[mikegerwitz]

Some lisps use parenthesis and brackets interchangeably. Some people prefer to strategically alternate them, but you're free to use them exclusively.

Guile Scheme, for example:

  scheme@(guile-user)> [list 1 2 3] 
  $1 = (1 2 3)
  scheme@(guile-user)> (list 1 2 3) 
  $2 = (1 2 3)
  scheme@(guile-user)> [car '[1 2 3]]
  $3 = 1

[eatonphil]

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]

Yes, you're correct. R7RS at least explicitly reserves brackets and braces, and only acknowledges parenthesis in its syntax.

[lispm]

I think this depends on which RnRS you look at.

[eatonphil]

Do some of the older ones just completely omit reserving them?

[lispm]

R6RS: pairs and lists, enclosed by ( ) or [ ] (see section 4.3.2)

[eatonphil]

Ah the problem child. :) I've mostly only paid attention to R5RS and R7RS.