3 ms·

While true, this is not officially supported as part of the RnRS standard I believe. They set these characters aside as reserved for future use.

• mikegerwitz 9y ago
  Yes, you're correct. R7RS at least explicitly reserves brackets and braces, and only acknowledges parenthesis in its syntax.
• lispm 9y ago
  I think this depends on which RnRS you look at.
  • eatonphil 9y ago
    Do some of the older ones just completely omit reserving them?
    • lispm 9y ago
      R6RS: pairs and lists, enclosed by ( ) or [ ] (see section 4.3.2)
      • eatonphil 9y ago
        Ah the problem child. :) I've mostly only paid attention to R5RS and R7RS.