/** \brief Given \c a, an expression that is the denotation of an expression, if \c a is a variable,
then use the actions in the transitions \c ts to expand \c a. The idea is to produce a head symbol
we can use to decide whether the notation should be considered during pretty printing.
\see get_head_index
*/
static expr expand_pp_pattern(unsigned num, transition const * ts, expr const & a) {
lean_assert(is_simple(num, ts));
if (!is_var(a))
return a;
return replace(a, [&](expr const & e) {
if (is_var(e)) {
unsigned vidx = var_idx(e);
unsigned i = num;
unsigned offset = 0;
while (i > 0) {
--i;
action const & act = ts[i].get_action();
switch (act.kind()) {
case action_kind::Binder: case action_kind::Binders: case action_kind::Skip:
break;
case action_kind::Ext: case action_kind::LuaExt:
lean_unreachable();
case action_kind::Expr:
if (vidx == 0) return none_expr();
offset++;
vidx--;
break;
case action_kind::Exprs:
if (vidx == 0)
return some_expr(lift_free_vars(act.get_rec(), offset));
offset++;
vidx--;
break;
case action_kind::ScopedExpr:
if (vidx == 0)
return some_expr(lift_free_vars(act.get_rec(), offset));
offset++;
vidx--;
break;
}
}
return none_expr();
} else {
return none_expr();
}
});
}
static expr lift(expr const & e) { return lift_free_vars(e, 1); }
