README.md

About

Risa is an embeddable and modular scripting language.

This implementation is extremely early, work-in-progress and, therefore, not yet ready for an alpha release. Many parts of the code are temporary, and WILL be changed.

Extended BNF (EBNF) notation

This is the EBNF notation for Risa's grammar.

script ::= ( space declaration space )* EOF ;

declaration ::= fnDecl
              | varDecl
              | stmt ;

fnDecl  ::= "function" space fn ;
varDecl ::= "var" space IDENTIFIER ( space "=" expr)? ";" ;

fn     ::= IDENTIFIER space "(" space params? space ")" ( block | "=>" expr );
params ::= IDENTIFIER ( "," space IDENTIFIER )* ;

stmt ::= exprStmt
       | ifStmt
       | whileStmt
       | forStmt
       | returnStmt
       | continueStmt
       | breakStmt
       | block ;

exprStmt     ::= expr ";" space ;
ifStmt       ::= "if" space "(" expr ")" space stmt space ( space "else" space stmt space )? ;
whileStmt    ::= "while" space "(" expr ")" space stmt ;
forStmt      ::= "for" "(" ( varDec | exprStmt | ";" ) expr? ";" expr? ")" space stmt ;
returnStmt   ::= space "return" expr? ";" ;
continueStmt ::= space "continue" INTEGER? ";" ;
breakStmt    ::= space "break" INTEGER? ";" ;
block        ::= space "{" declaration* "}" ;

expr ::= space comma space ;

comma ::= assignment space "," space assignment ;

assignment ::= ( call space "." space )? IDENTIFIER space "=" space assignment
             | ternary ;

ternary ::= or space "?" expr ":" expr ;

or  ::= and ( "||" and)* ;
and ::= bitwiseOr ( "&&" bitwiseOr )* ;

bitwiseOr  ::= bitwiseXor ( "|" bitwiseXor )* ;
bitwiseXor ::= bitwiseAnd ( "^" bitwiseAnd )* ;
bitwiseAnd ::= equality ( "&" equality )* ;

equality       ::= comparison ( ( "==" | "!=" ) comparison )* ;
comparison     ::= shift ( ( "<" | "<=" | ">" | ">=" ) shift )* ;
shift          ::= addition ( ( "<<" | ">>" ) addition )* ;
addition       ::= multiplication ( ( "+" | "-" ) multiplication )* ;
multiplication ::= unary ( ( "*" | "/" | "%" ) unary )* ;

unary ::= space ( ( "!" | "-" | "~" ) unary | call ) space ;
call  ::= primary ( "(" args? ")" | "[" expr "]" | "." IDENTIFIER )* ;
args  ::= expr ( "," expr )* ;

primary ::= "null"
          | "true"
          | "false"
          | NUMBER
          | STRING
          | IDENTIFIER
          | "(" expr ")" 
          | lambda
          | array ;

lambda ::= "(" args? ")" space "=>" ( expr | block ) ;

array ::= "[" args? "]" ;

space ::= ""
        | " "
        | "\t"
        | "\r"
        | "\n"
        | comment ;

comment ::= "//" ( COMMENTCHAR )*
          | "/*" ( ANYCHAR )* "*/" ;

COMMENTCHAR ::= [#x00-#x09#x0B-#xFF] ;
ANYCHAR     ::= [#x00-#xFF] ;

NUMBER ::= BYTE
         | INTEGER
         | FLOAT ;

STRING     ::= "\"" STRCHAR "\"" ;
IDENTIFIER ::= ALPHA ( ALPHA | DIGIT )* ;

BYTE    ::= DIGIT+ "b" ;
INTEGER ::= DIGIT+ ;
FLOAT   ::= DIGIT+ "." DIGIT+ [ "f" ]
          | DIGIT+ "f" ;

STRCHAR ::= [#x00-#x09#x0B-#x21#x23-#xFF] | "\\\"" ;

ALPHA ::= [a-zA-Z] | "_" ;
DIGIT ::= [0-9] ;

License

This project was created by The Exom Developers.

The Risa project is licensed under the MIT license.

References

• Crafting Interpreters
• The Implementation of Lua 5.0