grammar

gistfile1.txt

/* Lexer for the mini language */
%lex
%%

\s+                     /* skip whitespace */
"func"                  return 'FUNC';
"return"                return 'RETURN';
"if"                    return 'IF';
"else"                  return 'ELSE';
"while"                 return 'WHILE';
[a-zA-Z_][a-zA-Z_0-9]*  return 'ID';
0|[1-9][0-9]*           return 'NUMBER';
"*"                     return '*';
"/"                     return '/';
"-"                     return '-';
"+"                     return '+';
"^"                     return '^';
"("                     return '(';
")"                     return ')';
"{"                     return '{';
"}"                     return '}';
","                     return ',';
";"                     return ';';
"=="                    return '==';
"="                     return '=';
<<EOF>>                 return 'EOF';
.                       return 'INVALID';

/lex

%left '+' '-'
%left '*' '/' '%'
%left '=='
%left UMINUS

%start program
%%

program
  : root EOF
    { return $1; }
  | EOF
    { return []; }
  ;

root
  : func
    { $$ = [$1]; }
  | root func
    { $1.push($2); $$ = $1; }
  ;

func
  : FUNC ID funcArgsOpt bodyOpt
    { $$ = { 'name': $2, 'args': $3, 'body': $4 }; }
  ;

funcArgsOpt
  : '(' funcArgs ')'
    { $$ = $2; }
  | '(' ')'
    { $$ = []; }
  ;

funcArgs
  : ID
    { $$ = [$1]; }
  | funcArgs ',' ID
    { $1.push($3); $$ = $1; }
  ;

bodyOpt
  : '{' body '}'
    { $$ = $2; }
  | '{' '}'
    { $$ = []; }
  ;

body
  : statement
    { $$ = [$1]; }
  | body statement
    { $1.push($2); $$ = $1; }
  ;

statement
  : return
  | ifElse
  | assignment
  ;

return
  : 'RETURN' expr ';'
    { $$ = { 'op': 'return', 'expr': $2 }; }
  ;

ifElse
  : IF '(' expr ')' bodyOpt ELSE bodyOpt
    { $$ = { 'op': 'if', 'cond': $3, 'true': $5, 'false': $7 }; }
  ;

assignment
  : ID '=' expr ';'
    { $$ = { 'op': 'assign', 'var': $1, 'val': $3 }; }
  ;

expr
  : '(' expr ')'
    { $$ = $2; }
  | expr '+' expr
    { $$ = { 'op': '+', 'lhs': $1, 'rhs': $3 }; }
  | expr '-' expr
    { $$ = { 'op': '-', 'lhs': $1, 'rhs': $3 }; }
  | expr '==' expr
    { $$ = { 'op': 'equ', 'lhs': $1, 'rhs': $3 }; }
  | NUMBER
    { $$ = Number(yytext); }
  | ID callArgsOpt
    { $$ = { 'op': 'call', 'name': $1, 'args': $2 }; }
  | ID
    { $$ = { 'op': 'var', 'name': $1 }; }
  ;

callArgsOpt
  : '(' callArgs ')'
    { $$ = $2; }
  | '(' ')'
    { $$ = []; }
  ;

callArgs
  : expr
    { $$ = [$1]; }
  | callArgs ',' expr
    { $1.push($3); $$ = $1; }
  ;