROP = 4, O_SWAP = 5, O_CALL = 6, O_JMP = 7;
const O_JZ = 8, O_RET = 9, O_ADD = 13, O_SUB = 14;
const SEQREF = -2;		// in an operator sequence: the next word names a symbol

// ---- state ----
var pooltop, nsym, ubase, vislo, nfixu, fixfree;
var nbin, nun, nasg, nkop, seqtop;
var mnem = "q@!$_~cjzr,?.+-*&|^><";
var check_on = 1;		// set to 0 to switch the analyzer off for what follows
var tk, tv, tglue, tline, line = 1, ch, chkind, chptr, qdone, isp = -1;
var tbuf[1100];
var here, hdelta, hlimit, ptop;
var nloc, lbase, fdepth, fslots, fchk, fret, live, bxdepth, epichain, fframe, infn;
var lsp, loopbase, ctxsp, snaptop;
var lv, lvk, lvi, kw_expr, xcls;
// interned spellings the parser compares against
var s_lp, s_rp, s_lb, s_rb, s_lk, s_rk, s_comma, s_semi, s_eq, s_arrow, s_inc, s_dec;
var s_star, s_amp, s_colon, s_hash, s_minus, s_andand, s_oror;
var s_fn, s_var, s_const, s_else, s_as, s_unchecked, s_immediate, s_m, s_d, s_u;
var s_start, s_main, s_free, s_own, s_qnew;

// ---- errors ----
fn die(msg) { puts("zc: line "); putn(tline); puts(": "); puts(msg); putc(10); halt(); return 0; }
fn dien(name, msg) { puts("zc: line "); putn(tline); puts(": "); puts(name); puts(": "); puts(msg); putc(10); halt(); return 0; }
// analyzer errors only count in checked, reachable code
fn cerr(msg) { if (fchk && live) die(msg); return 0; }
fn cerrn(i, msg) { if (fchk && live) dien(lname[i], msg); return 0; }

// ---- interning ----
fn hashs(s) { var h = 0; while (*s) { h = h * 31 + *s; s++; } return h & (IHN - 1); }
fn intern(s)
{
	var h = hashs(s), p, n;
	while (1) {
		p = R_IH[h];
		if (!p) break;
		if (streq(p, s)) return p;
		h = (h + 1) & (IHN - 1);
	}
	n = strlen(s);
	if (pooltop + n + 2 >= R_POOLEND) die("string pool full");
	pooltop[0] = 0;
	p = pooltop + 1;
	wcopy(p, s, n + 1);
	pooltop = pooltop + n + 2;
	R_IH[h] = p;
	return p;
}

// ---- symbols ----
// each interned name keeps the index (+1) of its newest symbol in p[-1], and
// each symbol links to the one it shadows, so lookup is one step.
fn addsym(name, kind, val)
{
	var i = nsym;
	if (nsym >= NS) die("symbol table full");
	nsym++;
	sname[i] = name; skind[i] = kind; sval[i] = val; ssig[i] = 0; sflag[i] = F_DEF; sfix[i] = 0;
	snext[i] = name[-1];
	name[-1] = i + 1;
	return i;
}
// while an image builds, names below vislo are hidden, except keywords
fn lookup(name)
{
	var i = name[-1] - 1;
	while (i >= 0) {
		if (i >= vislo || skind[i] == K_KW) return i;
		i = snext[i] - 1;
	}
	return -1;
}
fn popsyms(to) { while (nsym > to) { nsym--; sname[nsym][-1] = snext[nsym]; } return 0; }
fn lookups(s) { return lookup(intern(s)); }

// patch nodes
fn fixnew(site, link)
{
	var i = fixfree;
	if (i) fixfree = fnext[i];
	else { nfixu++; i = nfixu; if (i >= NF) die("too many forward references"); }
	fsite[i] = site; fnext[i] = link;
	return i;
}
// patch every lit in a chain to point at v, and recycle the nodes
fn fixall(head, v)
{
	var n;
	while (head) { setlit(fsite[head], v); n = fnext[head]; fnext[head] = fixfree; fixfree = head; head = n; }
	return 0;
}

// ---- code emission ----
fn emit(w) { if (here >= hlimit) die("program too big"); *(here + hdelta) = w; here++; return 0; }
fn lit(v) { emit(v + v + 1); return 0; }
fn op(k) { emit(k + k); return 0; }
fn setlit(at, v) { *(at + hdelta) = v + v + 1; return 0; }
fn jmp(t) { lit(t); op(O_JMP); return 0; }
// a lit that will be patched later; returns its address
fn hole() { var a = here; lit(MW - 1); return a; }
fn fwdfn(name) { var s = addsym(name, K_FN, 0); sflag[s] = 0; return s; }
fn fnref(s)
{
	if (sflag[s] & F_DEF) { lit(sval[s]); return 0; }
	sfix[s] = fixnew(here, sfix[s]);
	lit(MW - 1);		// a jump to MW-1 halts if it ever runs unpatched
	return 0;
}
fn callname(name) { var s = lookup(name); if (s < 0) s = fwdfn(name); fnref(s); op(O_CALL); return 0; }
fn laddr(k) { lit(ZFP); op(O_LD); if (k) { lit(k); op(O_ADD); } return 0; }
fn strlit(s)
{
	var j = hole(), a;
	op(O_JMP);
	a = here;
	while (*s) { emit(*s); s++; }
	emit(0);
	setlit(j, here);
	lit(a);
	return 0;
}

