GBNF language preview

1. A JSON-ish grammar

rule definitions, quoted terminals, and character classes

horizon-dark

# a simple JSON-ish grammar
root ::= object
object ::= "{" pair ("," pair)* "}"
pair ::= string ":" value
value ::= string | number | object
string ::= "\"" [^"]* "\""
number ::= [0-9]+ ("." [0-9]+)?

atom-one-dark

# a simple JSON-ish grammar
root ::= object
object ::= "{" pair ("," pair)* "}"
pair ::= string ":" value
value ::= string | number | object
string ::= "\"" [^"]* "\""
number ::= [0-9]+ ("." [0-9]+)?

github-dark

# a simple JSON-ish grammar
root ::= object
object ::= "{" pair ("," pair)* "}"
pair ::= string ":" value
value ::= string | number | object
string ::= "\"" [^"]* "\""
number ::= [0-9]+ ("." [0-9]+)?

dracula

# a simple JSON-ish grammar
root ::= object
object ::= "{" pair ("," pair)* "}"
pair ::= string ":" value
value ::= string | number | object
string ::= "\"" [^"]* "\""
number ::= [0-9]+ ("." [0-9]+)?

nord

# a simple JSON-ish grammar
root ::= object
object ::= "{" pair ("," pair)* "}"
pair ::= string ":" value
value ::= string | number | object
string ::= "\"" [^"]* "\""
number ::= [0-9]+ ("." [0-9]+)?

github

# a simple JSON-ish grammar
root ::= object
object ::= "{" pair ("," pair)* "}"
pair ::= string ":" value
value ::= string | number | object
string ::= "\"" [^"]* "\""
number ::= [0-9]+ ("." [0-9]+)?

2. Quantifiers

optional, one-or-more, and repetition ranges

horizon-dark

root ::= greeting name? "!"+
greeting ::= "hi" | "hello"
name ::= [a-zA-Z]{1,20}

atom-one-dark

root ::= greeting name? "!"+
greeting ::= "hi" | "hello"
name ::= [a-zA-Z]{1,20}

github-dark

root ::= greeting name? "!"+
greeting ::= "hi" | "hello"
name ::= [a-zA-Z]{1,20}

dracula

root ::= greeting name? "!"+
greeting ::= "hi" | "hello"
name ::= [a-zA-Z]{1,20}

nord

root ::= greeting name? "!"+
greeting ::= "hi" | "hello"
name ::= [a-zA-Z]{1,20}

github

root ::= greeting name? "!"+
greeting ::= "hi" | "hello"
name ::= [a-zA-Z]{1,20}

3. Grouping and alternation

grouped alternatives inside a rule

horizon-dark

expr ::= term (("+" | "-") term)*
term ::= factor (("*" | "/") factor)*
factor ::= [0-9]+ | "(" expr ")"

atom-one-dark

expr ::= term (("+" | "-") term)*
term ::= factor (("*" | "/") factor)*
factor ::= [0-9]+ | "(" expr ")"

github-dark

expr ::= term (("+" | "-") term)*
term ::= factor (("*" | "/") factor)*
factor ::= [0-9]+ | "(" expr ")"

dracula

expr ::= term (("+" | "-") term)*
term ::= factor (("*" | "/") factor)*
factor ::= [0-9]+ | "(" expr ")"

nord

expr ::= term (("+" | "-") term)*
term ::= factor (("*" | "/") factor)*
factor ::= [0-9]+ | "(" expr ")"

github

expr ::= term (("+" | "-") term)*
term ::= factor (("*" | "/") factor)*
factor ::= [0-9]+ | "(" expr ")"