Latvian: finally handles PassV2 clauses in a more or less adequate way

Extends the previously introduced support for specifying the verb valence (verb-dependent subject and object cases), involving functions up to PredVP and RelVP.

In Latvian, the passive voice is not used if the agent (subject) is known; to preserve the information structure (i.e. the word order), a clause like 'A is <done> by B' is linearized in the active voice ('A <does> B') where A has the object case (e.g. Acc), and B - the subject case (e.g. Nom). Thus, the verb valence patterns are swapped on-the-fly.

This is still a rather quick & dirty implementation: parameters and linearization types have to be optimized (VerbLav), the use of PassV2 in AdvVP is problematic as it doesn't apply VPSlashPrep / ComplSlash, etc.

lib/src/latvian/RelativeLav.gf

@@ -13,13 +13,29 @@ flags
 lin
   RelCl cl = { s = \\m,p,_ => "ka" ++ cl.s ! m ! p } ;
 
-  RelVP rp vp = {
-    s = \\m,p,ag =>
-      rp.s ! Masc ! Nom ++ 
-      buildVerb vp.v m p (toAgr (fromAgr ag).n P3 (fromAgr ag).g) False vp.objNeg ++ 
-      vp.compl ! ag
-  } ;
+  -- RP -> VP -> RCl
+  RelVP rp vp = mkRelClause rp vp ;
 
+oper
+  -- TODO: PassV2 verbs jāsaskaņo ar objektu, nevis subjektu (by8means_Prep: AgP3 Sg Masc)
+  mkRelClause : RP -> CatLav.VP -> RCl = \rp,vp ->  
+    let subj : Case = case vp.agr.voice of {
+      Act  => vp.agr.c_topic ;
+      Pass => vp.agr.c_focus
+    } in lin RCl {
+      s = \\mood,pol,agr =>
+        case mood of {  -- Subject
+          Deb _ _ => rp.s ! Masc ! Dat ;  --# notpresent
+          _       => rp.s ! Masc ! vp.agr.c_topic
+        } ++
+        case subj of {  -- Verb
+          Nom => buildVerb vp.v mood pol (toAgr (fromAgr agr).num P3 (fromAgr agr).gend) False vp.objNeg ; -- TODO: kāpēc P3 nevis agr, kāds tas ir?
+          _   => buildVerb vp.v mood pol vp.agr.agr False vp.objNeg -- TODO: test me
+        } ++
+        vp.compl ! agr  -- Object(s), complements, adverbial modifiers
+    } ;
+
+lin
   -- FIXME: vārdu secība - nevis 'kas mīl viņu' bet 'kas viņu mīl' (?)
   -- FIXME: Masc varētu nebūt labi
   RelSlash rp slash = {
@@ -29,7 +45,7 @@ lin
   -- FIXME: placeholder
   -- TODO: jātestē, kautkas nav labi ar testpiemēru
   FunRP p np rp = {
-    s = \\g,c => p.s ++ rp.s ! g ! c ++ np.s ! (p.c ! (fromAgr np.a).n)
+    s = \\g,c => p.s ++ rp.s ! g ! c ++ np.s ! (p.c ! (fromAgr np.a).num)
   } ;
 
   IdRP = {