// ---- input sources ----
// frame: 0 kind (0 stdin, 1 token list, 2 string)  1 object  2 index  3 end
// 4 transparent  5..7 saved token  8..10 saved char state  11 owned
fn nextch()
{
	if (chkind == 0) {
		if (qdone || eof()) { ch = -1; return 0; }
		ch = getc();
		if (ch == 96) { qdone = 1; ch = -1; return 0; }	// a backtick ends the source
	} else {
		ch = *chptr;
		if (ch) chptr++; else ch = -1;
	}
	if (ch == 10) line++;
	return 0;
}
fn src_push(kind, obj, trans, owned)
{
	var f;
	isp++;
	if (isp >= 32) die("sources nested too deeply");
	f = R_SRC + isp * 12;
	f[0] = kind; f[1] = obj; f[2] = 0; f[3] = 0; f[4] = trans; f[11] = owned;
	f[5] = tk; f[6] = tv; f[7] = tglue; f[8] = ch; f[9] = chkind; f[10] = chptr;
	if (kind == 1) f[3] = obj[0];
	if (kind == 0) { chkind = 0; qdone = 0; nextch(); }
	if (kind == 2) { chkind = 2; chptr = obj; nextch(); }
	return 0;
}
fn src_pop()
{
	var f = R_SRC + isp * 12;
	tk = f[5]; tv = f[6]; tglue = f[7]; ch = f[8]; chkind = f[9]; chptr = f[10];
	isp--;
	if (f[11]) free(f[1]);
	return 0;
}
fn isopch(c)
{
	var s = "+-*/%=<>!&|^~?:.@#$";
	while (*s) { if (*s == c) return 1; s++; }
	return 0;
}
// is buf[0..n) followed by c the start of some operator the lexer knows?
fn opprefix(n, c)
{
	var i = 0, k, j;
	while (i < nkop) {
		k = kops[i];
		j = 0;
		while (j < n && k[j] == tbuf[j]) j++;
		if (j == n && k[n] == c) return 1;
		i++;
	}
	return 0;
}
fn isdig(c) { return c >= '0' && c <= '9'; }
fn isal(c) { return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_'; }
fn hexv(c)
{
	if (isdig(c)) return c - '0';
	if (c >= 'a' && c <= 'f') return c - 'a' + 10;
	if (c >= 'A' && c <= 'F') return c - 'A' + 10;
	return -1;
}
fn escch()
{
	var c = ch;
	nextch();
	if (c != 92) return c;
	c = ch;
	nextch();
	if (c == 'n') return 10;
	if (c == 't') return 9;
	if (c == 'r') return 13;
	if (c == '0') return 0;
	if (c == 'e') return 27;
	return c;
}
fn oplex(n)
{
	while (ch >= 0 && isopch(ch) && opprefix(n, ch)) { tbuf[n] = ch; n++; nextch(); }
	tbuf[n] = 0;
	tk = T_OP; tv = intern(tbuf);
	return 0;
}
fn lex()
{
	var n = 0, v, d;
	tglue = 1;
	while (1) {
		while (ch == 32 || ch == 9 || ch == 10 || ch == 13) { nextch(); tglue = 0; }
		if (ch != '/') break;
		nextch();
		if (ch == '/') { while (ch >= 0 && ch != 10) nextch(); tglue = 0; continue; }
		if (ch == '*') {
			nextch();
			while (ch >= 0) { if (ch == '*') { nextch(); if (ch == '/') break; } else nextch(); }
			nextch(); tglue = 0; continue;
		}
		tline = line; tbuf[0] = '/'; oplex(1); return 0;
	}
	tline = line;
	if (ch < 0) { tk = T_EOF; tv = 0; return 0; }
	if (isdig(ch)) {
		v = 0;
		if (ch == '0') {
			nextch();
			if (ch == 'x' || ch == 'X') {
				nextch();
				while ((d = hexv(ch)) >= 0) { v = v * 16 + d; nextch(); }
				tk = T_NUM; tv = v; return 0;
			}
		}
		while (isdig(ch)) { v = v * 10 + ch - '0'; nextch(); }
		tk = T_NUM; tv = v; return 0;
	}
	if (isal(ch)) {
		while (isal(ch) || isdig(ch)) { if (n < 1000) { tbuf[n] = ch; n++; } nextch(); }
		tbuf[n] = 0;
		tk = T_ID; tv = intern(tbuf); return 0;
	}
	if (ch == 39) { nextch(); tv = escch(); if (ch != 39) die("bad character literal"); nextch(); tk = T_NUM; return 0; }
	if (ch == 34) {
		nextch();
		while (ch >= 0 && ch != 34) { v = escch(); if (n < 1000) { tbuf[n] = v; n++; } }
		nextch();
		tbuf[n] = 0;
		tk = T_STR; tv = intern(tbuf); return 0;
	}
	tbuf[0] = ch;
	nextch();
	if (isopch(tbuf[0])) return oplex(1);
	tbuf[1] = 0;
	tk = T_OP; tv = intern(tbuf);
	return 0;
}
fn next()
{
	var f, q, i;
	f = R_SRC + isp * 12;
	if (f[0] != 1) { lex(); return 0; }
	i = f[2];
	if (i < f[3]) { q = f[1]; tk = q[1 + i + i]; tv = q[2 + i + i]; tglue = 0; f[2] = i + 1; return 0; }
	if (!f[4]) { tk = T_EOF; tv = 0; return 0; }
	src_pop();		// a fed list ran out: continue with the token that followed it
	return 0;
}
fn is_op(s) { return tk == T_OP && tv == s; }
fn is_id(s) { return tk == T_ID && tv == s; }
fn accept(s) { if ((tk == T_OP || tk == T_ID) && tv == s) { next(); return 1; } return 0; }
fn expect(s) { if (!accept(s)) { puts("zc: line "); putn(tline); puts(": expected "); puts(s); putc(10); halt(); } return 0; }
fn name()
{
	var n = tv;
	if (tk != T_ID) die("expected a name");
	next();
	return n;
}

// ---- operator tables ----
// a sequence is written like asm: one-char mnemonics, numbers, and names
// (resolved when the operator is used, so image builds stay self-contained)
fn seqasm(s)
{
	var start = seqtop, n, neg, v, k, c;
	while (1) {
		while (*s == 32) s++;
		if (!*s) break;
		n = 0;
		while (s[n] && s[n] != 32) { tbuf[n] = s[n]; n++; }
		tbuf[n] = 0;
		s = s + n;
		neg = tbuf[0] == '-' && isdig(tbuf[1]);
		if (isdig(tbuf[neg])) {
			v = 0; k = neg;
			while (tbuf[k]) { v = v * 10 + tbuf[k] - '0'; k++; }
			if (neg) v = 0 - v;
			R_SEQ[seqtop] = v + v + 1; seqtop++;
		} else if (n == 1 && (c = mnemidx(tbuf[0])) >= 0) {
			R_SEQ[seqtop] = c + c; seqtop++;
		} else {
			R_SEQ[seqtop] = SEQREF; R_SEQ[seqtop + 1] = intern(tbuf); seqtop = seqtop + 2;
		}
	}
	return start;
}
fn mnemidx(c) { var i = 0; while (mnem[i]) { if (mnem[i] == c) return i; i++; } return -1; }
fn emitseq(a, n)
{
	var e = a + n, s;
	while (a < e) {
		if (R_SEQ[a] == SEQREF) {
			s = lookup(R_SEQ[a + 1]);
			if (s < 0) s = fwdfn(R_SEQ[a + 1]);
			if (skind[s] == K_FN) fnref(s); else lit(sval[s]);
			a = a + 2;
		} else { emit(R_SEQ[a]); a++; }
	}
	return 0;
}
fn addkop(p) { var i = 0; while (i < nkop) { if (kops[i] == p) return 0; i++; } kops[nkop] = p; nkop++; return 0; }
fn binfind(p) { var i = nbin; while (i) { i--; if (bname[i] == p) return i; } return -1; }
fn unfind(p) { var i = nun; while (i) { i--; if (uname[i] == p) return i; } return -1; }
fn asgfind(p) { var i = nasg; while (i) { i--; if (aname[i] == p) return i; } return -1; }
// add or replace a binary operator. code is a sequence string, or 0 for the
// built-in && (prec 2) and || (prec 1) behaviour, chosen by -1 / -2 in prec.
fn add_binop(nm, prec, code)
{
	var p = intern(nm), i = binfind(p), a, n;
	if (i < 0) { i = nbin; nbin++; }
	bname[i] = p; bprec[i] = prec;
	if (prec < 0) { bprec[i] = 0 - prec; blen[i] = prec; bseq[i] = 0; addkop(p); return i; }
	bseq[i] = seqasm(code); blen[i] = seqtop - bseq[i];
	addkop(p);
	// and its compound assignment, x op= y
	n = strlen(nm);
	wcopy(tbuf + 1000, nm, n);
	tbuf[1000 + n] = '='; tbuf[1001 + n] = 0;
	a = intern(tbuf + 1000);
	if (prec >= 8 || prec == 5 || prec == 4 || prec == 3) {
		if (asgfind(a) < 0) { aname[nasg] = a; nasg++; }
		abin[asgfind(a)] = i;
		addkop(a);
	}
	return i;
}
fn add_unop(nm, code)
{
	var p = intern(nm), i = unfind(p);
	if (i < 0) { i = nun; nun++; }
	uname[i] = p; useq[i] = seqasm(code); ulen[i] = seqtop - useq[i];
	addkop(p);
	return i;
}
fn add_kw(nm, handler, flags) { var s = addsym(intern(nm), K_KW, handler); sflag[s] = F_DEF | flags; return s; }

