I copy your code below, because it's so terse and marvellous and I don't want to deprive anyone who assumes otherwise and doesn't click on your link: : >BR

I copy your code below, because it's so terse and marvellous and I don't want to deprive anyone who assumes otherwise and doesn't click on your link: : >BRACES 1 CELLS BRACES +! BRACES @ ! ; : BRACES> BRACES @ @ -1 CELLS BRACES +! ; : { DEPTH >BRACES ; : } DEPTH BRACES> 1+ <> ABORT"unbalanced" ; And the example "backwards lisp" expressions you give as test cases: { 1 2 + } . { 5 { 1 2 + } * }