Re-write of eqn(7) parser and MathML output.

This adds parser-level support for the grammar described by the eqn
second-edition technical paper, "Typesetting Mathematics — User's Guide"
(Kernighan, Cherry).
The reason for this re-write is the grouping rules, which were not
possible given the existing implementation.
The re-write has also considerably simplified the HTML (and, if it ever
is completed, terminal) front-end.

1 files changed, 741 insertions, 612 deletions

diff --git a/eqn.c b/eqn.c
index 7bb956d5..c2e7aed2 100644
--- a/eqn.c
+++ b/eqn.c
@@ -1,4 +1,4 @@
-/*	$Id: eqn.c,v 1.47 2014/09/28 14:05:11 kristaps Exp $ */
+/*	$Id: eqn.c,v 1.48 2014/10/10 08:44:24 kristaps Exp $ */
 /*
  * Copyright (c) 2011 Kristaps Dzonsons <kristaps@bsd.lv>
  *
@@ -30,14 +30,111 @@
 #include "libmandoc.h"
 #include "libroff.h"
 
+#define	EQN_MSG(t, x) \
+	mandoc_msg((t), (x)->parse, (x)->eqn.ln, (x)->eqn.pos, NULL)
 #define	EQN_NEST_MAX	 128 /* maximum nesting of defines */
-#define	EQN_MSG(t, x)	 mandoc_msg((t), (x)->parse, (x)->eqn.ln, (x)->eqn.pos, NULL)
+#define	STRNEQ(p1, sz1, p2, sz2) \
+	((sz1) == (sz2) && 0 == strncmp((p1), (p2), (sz1)))
+#define	EQNSTREQ(x, p, sz) \
+	STRNEQ((x)->name, (x)->sz, (p), (sz))
 
-enum	eqn_rest {
-	EQN_DESCOPE,
-	EQN_ERR,
-	EQN_OK,
-	EQN_EOF
+enum	eqn_tok {
+	EQN_TOK_DYAD = 0,
+	EQN_TOK_VEC,
+	EQN_TOK_UNDER,
+	EQN_TOK_BAR,
+	EQN_TOK_TILDE,
+	EQN_TOK_HAT,
+	EQN_TOK_DOT,
+	EQN_TOK_DOTDOT,
+	EQN_TOK_FWD,
+	EQN_TOK_BACK,
+	EQN_TOK_DOWN,
+	EQN_TOK_UP,
+	EQN_TOK_FAT,
+	EQN_TOK_ROMAN,
+	EQN_TOK_ITALIC,
+	EQN_TOK_BOLD,
+	EQN_TOK_SIZE,
+	EQN_TOK_SUB,
+	EQN_TOK_SUP,
+	EQN_TOK_SQRT,
+	EQN_TOK_OVER,
+	EQN_TOK_FROM,
+	EQN_TOK_TO,
+	EQN_TOK_BRACE_OPEN,
+	EQN_TOK_BRACE_CLOSE,
+	EQN_TOK_GSIZE,
+	EQN_TOK_GFONT,
+	EQN_TOK_MARK,
+	EQN_TOK_LINEUP,
+	EQN_TOK_LEFT,
+	EQN_TOK_RIGHT,
+	EQN_TOK_PILE,
+	EQN_TOK_LPILE,
+	EQN_TOK_RPILE,
+	EQN_TOK_CPILE,
+	EQN_TOK_MATRIX,
+	EQN_TOK_CCOL,
+	EQN_TOK_LCOL,
+	EQN_TOK_RCOL,
+	EQN_TOK_DELIM,
+	EQN_TOK_DEFINE,
+	EQN_TOK_TDEFINE,
+	EQN_TOK_NDEFINE,
+	EQN_TOK_UNDEF,
+	EQN_TOK_EOF,
+	EQN_TOK_ABOVE,
+	EQN_TOK__MAX
+};
+
+static	const char *eqn_toks[EQN_TOK__MAX] = {
+	"dyad", /* EQN_TOK_DYAD */
+	"vec", /* EQN_TOK_VEC */
+	"under", /* EQN_TOK_UNDER */
+	"bar", /* EQN_TOK_BAR */
+	"tilde", /* EQN_TOK_TILDE */
+	"hat", /* EQN_TOK_HAT */
+	"dot", /* EQN_TOK_DOT */
+	"dotdot", /* EQN_TOK_DOTDOT */
+	"fwd", /* EQN_TOK_FWD * */
+	"back", /* EQN_TOK_BACK */
+	"down", /* EQN_TOK_DOWN */
+	"up", /* EQN_TOK_UP */
+	"fat", /* EQN_TOK_FAT */
+	"roman", /* EQN_TOK_ROMAN */
+	"italic", /* EQN_TOK_ITALIC */
+	"bold", /* EQN_TOK_BOLD */
+	"size", /* EQN_TOK_SIZE */
+	"sub", /* EQN_TOK_SUB */
+	"sup", /* EQN_TOK_SUP */
+	"sqrt", /* EQN_TOK_SQRT */
+	"over", /* EQN_TOK_OVER */
+	"from", /* EQN_TOK_FROM */
+	"to", /* EQN_TOK_TO */
+	"{", /* EQN_TOK_BRACE_OPEN */
+	"}", /* EQN_TOK_BRACE_CLOSE */
+	"gsize", /* EQN_TOK_GSIZE */
+	"gfont", /* EQN_TOK_GFONT */
+	"mark", /* EQN_TOK_MARK */
+	"lineup", /* EQN_TOK_LINEUP */
+	"left", /* EQN_TOK_LEFT */
+	"right", /* EQN_TOK_RIGHT */
+	"pile", /* EQN_TOK_PILE */
+	"lpile", /* EQN_TOK_LPILE */
+	"rpile", /* EQN_TOK_RPILE */
+	"cpile", /* EQN_TOK_CPILE */
+	"matrix", /* EQN_TOK_MATRIX */
+	"ccol", /* EQN_TOK_CCOL */
+	"lcol", /* EQN_TOK_LCOL */
+	"rcol", /* EQN_TOK_RCOL */
+	"delim", /* EQN_TOK_DELIM */
+	"define", /* EQN_TOK_DEFINE */
+	"tdefine", /* EQN_TOK_TDEFINE */
+	"ndefine", /* EQN_TOK_NDEFINE */
+	"undef", /* EQN_TOK_UNDEF */
+	NULL, /* EQN_TOK_EOF */
+	"above", /* EQN_TOK_ABOVE */
 };
 
 enum	eqn_symt {
@@ -103,183 +200,73 @@ enum	eqn_symt {
 	EQNSYM__MAX
 };
 
-enum	eqnpartt {
-	EQN_DEFINE = 0,
-	EQN_NDEFINE,
-	EQN_TDEFINE,
-	EQN_SET,
-	EQN_UNDEF,
-	EQN_GFONT,
-	EQN_GSIZE,
-	EQN_BACK,
-	EQN_FWD,
-	EQN_UP,
-	EQN_DOWN,
-	EQN__MAX
-};
-
-struct	eqnstr {
-	const char	*name;
-	size_t		 sz;
-};
-
-#define	STRNEQ(p1, sz1, p2, sz2) \
-	((sz1) == (sz2) && 0 == strncmp((p1), (p2), (sz1)))
-#define	EQNSTREQ(x, p, sz) \
-	STRNEQ((x)->name, (x)->sz, (p), (sz))
-
-struct	eqnpart {
-	struct eqnstr	 str;
-	int		(*fp)(struct eqn_node *);
-};
-
 struct	eqnsym {
-	struct eqnstr	 str;
+	const char	*str;
 	const char	*sym;
 };
 