// ---- locals and the analyzer's view of them ----
fn findloc(n) { var i = nloc; while (i > lbase) { i--; if (lname[i] == n) return i; } return -1; }
fn newloc(n)
{
	var i = nloc;
	if (nloc >= NL) die("too many locals");
	nloc++;
	lname[i] = n; lslot[i] = fslots; lhome[i] = fdepth; lstate[i] = S_PLAIN;
	lowner[i] = 0; lused[i] = 0; larr[i] = 0; lown[i] = 0;
	return i;
}
fn lroot(i) { while (lstate[i] == S_CHILD) i = lowner[i]; return i; }
fn tracked(i) { return lstate[i] != S_PLAIN; }
// a use that doesn't give the object away
fn touch(i)
{
	var r;
	lused[i] = 1;
	if (!fchk) return 0;
	r = lroot(i);
	lused[r] = 1;
	if (lstate[r] == S_DEAD) { cerrn(i, "used after it was given away"); return 0; }
	// a d object that shows up in a deeper block is given to that block
	if (lstate[r] == S_D && lhome[r] < fdepth) { lhome[r] = fdepth; lstate[r] = S_M; lown[r] = 1; }
	return 0;
}
fn plainuse(c)
{
	if (c == C_FRESH) cerr("a new object can't be used as a plain value; bind it to a name first");
	if (c >= C_VAR) touch(c - C_VAR);
	return C_PLAIN;
}
fn freevar(i) { laddr(lslot[i]); op(O_LD); callname(s_free); op(O_DROP); return 0; }
// leaving every block deeper than or equal to dep: free what is owned, and
// complain about what should have left already. final means the block really
// ends here rather than an early exit.
fn exit_vars(dep, final)
{
	var i = nloc, st;
	if (!fchk || !live) return 0;
	while (i > lbase) {
		i--;
		if (lhome[i] < dep) continue;
		st = lstate[i];
		if (st == S_M) freevar(i); else if (st == S_U) cerrn(i, "u object must leave this block (block value, assignment to the enclosing block, or return)");
		else if (st == S_D) cerrn(i, "d object was never given away");
	}
	return 0;
}
// an m object has to be used somewhere in the block that owns it, on any path
fn unused_check(from)
{
	while (from < nloc) { if (fchk && lown[from] && !lused[from]) dien(lname[from], "m object is never used"); from++; }
	return 0;
}
fn block_close(save)
{
	var i = lbase;
	unused_check(save);
	exit_vars(fdepth, 1);
	while (i < save) { if (lhome[i] >= fdepth) { lstate[i] = S_DEAD; lhome[i] = fdepth - 1; } i++; }
	nloc = save;
	return 0;
}

// snapshots: [lbase] [nloc] then state, owner, home per local
fn snap_push()
{
	var b = snaptop, i = lbase, p;
	p = R_SNAP + b;
	p[0] = lbase; p[1] = nloc;
	p = p + 2;
	while (i < nloc) { p[0] = lstate[i]; p[1] = lowner[i]; p[2] = lhome[i]; p = p + 3; i++; }
	snaptop = p - R_SNAP;
	if (snaptop >= 8000) die("nesting too deep for the analyzer");
	return b;
}
fn snap_pop(b) { snaptop = b; return 0; }
fn snap_restore(b)
{
	var p = R_SNAP + b, i = p[0], e = p[1];
	if (e > nloc) e = nloc;
	p = p + 2;
	while (i < e) { lstate[i] = p[0]; lowner[i] = p[1]; lhome[i] = p[2]; p = p + 3; i++; }
	return 0;
}
fn empty(s) { return s == S_PLAIN || s == S_DEAD; }
// compare the current states with a snapshot: -1 if they agree, else the
// first local that differs. plain and dead agree and merge to dead.
fn snap_cmp(b)
{
	var p = R_SNAP + b, i = p[0], e = p[1], s;
	if (e > nloc) e = nloc;
	p = p + 2;
	while (i < e) {
		s = lstate[i];
		if (empty(s) && empty(p[0])) { if (p[0] == S_DEAD) lstate[i] = S_DEAD; }
		else if (s != p[0] || lhome[i] != p[2] || (s == S_CHILD && lowner[i] != p[1])) return i;
		p = p + 3; i++;
	}
	return -1;
}
fn statename(s)
{
	if (s == S_PLAIN) return "empty";
	if (s == S_M) return "m";
	if (s == S_U) return "u";
	if (s == S_D) return "d";
	if (s == S_DEAD) return "given away";
	if (s == S_CHILD) return "owned by a container";
	return "borrowed";
}
fn merge_err(i, sa, what)
{
	if (!fchk) return 0;
	puts("zc: line "); putn(tline); puts(": "); puts(lname[i]); puts(": "); puts(what);
	puts(" (one path leaves it "); puts(statename(sa)); puts(", another "); puts(statename(lstate[i])); puts(")\n");
	halt();
	return 0;
}
// after an if: the current state is the else path, sa is the then path
fn merge(sa, livea)
{
	var i, p;
	if (!livea) return 0;
	if (!live) { snap_restore(sa); live = 1; return 0; }
	i = snap_cmp(sa);
	if (i >= 0) { p = R_SNAP + sa + 2 + 3 * (i - R_SNAP[sa]); merge_err(i, p[0], "ends the branches of an if in different states"); }
	return 0;
}
fn loopcheck(s0)
{
	var i, p;
	if (!fchk || !live) return 0;
	i = snap_cmp(s0);
	if (i >= 0) { p = R_SNAP + s0 + 2 + 3 * (i - R_SNAP[s0]); merge_err(i, p[0], "changes state inside a loop; each pass has to leave it as it found it"); }
	return 0;
}

