Formal syntax for a minimal Scheme

scheme.bnf

/* Play with it: https://bnfplayground.pauliankline.com/ */

<sexpr> ::= <atom> | <list> | <quote> | <unquote>

<atom> ::= <any>+
<list> ::= "(" " "* (<sexpr> " "+)* <sexpr>? ")" 
<quote> ::= "'" <sexpr>
<unquote> ::= "," <sexpr>

<any> ::= <alpha> | <special>
<alpha> ::= [0-9] | [a-z] | [A-Z]
<special> ::=
	"!" | "$" | "%" | "&" | "*" | "+" | "-" | "." | "/" |
	":" | "<" | "=" | ">" | "?" | "@" | "^" | "_" | "~"