UnsupportedTokenGluing.gf

abstract UnsupportedTokenGluing = {
flags startcat = S ;
cat
  S ; A ;
fun
  toS : A -> S ;
  a,b : A ;
}

UnsupportedTokenGluingCnc.gf

concrete UnsupportedTokenGluingCnc of UnsupportedTokenGluing = open Predef in {
lincat S, A = Str ;
lin

{- Unsupported token gluing:
 toS = addA ;
 a = "" ;
-}

{-gf: Internal error in GeneratePMCFG:
 toS = checkB ;
 a = "a" ; b = "b" ;
-}

 toS x = x;
 a = addA "" ; -- this works, because the token from addA isn't glued at runtime. `a` is a 0-argument function, it is *created* by addA.

 b = checkB "b" ; -- this works, because the token from checkB isn't checked at runtime. `b` is a 0-argument function, it is *created* by checkB.

oper

addA : Str -> Str = \s -> s + "a" ;

checkB : Str -> Str = \s -> case s of {
  "b" => "your string was b" ;
  _   => "your string wasn't b" } ;
}

Minimal example for explaining the GF error message "unsupported token gluing"