// ---- analyzer rules for the places values flow ----
// recast: x as u / x as d / x as m
fn recast(c, t)
{
	var i, st;
	if (!fchk) return c;
	if (c < C_VAR) { cerr("only a named owned object can be recast"); return c; }
	i = c - C_VAR;
	st = lstate[i];
	lused[i] = 1;
	if (st == S_CHILD) cerrn(i, "belongs to a container; recast the container instead");
	else if (st == S_BORROW) cerrn(i, "is borrowed and can't be recast");
	else if (st == S_PLAIN) cerrn(i, "isn't an owned object");
	else if (st == S_DEAD) cerrn(i, "used after it was given away");
	else if (t == S_M && st != S_M) cerrn(i, "can't be recast back to m");
	else lstate[i] = t;
	return c;
}
// an argument for a parameter tagged t (0 plain, 1 m, 2 d)
fn argcheck(c, t)
{
	var i, st;
	if (!fchk) return 0;
	if (c == C_FRESH) { if (t != 2) cerr("a new object can only go straight to a d parameter; bind it to a name first"); return 0; }
	if (c < C_VAR || !tracked(c - C_VAR)) return 0;
	i = c - C_VAR;
	st = lstate[i];
	if (lstate[lroot(i)] == S_DEAD) { cerrn(i, "used after it was given away"); return 0; }
	if (t == 0) { cerrn(i, "is an owned object; it can only be passed to an m or d parameter"); return 0; }
	if (t == 1) {
		if (st == S_D) { cerrn(i, "is d; pass it to a d parameter (lending it would lose it)"); return 0; }
		touch(i);
		return 0;
	}
	if (st == S_D) { lstate[i] = S_DEAD; lused[i] = 1; return 0; }
	if (st == S_M) cerrn(i, "is m; write 'as d' to give it away");
	else if (st == S_U) cerrn(i, "is u; write 'as d' to give it away instead of returning it");
	else if (st == S_CHILD) cerrn(i, "belongs to a container and can't be given away alone");
	else cerrn(i, "is borrowed and can't be given away");
	return 0;
}
fn emitown(p) { laddr(lslot[p]); op(O_LD); callname(s_own); return 0; }
// a store of class rc into an lvalue of kind k (local or container index i)
fn assigncheck(k, i, rc)
{
	var st, j, r, js;
	if (!fchk) return C_PLAIN;
	j = -1;
	if (rc >= C_VAR && tracked(rc - C_VAR)) j = rc - C_VAR;
	if (j >= 0 && lstate[lroot(j)] == S_DEAD) { cerrn(j, "used after it was given away"); return C_PLAIN; }
	if (k == LV_LOCAL) {
		st = lstate[i];
		if (j < 0 && rc != C_FRESH) {
			if (!empty(st)) cerrn(i, "still owns an object; overwriting it would leak it");
			else lstate[i] = S_PLAIN;
			return C_PLAIN;
		}
		if (!empty(st)) { cerrn(i, "still owns an object; overwriting it would leak it"); return C_PLAIN; }
		if (rc == C_FRESH) { lstate[i] = S_M; lused[i] = 0; lown[i] = 1; return C_PLAIN; }
		js = lstate[j];
		if (js == S_U && lhome[i] == lhome[j] - 1) {	// handing a u object up one block
			lstate[i] = S_M; lused[i] = 0; lown[i] = 1; lstate[j] = S_DEAD; lused[j] = 1;
			return C_PLAIN;
		}
		if (js == S_U) cerrn(j, "is u; it can only be handed to a variable of the enclosing block, or returned");
		else cerrn(j, "is an owned object and can't be copied into another variable");
		return C_PLAIN;
	}
	if (k == LV_ELEM) {
		r = lroot(i);
		st = lstate[r];
		touch(i);
		if (rc == C_FRESH) { emitown(i); return C_PLAIN; }
		if (j < 0) return C_PLAIN;
		js = lstate[j];
		if (js == S_CHILD) cerrn(j, "already belongs to a container");
		else if (js == S_BORROW) cerrn(j, "is borrowed and can't be stored");
		else if (st == S_BORROW) {
			if (js != S_D) cerrn(j, "must be d to be stored into a borrowed object");
			else { lstate[j] = S_DEAD; lused[j] = 1; emitown(i); }
		} else if (js != st) cerrn(j, "its tag doesn't match its container's (both have to be m, u or d)");
		else if (lhome[j] < lhome[r]) cerrn(j, "lives in an outer block than the container it's stored into");
		else { lstate[j] = S_CHILD; lowner[j] = i; lused[j] = 1; emitown(i); }
		return C_PLAIN;
	}
	// a global, or memory the analyzer doesn't track: the collector takes it
	if (j >= 0) {
		if (lstate[j] == S_D) { lstate[j] = S_DEAD; lused[j] = 1; }
		else cerrn(j, "must be d to be stored in a global or in untracked memory (the collector takes it over)");
	}
	return C_PLAIN;
}
fn retcheck(c)
{
	var i;
	if (!fchk) return 0;
	i = -1;
	if (c >= C_VAR && tracked(c - C_VAR)) i = c - C_VAR;
	if (i >= 0 && lstate[lroot(i)] == S_DEAD) { cerrn(i, "used after it was given away"); return 0; }
	if (fret) {
		if (i >= 0) {
			if (lstate[i] == S_U) { lstate[i] = S_DEAD; lused[i] = 1; }
			else cerrn(i, "has to be u to be returned; write 'return x as u'");
		}
		return 0;
	}
	if (c == C_FRESH) cerr("returns a new object; declare the function with -> u");
	else if (i >= 0) cerrn(i, "is owned and can't be returned from a function without -> u");
	return 0;
}
// the last expression of a block expression
fn handup(c)
{
	var i;
	if (!fchk) return C_PLAIN;
	if (c == C_FRESH) return C_FRESH;
	if (c < C_VAR || !tracked(c - C_VAR)) return C_PLAIN;
	i = c - C_VAR;
	if (lstate[i] == S_U && lhome[i] == fdepth) { lstate[i] = S_DEAD; lused[i] = 1; return C_FRESH; }
	if (lstate[i] == S_U) cerrn(i, "only a u object of this block can be its value");
	else cerrn(i, "has to be u to be handed up as the block's value");
	return C_PLAIN;
}
fn discard(c)
{
	if (c == C_FRESH) cerr("a new object (or a u result) can't be thrown away");
	else if (c >= C_VAR) touch(c - C_VAR);
	return 0;
}

