Many Scheme implementations support square brackets as alternative to parentheses, enabling a (supposedly) more readable syntax: ``` (let ([a 3]) ...) (define-checked (a [b string?] [c number?]) ...) ``` And others. Any reason Kawa does not support that? R7RS [says that these are reserved](https://r7rs.aartaka.me/#2.3): > Left and right square and curly brackets (braces) are reserved for possible future extensions to the language. But the common practice goes the other way.