-static	enum eqn_rest	 eqn_box(struct eqn_node *, struct eqn_box *);
-static	struct eqn_box	*eqn_box_alloc(struct eqn_node *,
-				struct eqn_box *);
-static	void		 eqn_box_free(struct eqn_box *);
-static	struct eqn_def	*eqn_def_find(struct eqn_node *,
-				const char *, size_t);
-static	int		 eqn_do_gfont(struct eqn_node *);
-static	int		 eqn_do_gsize(struct eqn_node *);
-static	int		 eqn_do_define(struct eqn_node *);
-static	int		 eqn_do_ign1(struct eqn_node *);
-static	int		 eqn_do_ign2(struct eqn_node *);
-static	int		 eqn_do_tdefine(struct eqn_node *);
-static	int		 eqn_do_undef(struct eqn_node *);
-static	enum eqn_rest	 eqn_eqn(struct eqn_node *, struct eqn_box *);
-static	enum eqn_rest	 eqn_list(struct eqn_node *, struct eqn_box *);
-static	enum eqn_rest	 eqn_matrix(struct eqn_node *, struct eqn_box *);
-static	const char	*eqn_nexttok(struct eqn_node *, size_t *);
-static	const char	*eqn_nextrawtok(struct eqn_node *, size_t *);
-static	const char	*eqn_next(struct eqn_node *,
-				char, size_t *, int);
-static	void		 eqn_rewind(struct eqn_node *);
-
-static	const struct eqnpart eqnparts[EQN__MAX] = {
-	{ { "define", 6 }, eqn_do_define }, /* EQN_DEFINE */
-	{ { "ndefine", 7 }, eqn_do_define }, /* EQN_NDEFINE */
-	{ { "tdefine", 7 }, eqn_do_tdefine }, /* EQN_TDEFINE */
-	{ { "set", 3 }, eqn_do_ign2 }, /* EQN_SET */
-	{ { "undef", 5 }, eqn_do_undef }, /* EQN_UNDEF */
-	{ { "gfont", 5 }, eqn_do_gfont }, /* EQN_GFONT */
-	{ { "gsize", 5 }, eqn_do_gsize }, /* EQN_GSIZE */
-	{ { "back", 4 }, eqn_do_ign1 }, /* EQN_BACK */
-	{ { "fwd", 3 }, eqn_do_ign1 }, /* EQN_FWD */
-	{ { "up", 2 }, eqn_do_ign1 }, /* EQN_UP */
-	{ { "down", 4 }, eqn_do_ign1 }, /* EQN_DOWN */
-};
-
-static	const struct eqnstr eqnmarks[EQNMARK__MAX] = {
-	{ "", 0 }, /* EQNMARK_NONE */
-	{ "dot", 3 }, /* EQNMARK_DOT */
-	{ "dotdot", 6 }, /* EQNMARK_DOTDOT */
-	{ "hat", 3 }, /* EQNMARK_HAT */
-	{ "tilde", 5 }, /* EQNMARK_TILDE */
-	{ "vec", 3 }, /* EQNMARK_VEC */
-	{ "dyad", 4 }, /* EQNMARK_DYAD */
-	{ "bar", 3 }, /* EQNMARK_BAR */
-	{ "under", 5 }, /* EQNMARK_UNDER */
-};
-
-static	const struct eqnstr eqnfonts[EQNFONT__MAX] = {
-	{ "", 0 }, /* EQNFONT_NONE */
-	{ "roman", 5 }, /* EQNFONT_ROMAN */
-	{ "bold", 4 }, /* EQNFONT_BOLD */
-	{ "fat", 3 }, /* EQNFONT_FAT */
-	{ "italic", 6 }, /* EQNFONT_ITALIC */
-};
-
-static	const struct eqnstr eqnposs[EQNPOS__MAX] = {
-	{ NULL, 0 }, /* EQNPOS_NONE */
-	{ "over", 4 }, /* EQNPOS_OVER */
-	{ "sup", 3 }, /* EQNPOS_SUP */
-	{ NULL, 0 }, /* EQNPOS_SUPSUB */
-	{ "sub", 3 }, /* EQNPOS_SUB */
-	{ "to", 2 }, /* EQNPOS_TO */
-	{ "from", 4 }, /* EQNPOS_FROM */
-	{ NULL, 0 }, /* EQNPOS_FROMTO */
-};
-
-static	const struct eqnstr eqnpiles[EQNPILE__MAX] = {
-	{ "", 0 }, /* EQNPILE_NONE */
-	{ "pile", 4 }, /* EQNPILE_PILE */
-	{ "cpile", 5 }, /* EQNPILE_CPILE */
-	{ "rpile", 5 }, /* EQNPILE_RPILE */
-	{ "lpile", 5 }, /* EQNPILE_LPILE */
-	{ "col", 3 }, /* EQNPILE_COL */
-	{ "ccol", 4 }, /* EQNPILE_CCOL */
-	{ "rcol", 4 }, /* EQNPILE_RCOL */
-	{ "lcol", 4 }, /* EQNPILE_LCOL */
-};
-
 static	const struct eqnsym eqnsyms[EQNSYM__MAX] = {
-	{ { "alpha", 5 }, "*a" }, /* EQNSYM_alpha */
-	{ { "beta", 4 }, "*b" }, /* EQNSYM_beta */
-	{ { "chi", 3 }, "*x" }, /* EQNSYM_chi */
-	{ { "delta", 5 }, "*d" }, /* EQNSYM_delta */
-	{ { "epsilon", 7 }, "*e" }, /* EQNSYM_epsilon */
-	{ { "eta", 3 }, "*y" }, /* EQNSYM_eta */
-	{ { "gamma", 5 }, "*g" }, /* EQNSYM_gamma */
-	{ { "iota", 4 }, "*i" }, /* EQNSYM_iota */
-	{ { "kappa", 5 }, "*k" }, /* EQNSYM_kappa */
-	{ { "lambda", 6 }, "*l" }, /* EQNSYM_lambda */
-	{ { "mu", 2 }, "*m" }, /* EQNSYM_mu */
-	{ { "nu", 2 }, "*n" }, /* EQNSYM_nu */
-	{ { "omega", 5 }, "*w" }, /* EQNSYM_omega */
-	{ { "omicron", 7 }, "*o" }, /* EQNSYM_omicron */
-	{ { "phi", 3 }, "*f" }, /* EQNSYM_phi */
-	{ { "pi", 2 }, "*p" }, /* EQNSYM_pi */
-	{ { "psi", 2 }, "*q" }, /* EQNSYM_psi */
-	{ { "rho", 3 }, "*r" }, /* EQNSYM_rho */
-	{ { "sigma", 5 }, "*s" }, /* EQNSYM_sigma */
-	{ { "tau", 3 }, "*t" }, /* EQNSYM_tau */
-	{ { "theta", 5 }, "*h" }, /* EQNSYM_theta */
-	{ { "upsilon", 7 }, "*u" }, /* EQNSYM_upsilon */
-	{ { "xi", 2 }, "*c" }, /* EQNSYM_xi */
-	{ { "zeta", 4 }, "*z" }, /* EQNSYM_zeta */
-	{ { "DELTA", 5 }, "*D" }, /* EQNSYM_DELTA */
-	{ { "GAMMA", 5 }, "*G" }, /* EQNSYM_GAMMA */
-	{ { "LAMBDA", 6 }, "*L" }, /* EQNSYM_LAMBDA */
-	{ { "OMEGA", 5 }, "*W" }, /* EQNSYM_OMEGA */
-	{ { "PHI", 3 }, "*F" }, /* EQNSYM_PHI */
-	{ { "PI", 2 }, "*P" }, /* EQNSYM_PI */
-	{ { "PSI", 3 }, "*Q" }, /* EQNSYM_PSI */
-	{ { "SIGMA", 5 }, "*S" }, /* EQNSYM_SIGMA */
-	{ { "THETA", 5 }, "*H" }, /* EQNSYM_THETA */
-	{ { "UPSILON", 7 }, "*U" }, /* EQNSYM_UPSILON */
-	{ { "XI", 2 }, "*C" }, /* EQNSYM_XI */
-	{ { "inter", 5 }, "ca" }, /* EQNSYM_inter */
-	{ { "union", 5 }, "cu" }, /* EQNSYM_union */
-	{ { "prod", 4 }, "product" }, /* EQNSYM_prod */
-	{ { "int", 3 }, "integral" }, /* EQNSYM_int */
-	{ { "sum", 3 }, "sum" }, /* EQNSYM_sum */
-	{ { "grad", 4 }, "gr" }, /* EQNSYM_grad */
-	{ { "del", 3 }, "gr" }, /* EQNSYM_del */
-	{ { "times", 5 }, "mu" }, /* EQNSYM_times */
-	{ { "cdot", 4 }, "pc" }, /* EQNSYM_cdot */
-	{ { "nothing", 7 }, "&" }, /* EQNSYM_nothing */
-	{ { "approx", 6 }, "~~" }, /* EQNSYM_approx */
-	{ { "prime", 5 }, "aq" }, /* EQNSYM_prime */
-	{ { "half", 4 }, "12" }, /* EQNSYM_half */
-	{ { "partial", 7 }, "pd" }, /* EQNSYM_partial */
-	{ { "inf", 3 }, "if" }, /* EQNSYM_inf */
-	{ { ">>", 2 }, ">>" }, /* EQNSYM_muchgreat */
-	{ { "<<", 2 }, "<<" }, /* EQNSYM_muchless */
-	{ { "<-", 2 }, "<-" }, /* EQNSYM_larrow */
-	{ { "->", 2 }, "->" }, /* EQNSYM_rarrow */
-	{ { "+-", 2 }, "+-" }, /* EQNSYM_pm */
-	{ { "!=", 2 }, "!=" }, /* EQNSYM_nequal */
-	{ { "==", 2 }, "==" }, /* EQNSYM_equiv */
-	{ { "<=", 2 }, "<=" }, /* EQNSYM_lessequal */
-	{ { ">=", 2 }, ">=" }, /* EQNSYM_moreequal */
+	{ "alpha", "*a" }, /* EQNSYM_alpha */
+	{ "beta", "*b" }, /* EQNSYM_beta */
+	{ "chi", "*x" }, /* EQNSYM_chi */
+	{ "delta", "*d" }, /* EQNSYM_delta */
+	{ "epsilon", "*e" }, /* EQNSYM_epsilon */
+	{ "eta", "*y" }, /* EQNSYM_eta */
+	{ "gamma", "*g" }, /* EQNSYM_gamma */
+	{ "iota", "*i" }, /* EQNSYM_iota */
+	{ "kappa", "*k" }, /* EQNSYM_kappa */
+	{ "lambda", "*l" }, /* EQNSYM_lambda */
+	{ "mu", "*m" }, /* EQNSYM_mu */
+	{ "nu", "*n" }, /* EQNSYM_nu */
+	{ "omega", "*w" }, /* EQNSYM_omega */
+	{ "omicron", "*o" }, /* EQNSYM_omicron */
+	{ "phi", "*f" }, /* EQNSYM_phi */
+	{ "pi", "*p" }, /* EQNSYM_pi */
+	{ "psi", "*q" }, /* EQNSYM_psi */
+	{ "rho", "*r" }, /* EQNSYM_rho */
+	{ "sigma", "*s" }, /* EQNSYM_sigma */
+	{ "tau", "*t" }, /* EQNSYM_tau */
+	{ "theta", "*h" }, /* EQNSYM_theta */
+	{ "upsilon", "*u" }, /* EQNSYM_upsilon */
+	{ "xi", "*c" }, /* EQNSYM_xi */
+	{ "zeta", "*z" }, /* EQNSYM_zeta */
+	{ "DELTA", "*D" }, /* EQNSYM_DELTA */
+	{ "GAMMA", "*G" }, /* EQNSYM_GAMMA */
+	{ "LAMBDA", "*L" }, /* EQNSYM_LAMBDA */
+	{ "OMEGA", "*W" }, /* EQNSYM_OMEGA */
+	{ "PHI", "*F" }, /* EQNSYM_PHI */
+	{ "PI", "*P" }, /* EQNSYM_PI */
+	{ "PSI", "*Q" }, /* EQNSYM_PSI */
+	{ "SIGMA", "*S" }, /* EQNSYM_SIGMA */
+	{ "THETA", "*H" }, /* EQNSYM_THETA */
+	{ "UPSILON", "*U" }, /* EQNSYM_UPSILON */
+	{ "XI", "*C" }, /* EQNSYM_XI */
+	{ "inter", "ca" }, /* EQNSYM_inter */
+	{ "union", "cu" }, /* EQNSYM_union */
+	{ "prod", "product" }, /* EQNSYM_prod */
+	{ "int", "integral" }, /* EQNSYM_int */
+	{ "sum", "sum" }, /* EQNSYM_sum */
+	{ "grad", "gr" }, /* EQNSYM_grad */
+	{ "del", "gr" }, /* EQNSYM_del */
+	{ "times", "mu" }, /* EQNSYM_times */
+	{ "cdot", "pc" }, /* EQNSYM_cdot */
+	{ "nothing", "&" }, /* EQNSYM_nothing */
+	{ "approx", "~~" }, /* EQNSYM_approx */
+	{ "prime", "aq" }, /* EQNSYM_prime */
+	{ "half", "12" }, /* EQNSYM_half */
+	{ "partial", "pd" }, /* EQNSYM_partial */
+	{ "inf", "if" }, /* EQNSYM_inf */
+	{ ">>", ">>" }, /* EQNSYM_muchgreat */
+	{ "<<", "<<" }, /* EQNSYM_muchless */
+	{ "<-", "<-" }, /* EQNSYM_larrow */
+	{ "->", "->" }, /* EQNSYM_rarrow */
+	{ "+-", "+-" }, /* EQNSYM_pm */
+	{ "!=", "!=" }, /* EQNSYM_nequal */
+	{ "==", "==" }, /* EQNSYM_equiv */
+	{ "<=", "<=" }, /* EQNSYM_lessequal */
+	{ ">=", ">=" }, /* EQNSYM_moreequal */
 };
 