// ---- expressions ----
fn rval() { if (lv) { op(O_LD); lv = 0; } return 0; }
fn kwcall(s, e)
{
	var f = sval[s], old = kw_expr, c;
	kw_expr = e; xcls = C_PLAIN;
	f();
	kw_expr = old;
	c = xcls;
	lv = 0; lvk = LV_NONE;
	return c;
}
fn stmtonly() { if (kw_expr) die("this can't be used inside an expression"); return 0; }
fn call(s)
{
	var np = 0, tags = 0, ret = 0, c;
	if (sflag[s] & F_SIG) { tags = ssig[s] >> 6; ret = ssig[s] & 1; }
	else sflag[s] = sflag[s] | F_UNTYPED;
	expect(s_lp);
	if (!is_op(s_rp)) {
		while (1) {
			c = expr(); rval();
			argcheck(c, (tags >> (np + np)) & 3);
			np++;
			if (!accept(s_comma)) break;
		}
	}
	expect(s_rp);
	if ((sflag[s] & F_SIG) && np != ((ssig[s] >> 1) & 31)) dien(sname[s], "wrong number of arguments");
	fnref(s); op(O_CALL);
	lv = 0; lvk = LV_NONE;
	if (ret) return C_FRESH;
	return C_PLAIN;
}
fn primary()
{
	var n, i, s, c;
	lv = 0; lvk = LV_NONE;
	if (tk == T_NUM) { lit(tv); next(); return C_PLAIN; }
	if (tk == T_STR) { strlit(tv); next(); return C_PLAIN; }
	if (tk == T_OP) {
		if (tv == s_lp) { next(); c = expr(); expect(s_rp); return c; }
		if (tv == s_lb) return blockexpr();
		die("expected an expression");
	}
	if (tk != T_ID) die("expected an expression");
	n = tv;
	i = findloc(n);
	if (i >= 0) {
		next();
		if (!fchk && tracked(i)) dien(n, "is tracked by the analyzer and can't be used in unchecked code");
		laddr(lslot[i]);
		if (larr[i]) return C_PLAIN;
		lv = 1; lvk = LV_LOCAL; lvi = i;
		if (tracked(i)) return C_VAR + i;
		return C_PLAIN;
	}
	s = lookup(n);
	if (s >= 0 && skind[s] == K_KW) {
		if (!(sflag[s] & F_EXPR)) dien(n, "can't be used inside an expression");
		return kwcall(s, 1);
	}
	next();
	if (s >= 0 && skind[s] == K_CONST) { lit(sval[s]); return C_PLAIN; }
	if (s >= 0 && skind[s] == K_GVAR) { lit(sval[s]); lv = 1; lvk = LV_GLOBAL; return C_PLAIN; }
	if (s >= 0 && skind[s] == K_GARR) { lit(sval[s]); return C_PLAIN; }
	if (s < 0) s = fwdfn(n);
	if (is_op(s_lp)) return call(s);
	fnref(s);
	return C_PLAIN;
}
// ++ and -- on the address at the top of the stack
fn incdec(post, d)
{
	if (!lv) die("++ and -- need something to assign to");
	if (lvk == LV_LOCAL && fchk && tracked(lvi)) cerrn(lvi, "owns an object and can't be incremented");
	lv = 0; lvk = LV_NONE;
	lit(0); op(O_PICK); op(O_LD);
	if (post) { lit(0); op(O_PICK); lit(d); op(O_ADD); lit(2); op(O_PICK); op(O_ST); }
	else { lit(d); op(O_ADD); lit(0); op(O_PICK); lit(2); op(O_PICK); op(O_ST); }
	op(O_SWAP); op(O_DROP);
	return C_PLAIN;
}
fn postfix()
{
	var c = primary(), b, n, t;
	while (1) {
		if (tk == T_ID && tv == s_as) {
			next();
			if (tk != T_ID) die("expected u, d or m after as");
			t = S_M;
			if (tv == s_u) t = S_U; else if (tv == s_d) t = S_D; else if (tv != s_m) die("expected u, d or m after as");
			next();
			rval();
			c = recast(c, t);
			lvk = LV_NONE;
			continue;
		}
		if (tk != T_OP) return c;
		if (tv == s_lk) {
			next();
			rval();
			b = -1;
			if (c == C_FRESH) cerr("index a new object only after binding it to a name");
			else if (c >= C_VAR) { touch(c - C_VAR); b = c - C_VAR; }
			c = expr(); rval(); plainuse(c);
			expect(s_rk);
			op(O_ADD);
			lv = 1;
			if (b >= 0) { lvk = LV_ELEM; lvi = b; } else lvk = LV_OTHER;
			c = C_PLAIN;
			continue;
		}
		if (tv == s_lp) {	// call through a value
			rval(); plainuse(c);
			next();
			n = 0;
			if (!is_op(s_rp)) { while (1) { c = expr(); rval(); argcheck(c, 0); n++; if (!accept(s_comma)) break; } }
			expect(s_rp);
			lit(n); op(O_PICK); op(O_CALL); op(O_SWAP); op(O_DROP);
			lv = 0; lvk = LV_NONE; c = C_PLAIN;
			continue;
		}
		if (tv == s_inc) { next(); c = incdec(1, 1); continue; }
		if (tv == s_dec) { next(); c = incdec(1, -1); continue; }
		return c;
	}
	return c;
}
fn unary()
{
	var c, u;
	if (tk == T_OP) {
		if (tv == s_star) { next(); c = unary(); rval(); plainuse(c); lv = 1; lvk = LV_OTHER; return C_PLAIN; }
		if (tv == s_amp) {
			next(); c = unary();
			if (!lv) die("& needs something addressable");
			if (c >= C_VAR) touch(c - C_VAR);
			lv = 0; lvk = LV_NONE;
			return C_PLAIN;
		}
		if (tv == s_inc) { next(); unary(); return incdec(0, 1); }
		if (tv == s_dec) { next(); unary(); return incdec(0, -1); }
		u = unfind(tv);
		if (u >= 0) {
			next(); c = unary(); rval(); plainuse(c);
			emitseq(useq[u], ulen[u]);
			lv = 0; lvk = LV_NONE;
			return C_PLAIN;
		}
	}
	return postfix();
}
fn bin(minp)
{
	var c = unary(), b, p, a, j;
	while (tk == T_OP) {
		b = binfind(tv);
		if (b < 0) return c;
		p = bprec[b];
		if (p < minp) return c;
		next(); rval(); plainuse(c);
		if (blen[b] == -1) {		// && : 0 if the left side is 0, else the right side as 0 or 1
			a = hole(); op(O_JZ);
			c = bin(p + 1); rval(); plainuse(c);
			emitseq(useq[1], ulen[1]);	// !! normalizes
			j = hole(); op(O_JMP);
			setlit(a, here); lit(0); setlit(j, here);
		} else if (blen[b] == -2) {	// || : 1 if the left side isn't 0, else the right side as 0 or 1
			a = hole(); op(O_JZ);
			lit(1); j = hole(); op(O_JMP);
			setlit(a, here);
			c = bin(p + 1); rval(); plainuse(c);
			emitseq(useq[1], ulen[1]);
			setlit(j, here);
		} else {
			c = bin(p + 1); rval(); plainuse(c);
			emitseq(bseq[b], blen[b]);
		}
		lv = 0; lvk = LV_NONE; c = C_PLAIN;
	}
	return c;
}
// [addr v] -> [v], storing v at addr
fn storekeep() { op(O_SWAP); lit(1); op(O_PICK); op(O_SWAP); op(O_ST); return 0; }
fn expr()
{
	var c = bin(1), k, i, a, rc;
	if (tk != T_OP) return c;
	if (tv == s_eq) {
		if (!lv) die("this can't be assigned to");
		k = lvk; i = lvi;
		next();
		rc = expr(); rval();
		storekeep();
		lv = 0; lvk = LV_NONE;
		return assigncheck(k, i, rc);
	}
	a = asgfind(tv);
	if (a >= 0) {
		if (!lv) die("this can't be assigned to");
		if (lvk == LV_LOCAL && fchk && tracked(lvi)) cerrn(lvi, "owns an object; compound assignment would lose it");
		next();
		lit(0); op(O_PICK); op(O_LD);
		lv = 0;
		rc = expr(); rval(); plainuse(rc);
		emitseq(bseq[abin[a]], blen[abin[a]]);
		storekeep();
		lv = 0; lvk = LV_NONE;
		return C_PLAIN;
	}
	return c;
}
// does the current token start a statement rather than an expression?
fn stmtstart()
{
	var s;
	if (tk == T_OP) return tv == s_semi || tv == s_lb;
	if (tk != T_ID || findloc(tv) >= 0) return 0;
	s = lookup(tv);
	return s >= 0 && skind[s] == K_KW && !(sflag[s] & F_EXPR);
}
// { stmts; tail } as an expression: its value is the tail, or 0
fn blockexpr()
{
	var save = nloc, c = C_PLAIN, tail = 0;
	next();
	fdepth++; bxdepth++;
	while (!is_op(s_rb)) {
		if (tk == T_EOF) die("missing }");
		if (stmtstart()) { stmt(); continue; }
		c = expr(); rval();
		if (accept(s_semi)) { op(O_DROP); discard(c); c = C_PLAIN; continue; }
		if (!is_op(s_rb)) die("expected ; or } after an expression");
		tail = 1;
	}
	next();
	if (tail) c = handup(c); else lit(0);
	block_close(save);
	fdepth--; bxdepth--;
	lv = 0; lvk = LV_NONE;
	return c;
}

// ---- constant expressions ----
fn cprim()
{
	var v, s;
	if (tk == T_NUM) { v = tv; next(); return v; }
	if (accept(s_minus)) return 0 - cprim();
	if (tk == T_OP && tv == uname[2]) { next(); return ~cprim(); }
	if (accept(s_lp)) { v = cexpr(); expect(s_rp); return v; }
	if (tk == T_ID) {
		s = lookup(tv);
		if (s >= 0 && (skind[s] == K_CONST || skind[s] == K_GARR || (skind[s] == K_FN && (sflag[s] & F_DEF)) || skind[s] == K_GVAR)) { next(); return sval[s]; }
	}
	die("expected a constant");
	return 0;
}
fn cexpr()
{
	var v = cprim(), o;
	while (tk == T_OP) {
		o = tv;
		if (o == bname[3]) { next(); v = v + cprim(); }
		else if (o == bname[4]) { next(); v = v - cprim(); }
		else if (o == bname[0]) { next(); v = v * cprim(); }
		else if (o == bname[15]) { next(); v = v | cprim(); }
		else if (o == bname[13]) { next(); v = v & cprim(); }
		else if (o == bname[5]) { next(); v = v << cprim(); }
		else if (o == bname[6]) { next(); v = v >> cprim(); }
		else return v;
	}
	return v;
}

