SCM find_expression_fonts (SCM expr);
void register_stencil_head (SCM symbol);
bool is_stencil_head (SCM symbol);
SCM all_stencil_heads ();
SCM find_expression_fonts (SCM expr);
void register_stencil_head (SCM symbol);
bool is_stencil_head (SCM symbol);
SCM all_stencil_heads ();