promoteFromMap, promote for tensor products

M2/Macaulay2/m2/enginering.m2

@@ -329,9 +329,13 @@ frac EngineRing := R -> if isField R then R else if R.?frac then R.frac else (
      if R.?indexSymbols then F.indexSymbols = applyValues(R.indexSymbols, r -> promote(r,F));
      if R.?indexStrings then F.indexStrings = applyValues(R.indexStrings, r -> promote(r,F));
      if R.?numallvars then F.numallvars=R.numallvars;
-     scan(R.baseRings, S -> if S.?frac and not isPromotable(S.frac,F) then
-	 promote(S.frac,F) := (a,F) -> fraction(promote(numerator a,R),promote(denominator a,R))
-	 );
+     scan(R.baseRings, S -> if S.?frac and not isPromotable(S.frac,F) then (
+	     promote(S.frac,F) := (a,F) -> fraction(promote(numerator a,R),promote(denominator a,R));
+	     promote(List,S.frac,F) := (m,G,F) -> apply(m, d -> splice ( d | toList(degreeLength F-#d:0) )); -- TODO check
+	     promote(Module,S.frac,F) := (M,G,F) -> F ** M;
+	     promote(Matrix,S.frac,F) := (m,G,F) -> map(promote(target m,F),promote(source m,F),applyTable(entries m,x->promote(x,F)));
+	     promote(MutableMatrix,S.frac,F) := (m,G,F) -> mutableMatrix applyTable(entries m,x->promote(x,F));
+	     ));
      F)
 
 -- methods for all ring elements

M2/Macaulay2/m2/exports.m2

@@ -1028,6 +1028,7 @@ export {
 	"projectiveHilbertPolynomial",
 	"programPaths",
 	"promote",
+	"promoteFromMap",
 	"protect",
 	"prune",
 	"pruningMap",

M2/Macaulay2/m2/matrix.m2

@@ -166,9 +166,9 @@ Matrix * Matrix := Matrix => (m,n) -> (
      else (
      	  R := ring m;
 	  S := ring target n;
-	  if R =!= S then (
-	       try m = m ** S else
-	       try n = n ** R else
+	  if R =!= S then ( -- use toSameRing?
+	       try m = promote(m,S) else
+	       try n = promote(n,R) else
 	       error "maps over incompatible rings";
 	       );
 	  M = target m;

M2/Macaulay2/m2/newring.m2

@@ -11,6 +11,18 @@ needs "matrix2.m2" -- for lift
 -- new polynomial ring or quotient ring from old --
 ----------------------------------
 
+-- automate promotion
+promoteFromMap = method()
+promoteFromMap (Ring,Ring,RingMap) := (R,S,f) -> (
+    promote(R,S) := (a,S1) -> f a;
+    promote(Matrix,R,S) :=
+    promote(MutableMatrix,R,S) := -- doesn't work, cf https://github.com/Macaulay2/M2/issues/2192
+    promote(Module,R,S) := (M,R1,S1) -> f M; -- TODO rethink carefully
+--    promote(List,R,S) := (L,R1,S1) -> f\L; -- TODO put back!!!!!!!!!!
+    )
+promoteFromMap (Ring,Ring) := (R,S) -> promoteFromMap(R,S,map(S,R))
+
+
 -- TODO: rewrite this to be easier to manage with degree group
 nothing := symbol nothing
 newRing = method( Options => applyValues(monoidDefaults, x -> nothing), TypicalValue => Ring )
@@ -77,7 +89,11 @@ tensor(QuotientRing,   QuotientRing) := monoidTensorDefaults >> optns -> (R, S)
      fg := substitute(f,(vars AB)_{0 .. m-1}) | substitute(g,(vars AB)_{m .. m+n-1});
      -- forceGB fg;  -- if the monomial order chosen doesn't restrict, then this
                      -- is an error!! MES
-     AB/image fg)
+     RS := AB/image fg;
+     promoteFromMap(R,RS,map(RS,R,(vars AB)_{0 .. m-1}));
+     promoteFromMap(S,RS,map(RS,S,(vars AB)_{m .. m+n-1}));
+     RS
+     )
 
 -------------------------
 -- Graph of a ring map --

M2/Macaulay2/packages/CotangentSchubert/cotangent.m2

@@ -61,18 +61,6 @@ expandElem := (P,vrs,els) -> (
     sub(C,ring first els) * product(#vrs, i -> (els#i)^(ee#i)) + expandElem(Q,vrs,els)
     )
 
--- automate promotion
-promoteFromMap = method()
-promoteFromMap (Ring,Ring,RingMap) := (R,S,f) -> (
-    promote(R,S) := (a,S1) -> f a;
-    promote(Matrix,R,S) :=
-    promote(MutableMatrix,R,S) := -- doesn't work, cf https://github.com/Macaulay2/M2/issues/2192
-    promote(Module,R,S) := (M,R1,S1) -> f M;
---    promote(List,R,S) := (L,R1,S1) -> f\L; -- TODO put back!!!!!!!!!!
-    S.baseRings = prepend(R,S.baseRings); -- temporary -- until promotability test improved in enginering.m2
-    )
-promoteFromMap (Ring,Ring) := (R,S) -> promoteFromMap(R,S,map(S,R))
-
 tautoClass = method(Dispatch=>{Thing,Thing,Type},Options=>true); -- "Chern classes" -- renamed tautoClass to avoid confusion with motivic classes
 zeroSection = method(Dispatch=>{Type},Options=>true) -- note the {}
 dualZeroSection = method(Dispatch=>{Type},Options=>true) -- note the {}