// ---- statements ----
fn stmt()
{
	var s, c;
	if (tk == T_ID && findloc(tv) < 0) {
		s = lookup(tv);
		if (s >= 0 && skind[s] == K_KW && (sflag[s] & F_STMT)) { kwcall(s, 0); return 0; }
	}
	if (tk == T_OP) {
		if (tv == s_semi) { next(); return 0; }
		if (tv == s_lb) { block(); return 0; }
	}
	c = expr(); rval(); op(O_DROP);
	expect(s_semi);
	discard(c);
	return 0;
}
fn block()
{
	var save = nloc;
	expect(s_lb);
	fdepth++;
	while (!is_op(s_rb)) { if (tk == T_EOF) die("missing }"); stmt(); }
	next();
	block_close(save);
	fdepth--;
	return 0;
}
// the body of if/while/for: its own block, even without braces
fn substmt()
{
	var save = nloc;
	if (is_op(s_lb)) return block();
	fdepth++;
	stmt();
	block_close(save);
	fdepth--;
	return 0;
}
fn kw_var()
{
	var n, i, c, k;
	stmtonly();
	next();
	while (1) {
		n = name();
		i = newloc(n);
		if (accept(s_lk)) { k = cexpr(); expect(s_rk); larr[i] = 1; fslots = fslots + k; }
		else fslots++;
		if (accept(s_eq)) { c = expr(); rval(); laddr(lslot[i]); op(O_ST); assigncheck(LV_LOCAL, i, c); }
		if (!accept(s_comma)) break;
	}
	expect(s_semi);
	return 0;
}
fn kw_if()
{
	var a, b, c, s0, sa, live0, livea;
	stmtonly();
	next();
	expect(s_lp); c = expr(); rval(); plainuse(c); expect(s_rp);
	a = hole(); op(O_JZ);
	live0 = live;
	s0 = snap_push();
	substmt();
	livea = live; sa = snap_push();
	if (is_id(s_else)) {
		next();
		b = hole(); op(O_JMP);
		setlit(a, here);
		snap_restore(s0); live = live0;
		substmt();
		setlit(b, here);
	} else { setlit(a, here); snap_restore(s0); live = live0; }
	merge(sa, livea);
	snap_pop(s0);
	return 0;
}
// loop frame: 0 continue target  1 break chain  2 depth  3 snapshot  4 block-expression depth
fn loop_push(cont, s0)
{
	var f = R_LOOP + lsp * 6;
	if (lsp >= 60) die("loops nested too deeply");
	f[0] = cont; f[1] = 0; f[2] = fdepth; f[3] = s0; f[4] = bxdepth;
	lsp++;
	return 0;
}
fn loop_pop() { lsp--; fixall(R_LOOP[lsp * 6 + 1], here); return 0; }
fn kw_while()
{
	var c0 = here, a, s0, c;
	stmtonly();
	next();
	s0 = snap_push();
	expect(s_lp); c = expr(); rval(); plainuse(c); expect(s_rp);
	a = hole(); op(O_JZ);
	loop_push(c0, s0);
	substmt();
	loopcheck(s0);
	jmp(c0);
	setlit(a, here);
	loop_pop();
	snap_restore(s0); live = 1;
	snap_pop(s0);
	return 0;
}
fn kw_for()
{
	var save = nloc, s0, c0, a, b, d, c;
	stmtonly();
	next();
	expect(s_lp);
	fdepth++;
	if (is_id(s_var)) kw_var();
	else { if (!is_op(s_semi)) { c = expr(); rval(); op(O_DROP); discard(c); } expect(s_semi); }
	s0 = snap_push();
	c0 = here;
	if (!is_op(s_semi)) { c = expr(); rval(); plainuse(c); } else lit(1);
	expect(s_semi);
	a = hole(); op(O_JZ);
	b = hole(); op(O_JMP);
	d = here;
	if (!is_op(s_rp)) { c = expr(); rval(); op(O_DROP); discard(c); }
	expect(s_rp);
	jmp(c0);
	setlit(b, here);
	loop_push(d, s0);
	substmt();
	loopcheck(s0);
	jmp(d);
	setlit(a, here);
	loop_pop();
	snap_restore(s0); live = 1;
	snap_pop(s0);
	block_close(save);
	fdepth--;
	return 0;
}
fn loopexit(f)
{
	if (lsp <= loopbase) die("break or continue outside a loop");
	if (f[4] != bxdepth) die("break and continue can't leave a block expression");
	loopcheck(f[3]);
	exit_vars(f[2] + 1, 0);
	return 0;
}
fn kw_break()
{
	var f = R_LOOP + (lsp - 1) * 6;
	stmtonly();
	next(); expect(s_semi);
	loopexit(f);
	f[1] = fixnew(here, f[1]);
	lit(MW - 1); op(O_JMP);
	live = 0;
	return 0;
}
fn kw_continue()
{
	var f = R_LOOP + (lsp - 1) * 6;
	stmtonly();
	next(); expect(s_semi);
	loopexit(f);
	jmp(f[0]);
	live = 0;
	return 0;
}
fn kw_return()
{
	var c;
	stmtonly();
	next();
	if (!infn) die("return outside a function");
	if (bxdepth) die("return can't leave a block expression");
	if (is_op(s_semi)) { lit(0); c = C_PLAIN; } else { c = expr(); rval(); }
	expect(s_semi);
	retcheck(c);
	exit_vars(1, 0);
	epichain = fixnew(here, epichain);
	lit(MW - 1); op(O_JMP);
	live = 0;
	return 0;
}
fn kw_unchecked()
{
	var old = fchk;
	stmtonly();
	next();
	fchk = 0;
	substmt();
	fchk = old;
	return 0;
}

// ---- asm blocks: raw vm words, one per token ----
// numbers push, -n pushes a negative number, #n emits a raw word, one-char
// tokens from the mnemonic table are opcodes, names push the address of a
// variable or function, :name defines a label for this block.
fn asmblock()
{
	var nl = 0, nr = 0, i, k, c, s, ln = R_ASM, la = R_ASM + 64, rn = R_ASM + 128, ra = R_ASM + 384;
	expect(s_lb);
	while (!is_op(s_rb)) {
		if (tk == T_EOF) die("unterminated asm block");
		if (tk == T_NUM) { lit(tv); next(); continue; }
		if (tk == T_STR) { strlit(tv); next(); continue; }
		if (is_op(s_hash)) { next(); if (tk != T_NUM) die("# needs a number"); emit(tv); next(); continue; }
		if (is_op(s_minus)) { next(); if (tk == T_NUM && tglue) { lit(0 - tv); next(); } else op(O_SUB); continue; }
		if (is_op(s_colon)) { next(); if (nl >= 64) die("too many asm labels"); ln[nl] = name(); la[nl] = here; nl++; continue; }
		if (tv[0] && !tv[1] && (c = mnemidx(tv[0])) >= 0) { op(c); next(); continue; }
		if (tk != T_ID) die("bad token in asm");
		i = findloc(tv);
		if (i >= 0) { lused[i] = 1; laddr(lslot[i]); next(); continue; }
		k = -1; i = 0;
		while (i < nl) { if (ln[i] == tv) k = i; i++; }
		if (k >= 0) { lit(la[k]); next(); continue; }
		s = lookup(tv);
		if (s >= 0 && skind[s] != K_FN && skind[s] != K_KW) { lit(sval[s]); next(); continue; }
		if (s >= 0 && skind[s] == K_FN) { fnref(s); next(); continue; }
		if (nr >= 250) die("too many asm label references");
		rn[nr] = tv; ra[nr] = hole(); nr++; next();	// a label further down this block
	}
	next();
	i = 0;
	while (i < nr) {
		k = -1; c = 0;
		while (c < nl) { if (ln[c] == rn[i]) k = c; c++; }
		if (k < 0) dien(rn[i], "unknown name in asm");
		setlit(ra[i], la[k]);
		i++;
	}
	return 0;
}
fn kw_asm() { next(); asmblock(); xcls = C_PLAIN; return 0; }