-
 enum rofferr
 eqn_read(struct eqn_node **epp, int ln,
 		const char *p, int pos, int *offs)
@@ -353,386 +340,27 @@ eqn_alloc(const char *name, int pos, int line, struct mparse *parse)
 	return(p);
 }
 
-enum rofferr
-eqn_end(struct eqn_node **epp)
-{
-	struct eqn_node	*ep;
-	struct eqn_box	*root;
-	enum eqn_rest	 c;
-
-	ep = *epp;
-	*epp = NULL;
-
-	ep->eqn.root = mandoc_calloc(1, sizeof(struct eqn_box));
-
-	root = ep->eqn.root;
-	root->type = EQN_ROOT;
-
-	if (0 == ep->sz)
-		return(ROFF_IGN);
-
-	if (EQN_DESCOPE == (c = eqn_eqn(ep, root))) {
-		EQN_MSG(MANDOCERR_EQNNSCOPE, ep);
-		c = EQN_ERR;
-	}
-
-	return(EQN_EOF == c ? ROFF_EQN : ROFF_IGN);
-}
-
-static enum eqn_rest
-eqn_eqn(struct eqn_node *ep, struct eqn_box *last)
-{
-	struct eqn_box	*bp;
-	enum eqn_rest	 c;
-
-	bp = eqn_box_alloc(ep, last);
-	bp->type = EQN_SUBEXPR;
-
-	while (EQN_OK == (c = eqn_box(ep, bp)))
-		/* Spin! */ ;
-
-	return(c);
-}
-
-static enum eqn_rest
-eqn_matrix(struct eqn_node *ep, struct eqn_box *last)
-{
-	struct eqn_box	*bp;
-	const char	*start;
-	size_t		 sz;
-	enum eqn_rest	 c;
-
-	bp = eqn_box_alloc(ep, last);
-	bp->type = EQN_MATRIX;
-
-	if (NULL == (start = eqn_nexttok(ep, &sz))) {
-		EQN_MSG(MANDOCERR_EQNEOF, ep);
-		return(EQN_ERR);
-	}
-	if ( ! STRNEQ(start, sz, "{", 1)) {
-		EQN_MSG(MANDOCERR_EQNSYNT, ep);
-		return(EQN_ERR);
-	}
-
-	while (EQN_OK == (c = eqn_box(ep, bp)))
-		switch (bp->last->pile) {
-		case EQNPILE_LCOL:
-			/* FALLTHROUGH */
-		case EQNPILE_CCOL:
-			/* FALLTHROUGH */
-		case EQNPILE_RCOL:
-			continue;
-		default:
-			EQN_MSG(MANDOCERR_EQNSYNT, ep);
-			return(EQN_ERR);
-		};
-
-	if (EQN_DESCOPE != c) {
-		if (EQN_EOF == c)
-			EQN_MSG(MANDOCERR_EQNEOF, ep);
-		return(EQN_ERR);
-	}
-
-	eqn_rewind(ep);
-	start = eqn_nexttok(ep, &sz);
-	assert(start);
-	if (STRNEQ(start, sz, "}", 1))
-		return(EQN_OK);
-
-	EQN_MSG(MANDOCERR_EQNBADSCOPE, ep);
-	return(EQN_ERR);
-}
-
-static enum eqn_rest
-eqn_list(struct eqn_node *ep, struct eqn_box *last)
-{
-	struct eqn_box	*bp;
-	const char	*start;
-	size_t		 sz;
-	enum eqn_rest	 c;
-
-	bp = eqn_box_alloc(ep, last);
-	bp->type = EQN_LIST;
-
-	if (NULL == (start = eqn_nexttok(ep, &sz))) {
-		EQN_MSG(MANDOCERR_EQNEOF, ep);
-		return(EQN_ERR);
-	}
-	if ( ! STRNEQ(start, sz, "{", 1)) {
-		EQN_MSG(MANDOCERR_EQNSYNT, ep);
-		return(EQN_ERR);
-	}
-
-	while (EQN_DESCOPE == (c = eqn_eqn(ep, bp))) {
-		eqn_rewind(ep);
-		start = eqn_nexttok(ep, &sz);
-		assert(start);
-		if ( ! STRNEQ(start, sz, "above", 5))
-			break;
-	}
-
-	if (EQN_DESCOPE != c) {
-		if (EQN_ERR != c)
-			EQN_MSG(MANDOCERR_EQNSCOPE, ep);
-		return(EQN_ERR);
-	}
-
-	eqn_rewind(ep);
-	start = eqn_nexttok(ep, &sz);
-	assert(start);
-	if (STRNEQ(start, sz, "}", 1))
-		return(EQN_OK);
-
-	EQN_MSG(MANDOCERR_EQNBADSCOPE, ep);
-	return(EQN_ERR);
-}
-
-static enum eqn_rest
-eqn_box(struct eqn_node *ep, struct eqn_box *last)
-{
-	size_t		 sz;
-	const char	*start;
-	char		*left;
-	char		 sym[64];
-	enum eqn_rest	 c;
-	int		 i, size;
-	struct eqn_box	*bp;
-
-	if (NULL == (start = eqn_nexttok(ep, &sz)))
-		return(EQN_EOF);
-
-	if (STRNEQ(start, sz, "}", 1))
-		return(EQN_DESCOPE);
-	else if (STRNEQ(start, sz, "right", 5))
-		return(EQN_DESCOPE);
-	else if (STRNEQ(start, sz, "above", 5))
-		return(EQN_DESCOPE);
-	else if (STRNEQ(start, sz, "mark", 4))
-		return(EQN_OK);
-	else if (STRNEQ(start, sz, "lineup", 6))
-		return(EQN_OK);
-
-	for (i = 0; i < (int)EQN__MAX; i++) {
-		if ( ! EQNSTREQ(&eqnparts[i].str, start, sz))
-			continue;
-		return((*eqnparts[i].fp)(ep) ? EQN_OK : EQN_ERR);
-	}
-
-	if (STRNEQ(start, sz, "{", 1)) {
-		if (EQN_DESCOPE != (c = eqn_eqn(ep, last))) {
-			if (EQN_ERR != c)
-				EQN_MSG(MANDOCERR_EQNSCOPE, ep);
-			return(EQN_ERR);
-		}
-		eqn_rewind(ep);
-		start = eqn_nexttok(ep, &sz);
-		assert(start);
-		if (STRNEQ(start, sz, "}", 1))
-			return(EQN_OK);
-		EQN_MSG(MANDOCERR_EQNBADSCOPE, ep);
-		return(EQN_ERR);
-	}
-
-	for (i = 0; i < (int)EQNPILE__MAX; i++) {
-		if ( ! EQNSTREQ(&eqnpiles[i], start, sz))
-			continue;
-		if (EQN_OK == (c = eqn_list(ep, last)))
-			last->last->pile = (enum eqn_pilet)i;
-		return(c);
-	}
-
-	if (STRNEQ(start, sz, "matrix", 6))
-		return(eqn_matrix(ep, last));
-
-	if (STRNEQ(start, sz, "left", 4)) {
-		if (NULL == (start = eqn_nexttok(ep, &sz))) {
-			EQN_MSG(MANDOCERR_EQNEOF, ep);
-			return(EQN_ERR);
-		}
-		left = mandoc_strndup(start, sz);
-		c = eqn_eqn(ep, last);
-		if (last->last)
-			last->last->left = left;
-		else
-			free(left);
-		if (EQN_DESCOPE != c)
-			return(c);
-		assert(last->last);
-		eqn_rewind(ep);
-		start = eqn_nexttok(ep, &sz);
-		assert(start);
-		if ( ! STRNEQ(start, sz, "right", 5))
-			return(EQN_DESCOPE);
-		if (NULL == (start = eqn_nexttok(ep, &sz))) {
-			EQN_MSG(MANDOCERR_EQNEOF, ep);
-			return(EQN_ERR);
-		}
-		last->last->right = mandoc_strndup(start, sz);
-		return(EQN_OK);
-	}
-
-	/*
-	 * Positional elements (e.g., over, sub, sup, ...).
-	 */
-	for (i = 0; i < (int)EQNPOS__MAX; i++) {
-		/* Some elements don't have names (are virtual). */
-		if (NULL == eqnposs[i].name)
-			continue;
-		else if ( ! EQNSTREQ(&eqnposs[i], start, sz))
-			continue;
-		if (NULL == last->last) {
-			EQN_MSG(MANDOCERR_EQNSYNT, ep);
-			return(EQN_ERR);
-		}
-		/*
-		 * If we encounter x sub y sup z, then according to the
-		 * eqn manual, we regard this as x subsup y z.
-		 */
-		if (EQNPOS_SUP == i &&
-			NULL != last->last->prev &&
-			EQNPOS_SUB == last->last->prev->pos)
-			last->last->prev->pos = EQNPOS_SUBSUP;
-		else if (EQNPOS_TO == i &&
-			NULL != last->last->prev &&
-			EQNPOS_FROM == last->last->prev->pos)
-			last->last->prev->pos = EQNPOS_FROMTO;
-		else
-			last->last->pos = (enum eqn_post)i;
-
-		if (EQN_EOF == (c = eqn_box(ep, last))) {
-			EQN_MSG(MANDOCERR_EQNEOF, ep);
-			return(EQN_ERR);
-		}
-		return(c);
-	}
-
-	for (i = 0; i < (int)EQNMARK__MAX; i++) {
-		if ( ! EQNSTREQ(&eqnmarks[i], start, sz))
-			continue;
-		if (NULL == last->last) {
-			EQN_MSG(MANDOCERR_EQNSYNT, ep);
-			return(EQN_ERR);
-		}
-		last->last->mark = (enum eqn_markt)i;
-		if (EQN_EOF == (c = eqn_box(ep, last))) {
-			EQN_MSG(MANDOCERR_EQNEOF, ep);
-			return(EQN_ERR);
-		}
-		return(c);
-	}
-
-	for (i = 0; i < (int)EQNFONT__MAX; i++) {
-		if ( ! EQNSTREQ(&eqnfonts[i], start, sz))
-			continue;
-		if (EQN_EOF == (c = eqn_box(ep, last))) {
-			EQN_MSG(MANDOCERR_EQNEOF, ep);
-			return(EQN_ERR);
-		} else if (EQN_OK == c)
-			last->last->font = (enum eqn_fontt)i;
-		return(c);
-	}
-
-	if (STRNEQ(start, sz, "size", 4)) {
-		if (NULL == (start = eqn_nexttok(ep, &sz))) {
-			EQN_MSG(MANDOCERR_EQNEOF, ep);
-			return(EQN_ERR);
-		}
-		size = mandoc_strntoi(start, sz, 10);
-		if (EQN_EOF == (c = eqn_box(ep, last))) {
-			EQN_MSG(MANDOCERR_EQNEOF, ep);
-			return(EQN_ERR);
-		} else if (EQN_OK != c)
-			return(c);
-		last->last->size = size;
-	}
-
-	bp = eqn_box_alloc(ep, last);
-	bp->type = EQN_TEXT;
-	for (i = 0; i < (int)EQNSYM__MAX; i++)
-		if (EQNSTREQ(&eqnsyms[i].str, start, sz)) {
-			sym[63] = '\0';
-			(void)snprintf(sym, 62, "\\[%s]", eqnsyms[i].sym);
-			bp->text = mandoc_strdup(sym);
-			return(EQN_OK);
-		}
-
-	bp->text = mandoc_strndup(start, sz);
-	return(EQN_OK);
-}
-
-void
-eqn_free(struct eqn_node *p)
+/*
+ * Find the key "key" of the give size within our eqn-defined values.
+ */
+static struct eqn_def *
+eqn_def_find(struct eqn_node *ep, const char *key, size_t sz)
 {
 	int		 i;
 
