grammar.md

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This is the grammar of the C Star (C*) programming language.

C* is a tiny subset of the programming language C. C* features global variable declarations with optional initialization as well as procedures with parameters and local variables. C* has five statements (assignment, while loop, if-then-else, procedure call, and return) and standard arithmetic (+, -, *, /, %) and comparison (==, !=, <, <=, >, >=) operators. C* includes the unary * operator for dereferencing pointers hence the name but excludes data types other than uint64_t and uint64_t*, bitwise and Boolean operators, and many other features. The C* grammar is LL(1) with 6 keywords and 22 symbols. Whitespace as well as single-line (//) and multi-line (/* to */) comments are ignored.

C* Keywords: uint64_t, void, if, else, while, return

C* Symbols: integer_literal, character_literal, string_literal, identifier, ,, ;, (, ), {, }, +, -, *, /, %, =, ==, !=, <, <=, >, >=

with:

integer_literal   = digit { digit } .

character_literal = "'" printable_character "'" .

string_literal    = """ { printable_character } """ .

identifier        = letter { letter | digit | "_" } .

and:

digit  = "0" | ... | "9" .

letter = "a" | ... | "z" | "A" | ... | "Z" .

C* Grammar:

cstar             = { type identifier
                      [ "=" [ cast ] [ "-" ] ( integer_literal | character_literal ) ] ";" |
                    ( "void" | type ) identifier procedure } .

type              = "uint64_t" [ "*" ] .

cast              = "(" type ")" .

procedure         = "(" [ variable { "," variable } ] ")" ( ";" |
                    "{" { variable ";" } { statement } "}" ) .

variable          = type identifier .

statement         = ( [ "*" ] identifier | "*" "(" expression ")" ) "=" expression ";" |
                    call ";" | while | if | return ";" .

call              = identifier "(" [ expression { "," expression } ] ")" .

expression        = simple_expression
                    [ ( "==" | "!=" | "<" | ">" | "<=" | ">=" ) simple_expression ] .

simple_expression = term { ( "+" | "-" ) term } .

term              = factor { ( "*" | "/" | "%" ) factor } .

factor            = [ cast ] [ "-" ] [ "*" ]
                    ( integer_literal | character_literal | string_literal |
                      identifier | call | "(" expression ")" ) .

while             = "while" "(" expression ")"
                      ( statement | "{" { statement } "}" ) .

if                = "if" "(" expression ")"
                      ( statement | "{" { statement } "}" )
                    [ "else"
                      ( statement | "{" { statement } "}" ) ] .

return            = "return" [ expression ] .