// ---- quote: code as data ----
// a token list is an object: [n] then kind, value for each token. names,
// strings and operators are interned pointers.
fn grab() -> u
{
	var n = 0, depth = 0, q;
	if (!is_op(s_lb)) die("expected {");
	next();
	while (1) {
		if (tk == T_EOF) die("unterminated quote");
		if (is_op(s_lb)) depth++;
		if (is_op(s_rb)) { if (!depth) break; depth--; }
		if (n >= 4000) die("quote too long");
		R_QBUF[n + n] = tk; R_QBUF[n + n + 1] = tv; n++;
		next();
	}
	next();
	q = new(n + n + 1);
	q[0] = n;
	wcopy(q + 1, R_QBUF, n + n);
	return q as u;
}
unchecked fn qnew(src) -> u { var n = src[0] * 2 + 1, q = new(n); wcopy(q, src, n); return q; }
fn qdup(m q) -> u { var n = q[0] * 2 + 1, r = new(n); wcopy(r, q, n); return r as u; }
fn wcopyto(m q, n) { var i = 0; while (i < n) { emit(q[i]); i++; } return 0; }
fn kw_quote()
{
	var q, j, a, n;
	next();
	q = grab();
	j = hole(); op(O_JMP);
	a = here;
	n = q[0] * 2 + 1;
	wcopyto(q, n);
	free(q as d);
	setlit(j, here);
	lit(a);
	callname(s_qnew);
	xcls = C_FRESH;
	return 0;
}
// tokens of a string, as a token list
fn tokens(s) -> u
{
	var n = 0, q;
	src_push(2, s, 0, 0);
	next();
	while (tk != T_EOF) {
		if (n >= 4000) die("too many tokens");
		R_QBUF[n + n] = tk; R_QBUF[n + n + 1] = tv; n++;
		next();
	}
	src_pop();
	q = new(n + n + 1);
	q[0] = n;
	wcopy(q + 1, R_QBUF, n + n);
	return q as u;
}
// feed a token list into the input: the parser reads it next, then carries
// on where it was. the list is freed once it has been read.
unchecked fn feed(d q) { src_push(1, q, 1, 1); next(); return 0; }

// ---- nested compiles ----
// compile() and load() can run while another function is being compiled (from
// a parse word). the function context is saved, the new code is emitted in
// place with a jump around it, and then everything is put back.
fn ctx_push()
{
	var f = R_CTX + ctxsp * 24;
	if (ctxsp >= 30) die("compiles nested too deeply");
	ctxsp++;
	f[0] = nloc; f[1] = lbase; f[2] = fdepth; f[3] = fslots; f[4] = fchk; f[5] = fret; f[6] = live;
	f[7] = bxdepth; f[8] = epichain; f[9] = fframe; f[10] = infn; f[11] = lsp; f[12] = loopbase;
	f[13] = lv; f[14] = lvk; f[15] = lvi; f[16] = kw_expr; f[17] = xcls; f[18] = snaptop;
	return 0;
}
fn ctx_pop()
{
	var f;
	ctxsp--;
	f = R_CTX + ctxsp * 24;
	nloc = f[0]; lbase = f[1]; fdepth = f[2]; fslots = f[3]; fchk = f[4]; fret = f[5]; live = f[6];
	bxdepth = f[7]; epichain = f[8]; fframe = f[9]; infn = f[10]; lsp = f[11]; loopbase = f[12];
	lv = f[13]; lvk = f[14]; lvi = f[15]; kw_expr = f[16]; xcls = f[17]; snaptop = f[18];
	return 0;
}

// ---- functions and the top level ----
fn fn_begin(chk, ret)
{
	lbase = nloc; fdepth = 1; fslots = 0; fchk = chk && check_on; fret = ret;
	live = 1; bxdepth = 0; epichain = 0; infn = 1; loopbase = lsp; lv = 0; lvk = LV_NONE;
	return 0;
}
fn prologue() { lit(ZFP); op(O_LD); fframe = hole(); op(O_SUB); lit(ZFP); op(O_ST); return 0; }
fn epilogue()
{
	lit(0);
	fixall(epichain, here);
	lit(ZFP); op(O_LD); lit(fslots); op(O_ADD); lit(ZFP); op(O_ST); op(O_RET);
	setlit(fframe, fslots);
	infn = 0;
	nloc = lbase;
	return 0;
}
fn body()
{
	expect(s_lb);
	while (!is_op(s_rb)) { if (tk == T_EOF) die("missing } at the end of a function"); stmt(); }
	next();
	unused_check(lbase);
	if (fchk && live) { exit_vars(1, 1); if (fret) cerr("a -> u function has to end with a return"); }
	return 0;
}
fn fndef(chk)
{
	var n, s, np = 0, tags = 0, t, ret = 0, sig, i, pn[24], pt[24];
	next();
	n = name();
	s = lookup(n);
	if (s < 0 || s < ubase || skind[s] != K_FN || (sflag[s] & F_DEF)) { s = addsym(n, K_FN, 0); sflag[s] = 0; }
	expect(s_lp);
	if (!is_op(s_rp)) {
		while (1) {
			t = 0;
			if (tk == T_ID && (tv == s_m || tv == s_d)) {
				t = 1; if (tv == s_d) t = 2;
				pn[np] = tv;
				next();
				if (tk == T_ID) pn[np] = name(); else t = 0;	// a parameter called m or d
			} else pn[np] = name();
			if (np >= 12 && t) die("only the first 12 parameters can be tagged");
			pt[np] = t;
			if (np < 12) tags = tags + (t << (np + np));
			np++;
			if (np >= 24) die("too many parameters");
			if (!accept(s_comma)) break;
		}
	}
	expect(s_rp);
	if (accept(s_arrow)) { if (!is_id(s_u)) die("the only return tag is -> u"); next(); ret = 1; }
	sig = ret + np + np + tags * 64;
	if (sflag[s] & F_SIG) { if (ssig[s] != sig) dien(n, "doesn't match its earlier declaration"); }
	else if ((sflag[s] & F_UNTYPED) && (tags || ret)) dien(n, "was called before its tags were declared; put a prototype above the first call");
	ssig[s] = sig;
	sflag[s] = sflag[s] | F_SIG;
	if (accept(s_semi)) return s;
	if (sflag[s] & F_DEF) dien(n, "is defined twice");
	sval[s] = here;
	sflag[s] = sflag[s] | F_DEF;
	fixall(sfix[s], here); sfix[s] = 0;
	fn_begin(chk, ret);
	prologue();
	i = 0;
	while (i < np) {
		t = newloc(pn[i]); fslots++;
		if (fchk && pt[i] == 1) lstate[t] = S_BORROW;
		if (fchk && pt[i] == 2) { lstate[t] = S_M; lown[t] = 1; }
		i++;
	}
	i = np;
	while (i) { i--; laddr(i); op(O_ST); }
	body();
	epilogue();
	return s;
}
fn gvar()
{
	var n, a, k;
	next();
	while (1) {
		n = name();
		if (accept(s_lk)) {
			k = cexpr(); expect(s_rk);
			addsym(n, K_GARR, here);
			while (k) { emit(0); k--; }
		} else {
			a = here;
			addsym(n, K_GVAR, a);
			emit(0);
			if (accept(s_eq)) {
				if (tk == T_STR) { *(a + hdelta) = here; k = tv; while (*k) { emit(*k); k++; } emit(0); next(); }
				else *(a + hdelta) = cexpr();
			}
		}
		if (!accept(s_comma)) break;
	}
	expect(s_semi);
	return 0;
}
fn gconst()
{
	var n;
	next();
	while (1) { n = name(); expect(s_eq); addsym(n, K_CONST, cexpr()); if (!accept(s_comma)) break; }
	expect(s_semi);
	return 0;
}
fn topitem()
{
	var chk = 1, imm = 0, s, k;
	if (is_id(s_unchecked)) {
		next();
		if (accept(s_semi)) { check_on = 0; return 0; }	// unchecked; switches the analyzer off from here on
		chk = 0;
	}
	if (is_id(s_immediate)) { next(); imm = 1; }
	if (is_id(s_fn)) {
		s = fndef(chk);
		if (imm) {
			if (hdelta) die("parse words can't be defined while building an image");
			k = addsym(sname[s], K_KW, sval[s]);
			sflag[k] = F_DEF | F_STMT | F_EXPR | F_TOP;
		}
		return 0;
	}
	if (!chk || imm) die("expected fn");
	if (is_id(s_var)) return gvar();
	if (is_id(s_const)) return gconst();
	if (tk == T_ID) {
		s = lookup(tv);
		if (s >= 0 && skind[s] == K_KW && (sflag[s] & F_TOP)) { kwcall(s, 0); return 0; }
	}
	die("expected fn, var or const");
	return 0;
}
fn unit_top() { while (tk != T_EOF) topitem(); return 0; }
fn unit_end(from)
{
	var i = from;
	while (i < nsym) {
		if (skind[i] == K_FN && !(sflag[i] & F_DEF) && sfix[i]) dien(sname[i], "is used but never defined");
		i++;
	}
	return 0;
}