-	eqn_box_free(p->eqn.root);
-
-	for (i = 0; i < (int)p->defsz; i++) {
-		free(p->defs[i].key);
-		free(p->defs[i].val);
-	}
-
-	free(p->eqn.name);
-	free(p->data);
-	free(p->defs);
-	free(p);
-}
-
-static struct eqn_box *
-eqn_box_alloc(struct eqn_node *ep, struct eqn_box *parent)
-{
-	struct eqn_box	*bp;
-
-	bp = mandoc_calloc(1, sizeof(struct eqn_box));
-	bp->parent = parent;
-	bp->size = ep->gsize;
-
-	if (NULL != parent->first) {
-		parent->last->next = bp;
-		bp->prev = parent->last;
-	} else
-		parent->first = bp;
-
-	parent->last = bp;
-	return(bp);
-}
-
-static void
-eqn_box_free(struct eqn_box *bp)
-{
-
-	if (bp->first)
-		eqn_box_free(bp->first);
-	if (bp->next)
-		eqn_box_free(bp->next);
-
-	free(bp->text);
-	free(bp->left);
-	free(bp->right);
-	free(bp);
-}
-
-static const char *
-eqn_nextrawtok(struct eqn_node *ep, size_t *sz)
-{
-
-	return(eqn_next(ep, '"', sz, 0));
-}
-
-static const char *
-eqn_nexttok(struct eqn_node *ep, size_t *sz)
-{
-
-	return(eqn_next(ep, '"', sz, 1));
-}
-
-static void
-eqn_rewind(struct eqn_node *ep)
-{
+	for (i = 0; i < (int)ep->defsz; i++)
+		if (ep->defs[i].keysz && STRNEQ(ep->defs[i].key,
+		    ep->defs[i].keysz, key, sz))
+			return(&ep->defs[i]);
 
-	ep->cur = ep->rew;
+	return(NULL);
 }
 
+/*
+ * Get the next token from the input stream using the given quote
+ * character.
+ * Optionally make any replacements.
+ */
 static const char *
 eqn_next(struct eqn_node *ep, char quote, size_t *sz, int repl)
 {
@@ -822,48 +450,157 @@ again:
 	return(start);
 }
 
-static int
-eqn_do_ign1(struct eqn_node *ep)
+/*
+ * Get the next delimited token using the default current quote
+ * character.
+ */
+static const char *
+eqn_nexttok(struct eqn_node *ep, size_t *sz)
 {
 
-	if (NULL == eqn_nextrawtok(ep, NULL))
-		EQN_MSG(MANDOCERR_EQNEOF, ep);
-	else
-		return(1);
+	return(eqn_next(ep, '"', sz, 1));
+}
+
+/*
+ * Get next token without replacement.
+ */
+static const char *
+eqn_nextrawtok(struct eqn_node *ep, size_t *sz)
+{
 
-	return(0);
+	return(eqn_next(ep, '"', sz, 0));
 }
 
-static int
-eqn_do_ign2(struct eqn_node *ep)
+/*
+ * Parse a token from the stream of text.
+ * A token consists of one of the recognised eqn(7) strings.
+ * Strings are separated by delimiting marks.
+ * This returns EQN_TOK_EOF when there are no more tokens.
+ * If the token is an unrecognised string literal, then it returns
+ * EQN_TOK__MAX and sets the "p" pointer to an allocated, nil-terminated
+ * string.
+ * This must be later freed with free(3).
+ */
+static enum eqn_tok
+eqn_tok_parse(struct eqn_node *ep, char **p)
 {
+	const char	*start;
+	size_t		 i, sz;
 
