Last update: 2005-11-17 17:36:49 CET

Produced by gfdoc - a rudimentary GF document generator. (c) Aarne Ranta (aarne@cs.chalmers.se) 2002 under GNU GPL.

operations for precedence-dependent strings. five levels: p4 (constants), p3 (applications), p2 (products), p1 (sums), p0 (arrows)

        resource Precedence = open Prelude in {

        param
        Prec = p4 | p3 | p2 | p1 | p0 ;

        lintype
        PrecTerm = Prec => Str ;

        oper
        pss : PrecTerm -> {s : PrecTerm} = \s -> {s = s} ;

change this if you want some other type of parentheses

        mkParenth : Str -> Str = \str -> "(" ++ str ++ ")" ;

define ordering of precedences

        nextPrec : Prec => Prec =
          table {p0 => p1 ; p1 => p2 ; p2 => p3 ; _ => p4} ;
        prevPrec : Prec => Prec =
          table {p4 => p3 ; p3 => p2 ; p2 => p1 ; _ => p0} ;

        mkPrec : Str -> Prec => Prec => Str = \str ->
          table {
            p4 => table {                -- use the term of precedence p4...
              _   => str} ;              -- ...always without parentheses
            p3 => table {                -- use the term of precedence p3...
              p4  => mkParenth str ;     -- ...in parentheses if p4 is required...
              _   => str} ;              -- ...otherwise without parentheses
            p2 => table {
              p4  => mkParenth str ;
              p3  => mkParenth str ;
              _   => str} ;
            p1 => table {
              p1  => str ;
              p0  => str ;
              _   => mkParenth str} ;
            p0 => table {
              p0  => str ;
              _   => mkParenth str}
                } ;

make a string into a constant, of precedence p4

        mkConst : Str -> PrecTerm =
          \f ->
          mkPrec f ! p4 ;

make a string into a 1/2/3 -place prefix operator, of precedence p3

        mkFun1 : Str -> PrecTerm -> PrecTerm =
          \f -> \x ->
          table {k => mkPrec (f ++ x ! p4) ! p3 ! k} ;
        mkFun2 : Str -> PrecTerm -> PrecTerm -> PrecTerm =
          \f -> \x -> \y ->
          table {k => mkPrec (f ++ x ! p4 ++ y ! p4) ! p3 ! k} ;
        mkFun3 : Str -> PrecTerm -> PrecTerm -> PrecTerm -> PrecTerm =
          \f -> \x -> \y -> \z ->
          table {k => mkPrec (f ++ x ! p4 ++ y ! p4 ++ z ! p4) ! p3 ! k} ;

make a string into a non/left/right -associative infix operator, of precedence p

        mkInfix : Str -> Prec -> PrecTerm -> PrecTerm -> PrecTerm =
          \f -> \p -> \x -> \y ->
          table {k => mkPrec (x ! (nextPrec ! p) ++ f ++ y ! (nextPrec ! p)) ! p ! k} ;
        mkInfixL : Str -> Prec -> PrecTerm -> PrecTerm -> PrecTerm =
          \f -> \p -> \x -> \y ->
          table {k => mkPrec (x ! p ++ f ++ y ! (nextPrec ! p)) ! p ! k} ;
        mkInfixR : Str -> Prec -> PrecTerm -> PrecTerm -> PrecTerm =
          \f -> \p -> \x -> \y ->
          table {k => mkPrec (x ! (nextPrec ! p) ++ f ++ y ! p) ! p ! k} ;

alternative: precedence as inherent feature

        lintype TermWithPrec = {s : Str ; p : Prec} ;

        oper
        mkpPrec : Str -> Prec -> TermWithPrec =
          \f -> \p ->
          {s = f ; p = p} ;

        usePrec : TermWithPrec -> Prec -> Str =
          \x -> \p ->
          mkPrec x.s ! x.p ! p ;

make a string into a constant, of precedence p4

        mkpConst : Str -> TermWithPrec =
          \f ->
          mkpPrec f p4 ;

make a string into a 1/2/3 -place prefix operator, of precedence p3

        mkpFun1 : Str -> TermWithPrec -> TermWithPrec =
          \f -> \x ->
          mkpPrec (f ++ usePrec x p4) p3 ;

        mkpFun2 : Str -> TermWithPrec -> TermWithPrec -> TermWithPrec =
          \f -> \x -> \y ->
          mkpPrec (f ++ usePrec x p4 ++ usePrec y p4) p3 ;

        mkpFun3 : Str -> TermWithPrec -> TermWithPrec -> TermWithPrec -> TermWithPrec =
          \f -> \x -> \y -> \z ->
          mkpPrec (f ++ usePrec x p4 ++ usePrec y p4 ++ usePrec z p4) p3 ;

make a string a into non/left/right -associative infix operator, of precedence p

        mkpInfix : Str -> Prec -> TermWithPrec -> TermWithPrec -> TermWithPrec =
          \f -> \p -> \x -> \y ->
          mkpPrec (usePrec x (nextPrec ! p) ++ f ++ usePrec y (nextPrec ! p)) p ;
        mkpInfixL : Str -> Prec -> TermWithPrec -> TermWithPrec -> TermWithPrec =
          \f -> \p -> \x -> \y ->
          mkpPrec (usePrec x p ++ f ++ usePrec y (nextPrec ! p)) p ;
        mkpInfixR : Str -> Prec -> TermWithPrec -> TermWithPrec -> TermWithPrec =
          \f -> \p -> \x -> \y ->
          mkpPrec (usePrec x (nextPrec ! p) ++ f ++ usePrec y p) p ;
        } ;