kit

kit
git clone https://git.ryansepassi.com/git/kit.git
Log | Files | Refs | README

pratt_mixfix.ebnf (883B)

      1 // Mixfix Pratt forms: ternary `?:`, circumfix call/index, and `.` member
      2 // chains layered on the prefix/infix/postfix frame machine.
      3 //
      4 // Precedence is declaration order, loosest first: ternary, then +/-, then */,
      5 // then call `(...)`, then index `[...]`, then `.` member (tightest). Member
      6 // binds tightest so `a.b(c)` is `(a.b)(c)` and `f(x).y` is `(f(x)).y`; call and
      7 // index chain left-to-right at constant depth. The conditional is
      8 // right-associative.
      9 %pratt expr {
     10   primary   primary;
     11   ternary   "?" ":";
     12   infixl    "+" "-";
     13   infixl    "*" "/";
     14   circumfix "(" args ")";
     15   circumfix "[" expr "]";
     16   infixl    ".";
     17 }
     18 
     19 primary = NUMBER | NAME | "(" expr ")";
     20 
     21 // `(` is both a grouping primary-start (nud) and a call open (led); position
     22 // disambiguates. The argument list is comma-separated and may be empty.
     23 args     = %empty | expr arg_more*;
     24 arg_more = "," expr;