-	if (NULL == eqn_nextrawtok(ep, NULL))
-		EQN_MSG(MANDOCERR_EQNEOF, ep);
-	else if (NULL == eqn_nextrawtok(ep, NULL))
-		EQN_MSG(MANDOCERR_EQNEOF, ep);
-	else
-		return(1);
+	if (NULL != p)
+		*p = NULL;
+
+	if (NULL == (start = eqn_nexttok(ep, &sz)))
+		return(EQN_TOK_EOF);
+
+	for (i = 0; i < EQN_TOK__MAX; i++) {
+		if (NULL == eqn_toks[i])
+			continue;
+		if (STRNEQ(start, sz, eqn_toks[i], strlen(eqn_toks[i])))
+			break;
+	}
+
+	if (i == EQN_TOK__MAX && NULL != p)
+		*p = mandoc_strndup(start, sz);
+
+	return(i);
+}
+
+static void
+eqn_box_free(struct eqn_box *bp)
+{
 
-	return(0);
+	if (bp->first)
+		eqn_box_free(bp->first);
+	if (bp->next)
+		eqn_box_free(bp->next);
+
+	free(bp->text);
+	free(bp->left);
+	free(bp->right);
+	free(bp->top);
+	free(bp->bottom);
+	free(bp);
 }
 
+/*
+ * Allocate a box as the last child of the parent node.
+ */
+static struct eqn_box *
+eqn_box_alloc(struct eqn_node *ep, struct eqn_box *parent)
+{
+	struct eqn_box	*bp;
+
+	bp = mandoc_calloc(1, sizeof(struct eqn_box));
+	bp->parent = parent;
+	bp->parent->args++;
+	bp->expectargs = UINT_MAX;
+	bp->size = ep->gsize;
+
+	assert(NULL != parent);
+
+	if (NULL != parent->first) {
+		assert(NULL != parent->last);
+		parent->last->next = bp;
+		bp->prev = parent->last;
+	} else
+		parent->first = bp;
+
+	parent->last = bp;
+	return(bp);
+}
+
+/*
+ * Reparent the current last node (of the current parent) under a new
+ * EQN_SUBEXPR as the first element.
+ * Then return the new parent.
+ * The new EQN_SUBEXPR will have a two-child limit.
+ */
+static struct eqn_box *
+eqn_box_makebinary(struct eqn_node *ep, 
+	enum eqn_post pos, struct eqn_box *parent)
+{
+	struct eqn_box	*b, *newb;
+
+	assert(NULL != parent->last);
+	b = parent->last;
+	if (parent->last == parent->first)
+		parent->first = NULL;
+	parent->args--;
+	parent->last = b->prev;
+	b->prev = NULL;
+	newb = eqn_box_alloc(ep, parent);
+	newb->pos = pos;
+	newb->type = EQN_SUBEXPR;
+	newb->expectargs = 2;
+	newb->args = 1;
+	newb->first = newb->last = b;
+	newb->first->next = NULL;
+	b->parent = newb;
+	return(newb);
+}
+
+/*
+ * Undefine a previously-defined string.
+ */
 static int
-eqn_do_tdefine(struct eqn_node *ep)
+eqn_undef(struct eqn_node *ep)
 {
+	const char	*start;
+	struct eqn_def	*def;
+	size_t		 sz;
 
-	if (NULL == eqn_nextrawtok(ep, NULL))
-		EQN_MSG(MANDOCERR_EQNEOF, ep);
-	else if (NULL == eqn_next(ep, ep->data[(int)ep->cur], NULL, 0))
+	if (NULL == (start = eqn_nextrawtok(ep, &sz))) {
 		EQN_MSG(MANDOCERR_EQNEOF, ep);
-	else
-		return(1);
+		return(0);
+	} else if (NULL != (def = eqn_def_find(ep, start, sz)))
+		def->keysz = 0;
 
-	return(0);
+	return(1);
 }
 
 static int
-eqn_do_define(struct eqn_node *ep)
+eqn_def(struct eqn_node *ep)
 {
 	const char	*start;
 	size_t		 sz;
@@ -879,7 +616,6 @@ eqn_do_define(struct eqn_node *ep)
 	 * Search for a key that already exists.
 	 * Create a new key if none is found.
 	 */
-
 	if (NULL == (def = eqn_def_find(ep, start, sz))) {
 		/* Find holes in string array. */
 		for (i = 0; i < (int)ep->defsz; i++)
@@ -906,7 +642,7 @@ eqn_do_define(struct eqn_node *ep)
 
 	if (NULL == start) {
 		EQN_MSG(MANDOCERR_EQNEOF, ep);
-		return(0);
+		return(-1);
 	}
 
 	def->valsz = sz;
@@ -916,56 +652,449 @@ eqn_do_define(struct eqn_node *ep)
 	return(1);
 }
 
+/*
+ * Recursively parse an eqn(7) expression.
+ */
 static int
-eqn_do_gfont(struct eqn_node *ep)
-{
-
-	if (NULL == eqn_nextrawtok(ep, NULL)) {
-		EQN_MSG(MANDOCERR_EQNEOF, ep);
-		return(0);
-	}
-	return(1);
-}
-
-static int
-eqn_do_gsize(struct eqn_node *ep)
+eqn_parse(struct eqn_node *ep, struct eqn_box *parent)
 {
+	char		*p;
+	enum eqn_tok	 tok;
+	enum eqn_post	 pos;
+	struct eqn_box	*cur;
+	int		 rc, size;
+	size_t		 i, sz;
+	char		 sym[64];
 	const char	*start;
-	size_t		 sz;
 
