17.1 Solution for exch

The exch macro (see section Arguments to macros) as presented requires clients to double quote their arguments. A nicer definition, which lets clients follow the rule of thumb of one level of quoting per level of parentheses, involves adding quotes in the definition of exch, as follows:

define(`exch', ``$2', `$1'')
⇒
define(exch(`expansion text', `macro'))
⇒
macro
⇒expansion text