-commands.rule = "\\blackrule[height=0.5pt,depth=0pt,width=.40\\textwidth]"
--- Pretty printer to use for the stuff before and after the line
-commands.before_pret = "lam"
-commands.after_pret = "lam"
+commands.rule = "\\HLine[width=.40 * \\the\\textwidth]"
+-- Typing environment to use for the stuff before and after the line. Will be
+-- prefixed with \start and \stop automatically.
+commands.beforeenv = "unboxedlambda"
+commands.afterenv = "unboxedlambda"