-	if (NULL == (start = eqn_nextrawtok(ep, &sz))) {
-		EQN_MSG(MANDOCERR_EQNEOF, ep);
+	assert(NULL != parent);
+again:
+	
+	switch ((tok = eqn_tok_parse(ep, &p))) {
+	case (EQN_TOK_UNDEF):
+		if ((rc = eqn_undef(ep)) <= 0)
+			return(rc);
+		break;
+	case (EQN_TOK_NDEFINE):
+	case (EQN_TOK_DEFINE):
+		if ((rc = eqn_def(ep)) <= 0)
+			return(rc);
+		break;
+	case (EQN_TOK_TDEFINE):
+		if (NULL == eqn_nextrawtok(ep, NULL))
+			EQN_MSG(MANDOCERR_EQNEOF, ep);
+		else if (NULL == eqn_next(ep, 
+				ep->data[(int)ep->cur], NULL, 0))
+			EQN_MSG(MANDOCERR_EQNEOF, ep);
+		break;
+	case (EQN_TOK_GFONT):
+		if (NULL == eqn_nextrawtok(ep, NULL)) {
+			EQN_MSG(MANDOCERR_EQNSYNT, ep);
+			return(-1);
+		}
+		break;
+	case (EQN_TOK_MARK):
+	case (EQN_TOK_LINEUP):
+		/* Ignore these. */
+		break;
+	case (EQN_TOK_DYAD):
+	case (EQN_TOK_VEC):
+	case (EQN_TOK_UNDER):
+	case (EQN_TOK_BAR):
+	case (EQN_TOK_TILDE):
+	case (EQN_TOK_HAT):
+	case (EQN_TOK_DOT):
+	case (EQN_TOK_DOTDOT):
+		if (NULL == parent->last) {
+			EQN_MSG(MANDOCERR_EQNSYNT, ep);
+			return(-1);
+		}
+		parent = eqn_box_makebinary
+			(ep, EQNPOS_NONE, parent);
+		parent->type = EQN_LISTONE;
+		parent->expectargs = 1;
+		switch (tok) {
+		case (EQN_TOK_DOTDOT):
+			strlcpy(sym, "\\[ad]", sizeof(sym));
+			break;
+		case (EQN_TOK_VEC):
+			strlcpy(sym, "\\[->]", sizeof(sym));
+			break;
+		case (EQN_TOK_DYAD):
+			strlcpy(sym, "\\[<>]", sizeof(sym));
+			break;
+		case (EQN_TOK_TILDE):
+			strlcpy(sym, "\\[a~]", sizeof(sym));
+			break;
+		case (EQN_TOK_UNDER):
+			strlcpy(sym, "\\[ul]", sizeof(sym));
+			break;
+		case (EQN_TOK_BAR):
+			strlcpy(sym, "\\[rl]", sizeof(sym));
+			break;
+		case (EQN_TOK_DOT):
+			strlcpy(sym, "\\[a.]", sizeof(sym));
+			break;
+		case (EQN_TOK_HAT):
+			strlcpy(sym, "\\[ha]", sizeof(sym));
+			break;
+		default:
+			abort();
+		}
+
+		switch (tok) {
+		case (EQN_TOK_DOTDOT):
+		case (EQN_TOK_VEC):
+		case (EQN_TOK_DYAD):
+		case (EQN_TOK_TILDE):
+		case (EQN_TOK_BAR):
+		case (EQN_TOK_DOT):
+		case (EQN_TOK_HAT):
+			parent->top = mandoc_strdup(sym);
+			break;
+		case (EQN_TOK_UNDER):
+			parent->bottom = mandoc_strdup(sym);
+			break;
+		default:
+			abort();
+		}
+		parent = parent->parent;
+		break;
+	case (EQN_TOK_FWD):
+	case (EQN_TOK_BACK):
+	case (EQN_TOK_DOWN):
+	case (EQN_TOK_UP):
+		tok = eqn_tok_parse(ep, NULL); 
+		if (EQN_TOK__MAX != tok) {
+			EQN_MSG(MANDOCERR_EQNSYNT, ep);
+			return(-1);
+		}
+		break;
+	case (EQN_TOK_FAT):
+	case (EQN_TOK_ROMAN):
+	case (EQN_TOK_ITALIC):
+	case (EQN_TOK_BOLD):
+		while (parent->args == parent->expectargs)
+			if (NULL == (parent = parent->parent)) {
+				EQN_MSG(MANDOCERR_EQNSYNT, ep);
+				return(-1);
+			}
+		/*
+		 * These values apply to the next word or sequence of
+		 * words; thus, we mark that we'll have a child with
+		 * exactly one of those.
+		 */
+		parent = eqn_box_alloc(ep, parent);
+		parent->type = EQN_LISTONE;
+		parent->expectargs = 1;
+		switch (tok) {
+		case (EQN_TOK_FAT):
+			parent->font = EQNFONT_FAT;
+			break;
+		case (EQN_TOK_ROMAN):
+			parent->font = EQNFONT_ROMAN;
+			break;
+		case (EQN_TOK_ITALIC):
+			parent->font = EQNFONT_ITALIC;
+			break;
+		case (EQN_TOK_BOLD):
+			parent->font = EQNFONT_BOLD;
+			break;
+		default:
+			abort();
+		}
+		break;
+	case (EQN_TOK_SIZE):
+	case (EQN_TOK_GSIZE):
+		/* Accept two values: integral size and a single. */
+		if (NULL == (start = eqn_nexttok(ep, &sz))) {
+			EQN_MSG(MANDOCERR_EQNSYNT, ep);
+			return(-1);
+		}
+		size = mandoc_strntoi(start, sz, 10);
+		if (-1 == size) {
+			EQN_MSG(MANDOCERR_EQNSYNT, ep);
+			return(-1);
+		}
+		if (EQN_TOK_GSIZE == tok) {
+			ep->gsize = size;
+			break;
+		}
+		parent = eqn_box_alloc(ep, parent);
+		parent->type = EQN_LISTONE;
+		parent->expectargs = 1;
+		parent->size = size;
+		break;
+	case (EQN_TOK_FROM):
+	case (EQN_TOK_TO):
+	case (EQN_TOK_SUB):
+	case (EQN_TOK_SUP):
+		/*
+		 * We have a left-right-associative expression.
+		 * Repivot under a positional node, open a child scope
+		 * and keep on reading.
+		 */
+		if (NULL == parent->last) {
+			EQN_MSG(MANDOCERR_EQNSYNT, ep);
+			return(-1);
+		}
+		/* Handle the "subsup" and "fromto" positions. */
+		if (EQN_TOK_SUP == tok && parent->pos == EQNPOS_SUB) {
+			parent->expectargs = 3;
+			parent->pos = EQNPOS_SUBSUP;
+			break;
+		}
+		if (EQN_TOK_TO == tok && parent->pos == EQNPOS_FROM) {
+			parent->expectargs = 3;
+			parent->pos = EQNPOS_FROMTO;
+			break;
+		}
+		switch (tok) {
+		case (EQN_TOK_FROM):
+			pos = EQNPOS_FROM;
+			break;
+		case (EQN_TOK_TO):
+			pos = EQNPOS_TO;
+			break;
+		case (EQN_TOK_SUP):
+			pos = EQNPOS_SUP;
+			break;
+		case (EQN_TOK_SUB):
+			pos = EQNPOS_SUB;
+			break;
+		default:
+			abort();
+		}
+		parent = eqn_box_makebinary(ep, pos, parent);
+		break;
+	case (EQN_TOK_SQRT):
+		while (parent->args == parent->expectargs)
+			if (NULL == (parent = parent->parent)) {
+				EQN_MSG(MANDOCERR_EQNSYNT, ep);
+				return(-1);
+			}
+		/* 
+		 * Accept a left-right-associative set of arguments just
+		 * like sub and sup and friends but without rebalancing
+		 * under a pivot.
+		 */
+		parent = eqn_box_alloc(ep, parent);
+		parent->type = EQN_SUBEXPR;
+		parent->pos = EQNPOS_SQRT;
+		parent->expectargs = 1;
+		break;
