(Eng) Use "whose" in FunRP instead of "of which"

src/english/CatEng.gf

@@ -86,7 +86,12 @@ concrete CatEng of Cat = CommonX - [Pol,CAdv] ** open ResEng, Prelude in {
 
     Conj = {s1,s2 : Str ; n : Number} ;
     Subj = {s : Str} ;
-    Prep = {s : Str; isPre : Bool} ;
+    Prep = {
+        s : Str ;       -- "with", "ago"
+        isPre : Bool ;  -- whether it's pre- or postposition: "with"=True, "ago"=False
+        isPoss : Bool ; -- whether it becomes "whose" in FunRP: "John, whose mother is wise"
+        empty : Str ;   -- dummy empty string to avoid issues with parsing, if s field is replaced by "whose" in FunRP
+        } ;
     CAdv = {s : Polarity => Str; p : Str} ;
 
 -- Open lexical classes, e.g. Lexicon

src/english/ParadigmsEng.gf

@@ -534,10 +534,21 @@ mkVoc s = lin Voc (ss s) ;
 
   mkCAdv sp sn p = lin CAdv {s = table Polarity [sp;sn]; p = p} ;
 
-  mkPrep p = lin Prep {s=p; isPre=True} ;
-  mkPost p = lin Prep {s=p; isPre=False} ;
+  mkPrep p = lin Prep {
+    s = p ;           -- the string: "with", "in front of"
+    isPre = True ;    -- default case: it is a preposition, not postposition
+    isPoss = False ;  -- default case: not possessive (i.e. no change in FunRP)
+    empty = []        -- dummy field to prevent an issue with parsing. only relevant when isPoss=True, and FunRP overrides the s field with "whose". for explanation of the issue, see https://inariksit.github.io/gf/2018/08/28/gf-gotchas.html#metavariables-or-those-question-marks-that-appear-when-parsing
+    } ;
+  mkPost p = mkPrep p ** {
+    isPre = False -- postposition: e.g. "ago"
+    } ;
   noPrep = mkPrep [] ;
 
+  possPrep : Str -> Prep = \p -> mkPrep p ** {
+    isPoss = True -- for possessive, FunRP overrides the Prep's string with "whose":
+    } ;           -- e.g. "whose mother" instead of "mother of which"
+
   mk5V a b c d e = lin V (mkVerb a b c d e ** {s1 = []}) ;
 
   regV cry =

src/english/RelativeEng.gf

@@ -32,8 +32,16 @@ concrete RelativeEng of Relative = CatEng ** open ResEng in {
       c = NPAcc
       } ;
 
+    -- John , whose every friend is right
     FunRP p np rp = {
-      s = \\c => np.s ! NPAcc ++ p.s ++ rp.s ! RPrep (fromAgr np.a).g ;
+      s = \\c =>
+        let npGender : Gender = (fromAgr np.a).g in
+        case p.isPoss of {
+          True  => rp.s ! RC npGender NPNomPoss ++  -- whose
+                   p.empty ++                       -- empty string to avoid metavariables
+                   np.s ! NCase Nom ;               -- NP in nom: "whose every friend"
+          False => np.s ! NPAcc ++ p.s ++ rp.s ! RPrep npGender
+          } ;
       a = RAg np.a
       } ;
 

src/english/StructuralEng.gf

@@ -99,7 +99,7 @@ concrete StructuralEng of Structural = CatEng **
   otherwise_PConj = ss "otherwise" ;
   part_Prep = mkPrep "of" ;
   please_Voc = ss "please" ;
-  possess_Prep = mkPrep "of" ;
+  possess_Prep = possPrep "of" ;
   quite_Adv = mkAdv "quite" ;
   she_Pron = mkPron "she" "her" "her" "hers" singular P3 feminine ;
   so_AdA = mkAdA "so" ;