17.6 Solution for cleardivert

The cleardivert macro (see Cleardivert) cannot, as it stands, be called without arguments to clear all pending diversions. That is because using undivert with an empty string for an argument is different than using it with no arguments at all. Compare the earlier definition with one that takes the number of arguments into account:

define(`cleardivert',
  `pushdef(`_n', divnum)divert(`-1')undivert($@)divert(_n)popdef(`_n')')
⇒
divert(`1')one
divert
⇒
cleardivert
⇒
undivert
⇒one
⇒
define(`cleardivert',
  `pushdef(`_num', divnum)divert(`-1')ifelse(`$#', `0',
    `undivert`'', `undivert($@)')divert(_num)popdef(`_num')')
⇒
divert(`2')two
divert
⇒
cleardivert
⇒
undivert
⇒