+	case (EQN_TOK_OVER):
+		/*
+		 * We have a right-left-associative fraction.
+		 * Close out anything that's currently open, then
+		 * rebalance and continue reading.
+		 */
+		if (NULL == parent->last) {
+			EQN_MSG(MANDOCERR_EQNSYNT, ep);
+			return(-1);
+		}
+		while (EQN_SUBEXPR == parent->type)
+			if (NULL == (parent = parent->parent)) {
+				EQN_MSG(MANDOCERR_EQNSYNT, ep);
+				return(-1);
+			}
+		parent = eqn_box_makebinary(ep, EQNPOS_OVER, parent);
+		break;
+	case (EQN_TOK_RIGHT):
+	case (EQN_TOK_BRACE_CLOSE):
+		/*
+		 * Close out the existing brace.
+		 * FIXME: this is a shitty sentinel: we should really
+		 * have a native EQN_BRACE type or whatnot.
+		 */
+		while (parent->type != EQN_LIST) 
+			if (NULL == (parent = parent->parent)) {
+				EQN_MSG(MANDOCERR_EQNSYNT, ep);
+				return(-1);
+			}
+		if (EQN_TOK_RIGHT == tok) {
+			if (NULL == parent->left) {
+				EQN_MSG(MANDOCERR_EQNSYNT, ep);
+				return(-1);
+			}
+			if (NULL == (start = eqn_nexttok(ep, &sz))) {
+				EQN_MSG(MANDOCERR_EQNSYNT, ep);
+				return(-1);
+			}
+			/* Handling depends on right/left. */
+			if (STRNEQ(start, sz, "ceiling", 7)) {
+				strlcpy(sym, "\\[rc]", sizeof(sym));
+				parent->right = mandoc_strdup(sym);
+			} else if (STRNEQ(start, sz, "floor", 5)) {
+				strlcpy(sym, "\\[rf]", sizeof(sym));
+				parent->right = mandoc_strdup(sym);
+			} else 
+				parent->right = mandoc_strndup(start, sz);
+		}
+		if (NULL == (parent = parent->parent)) {
+			EQN_MSG(MANDOCERR_EQNSYNT, ep);
+			return(-1);
+		}
+		if (EQN_TOK_BRACE_CLOSE == tok && parent && 
+			(parent->type == EQN_PILE ||
+			 parent->type == EQN_MATRIX))
+			parent = parent->parent;
+		/* Close out any "singleton" lists. */
+		while (parent->type == EQN_LISTONE && 
+			parent->args == parent->expectargs)
+			if (NULL == (parent = parent->parent)) {
+				EQN_MSG(MANDOCERR_EQNSYNT, ep);
+				return(-1);
+			}
+		break;
+	case (EQN_TOK_BRACE_OPEN):
+	case (EQN_TOK_LEFT):
+		/*
+		 * If we already have something in the stack and we're
+		 * in an expression, then rewind til we're not any more
+		 * (just like with the text node).
+		 */
+		while (parent->args == parent->expectargs)
+			if (NULL == (parent = parent->parent)) {
+				EQN_MSG(MANDOCERR_EQNSYNT, ep);
+				return(-1);
+			}
+		parent = eqn_box_alloc(ep, parent);
+		parent->type = EQN_LIST;
+		if (EQN_TOK_LEFT == tok) {
+			if (NULL == (start = eqn_nexttok(ep, &sz))) {
+				EQN_MSG(MANDOCERR_EQNSYNT, ep);
+				return(-1);
+			}
+			/* Handling depends on right/left. */
+			if (STRNEQ(start, sz, "ceiling", 7)) {
+				strlcpy(sym, "\\[lc]", sizeof(sym));
+				parent->left = mandoc_strdup(sym);
+			} else if (STRNEQ(start, sz, "floor", 5)) {
+				strlcpy(sym, "\\[lf]", sizeof(sym));
+				parent->left = mandoc_strdup(sym);
+			} else 
+				parent->left = mandoc_strndup(start, sz);
+		}
+		break;
+	case (EQN_TOK_PILE):
+	case (EQN_TOK_LPILE):
+	case (EQN_TOK_RPILE):
+	case (EQN_TOK_CPILE):
+	case (EQN_TOK_CCOL):
+	case (EQN_TOK_LCOL):
+	case (EQN_TOK_RCOL):
+		while (parent->args == parent->expectargs)
+			if (NULL == (parent = parent->parent)) {
+				EQN_MSG(MANDOCERR_EQNSYNT, ep);
+				return(-1);
+			}
+		if (EQN_TOK_BRACE_OPEN != eqn_tok_parse(ep, NULL)) {
+			EQN_MSG(MANDOCERR_EQNSYNT, ep);
+			return(-1);
+		}
+		parent = eqn_box_alloc(ep, parent);
+		parent->type = EQN_PILE;
+		parent = eqn_box_alloc(ep, parent);
+		parent->type = EQN_LIST;
+		break;
+	case (EQN_TOK_ABOVE):
+		while (parent->type != EQN_PILE) 
+			if (NULL == (parent = parent->parent)) {
+				EQN_MSG(MANDOCERR_EQNSYNT, ep);
+				return(-1);
+			}
+		parent = eqn_box_alloc(ep, parent);
+		parent->type = EQN_LIST;
+		break;
+	case (EQN_TOK_MATRIX):
+		while (parent->args == parent->expectargs)
+			if (NULL == (parent = parent->parent)) {
+				EQN_MSG(MANDOCERR_EQNSYNT, ep);
+				return(-1);
+			}
+		if (EQN_TOK_BRACE_OPEN != eqn_tok_parse(ep, NULL)) {
+			EQN_MSG(MANDOCERR_EQNSYNT, ep);
+			return(-1);
+		}
+		parent = eqn_box_alloc(ep, parent);
+		parent->type = EQN_MATRIX;
+		parent = eqn_box_alloc(ep, parent);
+		parent->type = EQN_LIST;
+		break;
+	case (EQN_TOK_EOF):
+		/*
+		 * End of file! 
+		 * TODO: make sure we're not in an open subexpression.
+		 */
 		return(0);
+	default:
+		assert(tok == EQN_TOK__MAX);
+		assert(NULL != p);
+		/*
+		 * If we already have something in the stack and we're
+		 * in an expression, then rewind til we're not any more.
+		 */
+		while (parent->args == parent->expectargs)
+			if (NULL == (parent = parent->parent)) {
+				EQN_MSG(MANDOCERR_EQNSYNT, ep);
+				free(p);
+				return(-1);
+			}
+		cur = eqn_box_alloc(ep, parent);
+		cur->type = EQN_TEXT;
+		for (i = 0; i < EQNSYM__MAX; i++)
+			if (0 == strcmp(eqnsyms[i].str, p)) {
+				(void)snprintf(sym, sizeof(sym), 
+					"\\[%s]", eqnsyms[i].sym);
+				cur->text = mandoc_strdup(sym);
+				free(p);
+				break;
+			}
+
+		if (i == EQNSYM__MAX)
+			cur->text = p;
+		/*
+		 * Post-process list status.
+		 */
+		while (parent->type == EQN_LISTONE && 
+			parent->args == parent->expectargs)
+			if (NULL == (parent = parent->parent)) {
+				EQN_MSG(MANDOCERR_EQNSYNT, ep);
+				return(-1);
+			}
+		break;
 	}
-	ep->gsize = mandoc_strntoi(start, sz, 10);
-	return(1);
+	goto again;
 }
 
