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aee12d700d
Add enum production rules to the EBNF grammar. Add comprehensive enum section to the cheatsheet covering syntax, explicit values, underlying type specification, construction, to_underlying, comparison, type-safe dispatch, and switch usage. Document that the underlying type must be a numeric type (string cannot be used) and list all available types. Requested by @lefticus in PR #679 review. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
189 lines
6.2 KiB
EBNF
189 lines
6.2 KiB
EBNF
/*
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* ChaiScript Grammar — EBNF for Railroad Diagram Generation
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*
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* View as navigable railroad diagrams at:
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* https://www.bottlecaps.de/rr/ui (IPv6)
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* https://rr.red-dove.com/ui (IPv4)
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*
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* Copy and paste this file into the 'Edit Grammar' tab, then
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* click 'View Diagram'.
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*
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* This grammar uses the notation accepted by
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* https://github.com/GuntherRademacher/rr :
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* - "::=" as rule separator
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* - no semicolon at end of rule
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* - "?" "+" "*" for repetition
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* - C comments
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*/
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/* ---- Top-level ---- */
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statements ::= ( def | try | if | while | class | enum
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| for | switch | return | break | continue
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| equation | block | eol )+
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/* ---- Functions ---- */
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def ::= "def" id ( "::" id )? "(" decl_arg_list ")" eol*
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( ":" guard )? eol* block
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lambda ::= "fun" ( "[" id_arg_list "]" )? "(" decl_arg_list ")" eol* block
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guard ::= operator
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/* ---- Exception handling ---- */
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try ::= "try" eol* block catch* finally?
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catch ::= "catch" ( "(" arg ")" )? eol* block
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finally ::= "finally" eol* block
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/* ---- Control flow ---- */
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if ::= "if" "(" equation ( eol equation )? ")" eol* block
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( "else" ( if | eol* block ) )*
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while ::= "while" "(" operator ")" eol* block
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for ::= "for" "(" ( for_guards | equation ":" equation ) ")" eol* block
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for_guards ::= equation eol equation eol equation
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switch ::= "switch" "(" operator ")" eol* "{" ( case | default )+ "}"
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case ::= "case" "(" operator ")" eol* block
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default ::= "default" eol* block
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/* ---- Classes ---- */
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class ::= "class" id ( ":" id )? eol* class_block
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class_block ::= "{" class_statements* "}"
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class_statements ::= def | var_decl | eol
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/* ---- Enums ---- */
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enum ::= "enum" ( "class" | "struct" ) id ( ":" underlying_type )?
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"{" enum_entries? "}"
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enum_entries ::= enum_entry ( "," enum_entry )*
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enum_entry ::= id ( "=" integer )?
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underlying_type ::= id
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/* ---- Blocks & flow keywords ---- */
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block ::= "{" statements* "}"
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return ::= "return" operator?
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break ::= "break"
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continue ::= "continue"
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/* ---- Line termination ---- */
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eol ::= "\n" | "\r\n" | ";"
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/* ---- Equations & operators ---- */
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equation ::= operator ( ( "=" | ":=" | "+=" | "-=" | "*=" | "/="
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| "%=" | "<<=" | ">>=" | "&=" | "^=" | "|=" )
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equation )?
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operator ::= prefix
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| value
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| operator binary_operator operator
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| operator "?" operator ":" operator
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prefix ::= ( "++" | "--" | "-" | "+" | "!" | "~" ) operator
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binary_operator ::= "||" | "&&"
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| "|" | "^" | "&"
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| "==" | "!="
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| "<" | "<=" | ">" | ">="
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| "<<" | ">>"
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| "+" | "-"
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| "*" | "/" | "%"
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/* ---- Values & access ---- */
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value ::= var_decl | dot_fun_array | prefix
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dot_fun_array ::= ( lambda | num | quoted_string
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| single_quoted_string | raw_string
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| paren_expression | inline_container
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| id )
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( fun_call | array_call | dot_access )*
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fun_call ::= "(" arg_list ")"
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array_call ::= "[" operator "]"
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dot_access ::= "." id
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/* ---- Variable declarations ---- */
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var_decl ::= ( "auto" | "var" | "const" ) ( reference | id )
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| "global" ( reference | id )
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| "attr" id ( "::" id )?
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reference ::= "&" id
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/* ---- Parenthesised & inline containers ---- */
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paren_expression ::= "(" operator ")"
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inline_container ::= "[" container_arg_list "]"
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container_arg_list ::= value_range
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| map_pair ( "," map_pair )*
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| operator ( "," operator )*
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value_range ::= operator ".." operator
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map_pair ::= operator ":" operator
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/* ---- String literals ---- */
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quoted_string ::= '"' ( char | escape | interpolation )* '"'
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single_quoted_string ::= "'" ( char | escape ) "'"
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raw_string ::= 'R"' delimiter? "(" char* ")" delimiter? '"'
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delimiter ::= [a-zA-Z0-9_]+
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interpolation ::= "${" equation "}"
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/* ---- Escape sequences ---- */
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escape ::= "\" ( "'" | '"' | "?" | "\" | "a" | "b"
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| "f" | "n" | "r" | "t" | "v" | "$"
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| "0"
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| "x" hex_digit+
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| "u" hex_digit hex_digit hex_digit hex_digit
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| "U" hex_digit hex_digit hex_digit hex_digit
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hex_digit hex_digit hex_digit hex_digit
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| octal_digit+ )
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/* ---- Argument lists ---- */
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id_arg_list ::= id ( "," id )*
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decl_arg_list ::= ( arg ( "," arg )* )?
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arg_list ::= ( equation ( "," equation )* )?
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arg ::= id id?
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/* ---- Identifiers ---- */
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id ::= ( [a-zA-Z_] [a-zA-Z0-9_]* )
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| ( "`" [^`]+ "`" )
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| "true" | "false"
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| "Infinity" | "NaN"
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| "_"
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| "__LINE__" | "__FILE__" | "__FUNC__" | "__CLASS__"
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/* ---- Numeric literals ---- */
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num ::= hex | binary | float | integer
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hex ::= "0" ( "x" | "X" ) [0-9a-fA-F]+ int_suffix*
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binary ::= "0" ( "b" | "B" ) [01]+ int_suffix*
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float ::= [0-9]+ "." [0-9]+ ( ( "e" | "E" ) ( "+" | "-" )? [0-9]+ )? float_suffix?
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integer ::= [0-9]+ int_suffix*
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int_suffix ::= "l" | "L" | "ll" | "LL" | "u" | "U"
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float_suffix ::= "l" | "L" | "f" | "F"
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/* ---- Character classes ---- */
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octal_digit ::= [0-7]
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hex_digit ::= [0-9a-fA-F]
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char ::= [^"\]
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