// compile a token list as the body of a new function, or (top) as top-level
// declarations. returns the entry address of the function.
unchecked fn compile_list(m q, top)
{
	var hop = -1, entry = 0, from = nsym;
	ctx_push();
	if (infn) { hop = hole(); op(O_JMP); }
	src_push(1, q, 0, 0);
	next();
	if (top) unit_top();
	else {
		entry = here;
		fn_begin(1, 0);
		prologue();
		while (tk != T_EOF) stmt();
		unused_check(lbase);
		if (fchk && live) exit_vars(1, 1);
		epilogue();
	}
	src_pop();
	unit_end(from);
	if (hop >= 0) setlit(hop, here);
	if (here > ptop) ptop = here;
	ctx_pop();
	return entry;
}
fn compile(m q) { return compile_list(q, 0); }
fn load(m q) { compile_list(q, 1); return 0; }
fn eval(m q) { var f = compile_list(q, 0); return f(); }
fn evals(s) { var q = tokens(s), r = eval(q); free(q as d); return r; }

// ---- symbol blob ----
// an image ends with its own symbol table so the genome knows its names:
// kind, value, signature, name chars, 0 ... then a 0 kind.
fn blob_emit(from)
{
	var i = from, p;
	while (i < nsym) {
		if (skind[i] >= K_FN && skind[i] <= K_CONST) {
			emit(skind[i]); emit(sval[i]); emit(ssig[i]);
			p = sname[i];
			while (*p) { emit(*p); p++; }
			emit(0);
		}
		i++;
	}
	emit(0);
	return 0;
}
fn blob_load(p)
{
	var s, n;
	while (*p) {
		n = intern(p + 3);
		s = addsym(n, p[0], p[1]);
		ssig[s] = p[2];
		sflag[s] = F_DEF | F_SIG;
		p = p + 3 + strlen(p + 3) + 1;
	}
	return 0;
}
// compile the rest of stdin as a genome image that will run at org, writing
// it to dst. only the source's own names are visible while it compiles.
// returns the image length in words.
fn build_image(org, dst)
{
	var sh = here, sd = hdelta, sl = hlimit, sub = ubase, svl = vislo, sns = nsym, n;
	ubase = nsym; vislo = nsym;
	here = org; hdelta = dst - org; hlimit = org + 0x30000;
	lit(FTOP); lit(ZFP); op(O_ST); fnref(fwdfn(s_start)); op(O_JMP); emit(0); emit(0);
	src_push(0, 0, 0, 0);
	next();
	unit_top();
	unit_end(ubase);
	src_pop();
	*(dst + 5) = here;
	blob_emit(ubase);
	*(dst + 6) = here;
	n = here - org;
	popsyms(sns);
	ubase = sub; vislo = svl; here = sh; hdelta = sd; hlimit = sl;
	return n;
}

// ---- setup ----
fn gc_roots()
{
	markrange(0, ptop);
	if (!hdelta && here > ptop) markrange(ptop, here);	// globals of a unit still compiling
	markrange(GORG, GORG[6]);
	markrange(R_SRC, R_SRC + 400);
	markrange(*ZFP, FTOP);
	markrange(DSLO, DSHI);
	return 0;
}
fn zc_init()
{
	pooltop = R_POOL;
	wfill(R_IH, 0, IHN);
	nsym = 0; nfixu = 0; fixfree = 0; nbin = 0; nun = 0; nasg = 0; nkop = 0; seqtop = 0;
	lsp = 0; ctxsp = 0; snaptop = 0; nloc = 0; lbase = 0;
	s_lp = intern("("); s_rp = intern(")"); s_lb = intern("{"); s_rb = intern("}");
	s_lk = intern("["); s_rk = intern("]"); s_comma = intern(","); s_semi = intern(";");
	s_eq = intern("="); s_arrow = intern("->"); s_inc = intern("++"); s_dec = intern("--");
	s_star = intern("*"); s_amp = intern("&"); s_colon = intern(":"); s_hash = intern("#");
	s_minus = intern("-"); s_andand = intern("&&"); s_oror = intern("||");
	s_fn = intern("fn"); s_var = intern("var"); s_const = intern("const"); s_else = intern("else");
	s_as = intern("as"); s_unchecked = intern("unchecked"); s_immediate = intern("immediate");
	s_m = intern("m"); s_d = intern("d"); s_u = intern("u");
	s_start = intern("start"); s_main = intern("main"); s_free = intern("free");
	s_own = intern("own"); s_qnew = intern("qnew");
	return 0;
}
// operators and keywords. these are plain tables in memory: a program can
// add operators, change precedences or replace keywords with its own.
fn zc_tables()
{
	add_unop("!", "0 $ 0 ~ - | 31 > 1 +");	// index 0
	add_unop("!!", "0 $ 0 ~ - | 31 > 0 ~ -");	// index 1: normalize to 0 or 1
	add_unop("~", "-1 ^");				// index 2
	add_unop("-", "0 ~ -");
	add_binop("*", 10, "*");			// the first few indexes are used by cexpr
	add_binop("/", 10, "zdiv c");
	add_binop("%", 10, "zmod c");
	add_binop("+", 9, "+");				// 3
	add_binop("-", 9, "-");				// 4
	add_binop("<<", 8, "zshl c");			// 5
	add_binop(">>", 8, ">");			// 6
	add_binop("<", 7, "<");
	add_binop(">", 7, "~ <");
	add_binop("<=", 7, "~ < 1 ^");
	add_binop(">=", 7, "< 1 ^");
	add_binop("==", 6, "- 0 $ 0 ~ - | 31 > 1 +");
	add_binop("!=", 6, "- 0 $ 0 ~ - | 31 > 0 ~ -");
	add_binop("&", 5, "&");				// 13
	add_binop("^", 4, "^");
	add_binop("|", 3, "|");				// 15
	add_binop("&&", -1, 0);
	add_binop("||", -2, 0);
	addkop(s_eq); addkop(s_arrow); addkop(s_inc); addkop(s_dec);
	add_kw("var", kw_var, F_STMT);
	add_kw("if", kw_if, F_STMT);
	add_kw("while", kw_while, F_STMT);
	add_kw("for", kw_for, F_STMT);
	add_kw("break", kw_break, F_STMT);
	add_kw("continue", kw_continue, F_STMT);
	add_kw("return", kw_return, F_STMT);
	add_kw("unchecked", kw_unchecked, F_STMT);
	add_kw("asm", kw_asm, F_STMT | F_EXPR);
	add_kw("quote", kw_quote, F_EXPR);
	return 0;
}
fn start()
{
	var s, f;
	heap_init();
	zc_init();
	blob_load(GORG[5]);
	zc_tables();
	here = 0; hdelta = 0; hlimit = HEAP_LO; ptop = 0;
	ubase = nsym; vislo = 0;
	src_push(0, 0, 0, 0);
	next();
	unit_top();
	unit_end(ubase);
	if (here > ptop) ptop = here;
	s = lookup(s_main);
	if (s >= 0 && skind[s] == K_FN && (sflag[s] & F_DEF)) { f = sval[s]; f(); }
	halt();
	return 0;
}