+enum eqn_boxt {
+ EQN_ROOT, /* root of parse tree */
+ EQN_TEXT, /* text (number, variable, whatever) */
+ EQN_SUBEXPR, /* nested `eqn' subexpression */
+ EQN_LIST, /* subexpressions list */
+ EQN_MATRIX /* matrix subexpression */
+};
+
+enum eqn_markt {
+ EQNMARK_NONE = 0,
+ EQNMARK_DOT,
+ EQNMARK_DOTDOT,
+ EQNMARK_HAT,
+ EQNMARK_TILDE,
+ EQNMARK_VEC,
+ EQNMARK_DYAD,
+ EQNMARK_BAR,
+ EQNMARK_UNDER,
+ EQNMARK__MAX
+};
+
+enum eqn_fontt {
+ EQNFONT_NONE = 0,
+ EQNFONT_ROMAN,
+ EQNFONT_BOLD,
+ EQNFONT_FAT,
+ EQNFONT_ITALIC,
+ EQNFONT__MAX
+};
+
+enum eqn_post {
+ EQNPOS_NONE = 0,
+ EQNPOS_OVER,
+ EQNPOS_SUP,
+ EQNPOS_SUB,
+ EQNPOS_TO,
+ EQNPOS_FROM,
+ EQNPOS__MAX
+};
+
+enum eqn_pilet {
+ EQNPILE_NONE = 0,
+ EQNPILE_PILE,
+ EQNPILE_CPILE,
+ EQNPILE_RPILE,
+ EQNPILE_LPILE,
+ EQNPILE_COL,
+ EQNPILE_CCOL,
+ EQNPILE_RCOL,
+ EQNPILE_LCOL,
+ EQNPILE__MAX
+};
+
+ /*
+ * A "box" is a parsed mathematical expression as defined by the eqn.7
+ * grammar.
+ */
+struct eqn_box {
+ int size; /* font size of expression */
+#define EQN_DEFSIZE INT_MIN
+ enum eqn_boxt type; /* type of node */
+ struct eqn_box *first; /* first child node */
+ struct eqn_box *last; /* last child node */
+ struct eqn_box *next; /* node sibling */
+ struct eqn_box *parent; /* node sibling */
+ char *text; /* text (or NULL) */
+ char *left;
+ char *right;
+ enum eqn_post pos; /* position of next box */
+ enum eqn_markt mark; /* a mark about the box */
+ enum eqn_fontt font; /* font of box */
+ enum eqn_pilet pile; /* equation piling */
+};
+
+/*
+ * An equation consists of a tree of expressions starting at a given
+ * line and position.
+ */