-static int
-eqn_do_undef(struct eqn_node *ep)
+enum rofferr
+eqn_end(struct eqn_node **epp) 
 {
-	const char	*start;
-	struct eqn_def	*def;
-	size_t		 sz;
+	struct eqn_node	*ep;
 
-	if (NULL == (start = eqn_nextrawtok(ep, &sz))) {
-		EQN_MSG(MANDOCERR_EQNEOF, ep);
-		return(0);
-	} else if (NULL != (def = eqn_def_find(ep, start, sz)))
-		def->keysz = 0;
+	ep = *epp;
+	*epp = NULL;
 
-	return(1);
+	ep->eqn.root = mandoc_calloc(1, sizeof(struct eqn_box));
+	ep->eqn.root->expectargs = UINT_MAX;
+	return(0 == eqn_parse(ep, ep->eqn.root) ? ROFF_EQN : ROFF_IGN);
 }
 
-static struct eqn_def *
-eqn_def_find(struct eqn_node *ep, const char *key, size_t sz)
+void
+eqn_free(struct eqn_node *p)
 {
 	int		 i;
 
-	for (i = 0; i < (int)ep->defsz; i++)
-		if (ep->defs[i].keysz && STRNEQ(ep->defs[i].key,
-		    ep->defs[i].keysz, key, sz))
-			return(&ep->defs[i]);
+	eqn_box_free(p->eqn.root);
 
-	return(NULL);
+	for (i = 0; i < (int)p->defsz; i++) {
+		free(p->defs[i].key);
+		free(p->defs[i].val);
+	}
+
+	free(p->eqn.name);
+	free(p->data);
+	free(p->defs);
+	free(p);
 }