chaiscript.ebnf

/*
 * ChaiScript Grammar — EBNF for Railroad Diagram Generation
 *
 * View as navigable railroad diagrams at:
 *    https://www.bottlecaps.de/rr/ui  (IPv6)
 *    https://rr.red-dove.com/ui       (IPv4)
 *
 * Copy and paste this file into the 'Edit Grammar' tab, then
 * click 'View Diagram'.
 *
 * This grammar uses the notation accepted by
 * https://github.com/GuntherRademacher/rr :
 *   - "::=" as rule separator
 *   - no semicolon at end of rule
 *   - "?" "+" "*" for repetition
 *   - C comments
 */

/* ---- Top-level ---- */

statements           ::= ( def | try | if | while | class | enum
                           | for | switch | return | break | continue
                           | equation | block | eol )+

/* ---- Functions ---- */

def                  ::= "def" id ( "::" id )? "(" decl_arg_list ")" eol*
                           ( ":" guard )? eol* block

lambda               ::= "fun" ( "[" id_arg_list "]" )? "(" decl_arg_list ")" eol* block

guard                ::= operator

/* ---- Exception handling ---- */

try                  ::= "try" eol* block catch* finally?
catch                ::= "catch" ( "(" arg ")" )? eol* block
finally              ::= "finally" eol* block

/* ---- Control flow ---- */

if                   ::= "if" "(" equation ( eol equation )? ")" eol* block
                           ( "else" ( if | eol* block ) )*

while                ::= "while" "(" operator ")" eol* block

for                  ::= "for" "(" ( for_guards | equation ":" equation ) ")" eol* block
for_guards           ::= equation eol equation eol equation

switch               ::= "switch" "(" operator ")" eol* "{" ( case | default )+ "}"
case                 ::= "case" "(" operator ")" eol* block
default              ::= "default" eol* block

/* ---- Classes ---- */

class                ::= "class" id ( ":" id )? eol* class_block
class_block          ::= "{" class_statements* "}"
class_statements     ::= def | var_decl | eol

/* ---- Enums ---- */

enum                 ::= "enum" ( "class" | "struct" ) id ( ":" underlying_type )?
                           "{" enum_entries? "}"

enum_entries         ::= enum_entry ( "," enum_entry )*

enum_entry           ::= id ( "=" integer )?

underlying_type      ::= id


/* ---- Blocks & flow keywords ---- */

block                ::= "{" statements* "}"
return               ::= "return" operator?
break                ::= "break"
continue             ::= "continue"

/* ---- Line termination ---- */

eol                  ::= "\n" | "\r\n" | ";"

/* ---- Equations & operators ---- */

equation             ::= operator ( ( "=" | ":=" | "+=" | "-=" | "*=" | "/="
                           | "%=" | "<<=" | ">>=" | "&=" | "^=" | "|=" )
                           equation )?

operator             ::= prefix
                       | value
                       | operator binary_operator operator
                       | operator "?" operator ":" operator

prefix               ::= ( "++" | "--" | "-" | "+" | "!" | "~" ) operator

binary_operator      ::= "||" | "&&"
                       | "|" | "^" | "&"
                       | "==" | "!="
                       | "<" | "<=" | ">" | ">="
                       | "<<" | ">>"
                       | "+" | "-"
                       | "*" | "/" | "%"

/* ---- Values & access ---- */

value                ::= var_decl | dot_fun_array | prefix

dot_fun_array        ::= ( lambda | num | quoted_string
                           | single_quoted_string | raw_string
                           | paren_expression | inline_container
                           | id )
                           ( fun_call | array_call | dot_access )*

fun_call             ::= "(" arg_list ")"
array_call           ::= "[" operator "]"
dot_access           ::= "." id

/* ---- Variable declarations ---- */

var_decl             ::= ( "auto" | "var" | "const" ) ( reference | id )
                       | "global" ( reference | id )
                       | "attr" id ( "::" id )?

reference            ::= "&" id

/* ---- Parenthesised & inline containers ---- */

paren_expression     ::= "(" operator ")"

inline_container     ::= "[" container_arg_list "]"
container_arg_list   ::= value_range
                       | map_pair ( "," map_pair )*
                       | operator ( "," operator )*

value_range          ::= operator ".." operator
map_pair             ::= operator ":" operator

/* ---- String literals ---- */

quoted_string        ::= '"' ( char | escape | interpolation )* '"'
single_quoted_string ::= "'" ( char | escape ) "'"
raw_string           ::= 'R"' delimiter? "(" char* ")" delimiter? '"'
delimiter            ::= [a-zA-Z0-9_]+
interpolation        ::= "${" equation "}"

/* ---- Escape sequences ---- */

escape               ::= "\" ( "'" | '"' | "?" | "\" | "a" | "b"
                           | "f" | "n" | "r" | "t" | "v" | "$"
                           | "0"
                           | "x" hex_digit+
                           | "u" hex_digit hex_digit hex_digit hex_digit
                           | "U" hex_digit hex_digit hex_digit hex_digit
                               hex_digit hex_digit hex_digit hex_digit
                           | octal_digit+ )

/* ---- Argument lists ---- */

id_arg_list          ::= id ( "," id )*
decl_arg_list        ::= ( arg ( "," arg )* )?
arg_list             ::= ( equation ( "," equation )* )?
arg                  ::= id id?

/* ---- Identifiers ---- */

id                   ::= ( [a-zA-Z_] [a-zA-Z0-9_]* )
                       | ( "`" [^`]+ "`" )
                       | "true" | "false"
                       | "Infinity" | "NaN"
                       | "_"
                       | "__LINE__" | "__FILE__" | "__FUNC__" | "__CLASS__"

/* ---- Numeric literals ---- */

num                  ::= hex | binary | float | integer

hex                  ::= "0" ( "x" | "X" ) [0-9a-fA-F]+ int_suffix*
binary               ::= "0" ( "b" | "B" ) [01]+ int_suffix*
float                ::= [0-9]+ "." [0-9]+ ( ( "e" | "E" ) ( "+" | "-" )? [0-9]+ )? float_suffix?
integer              ::= [0-9]+ int_suffix*

int_suffix           ::= "l" | "L" | "ll" | "LL" | "u" | "U"
float_suffix         ::= "l" | "L" | "f" | "F"

/* ---- Character classes ---- */

octal_digit          ::= [0-7]
hex_digit            ::= [0-9a-fA-F]
char                 ::= [^"\]