Filter Math functions that return NaN

src/runtime/providers/math.ts

@@ -24,10 +24,19 @@ abstract class TotalFunctionConstraint extends Constraint {
 
   // Total functions always have a cardinality of 1
   getProposal(tripleIndex, proposed, prefix) {
-    let proposal = this.proposalObject;
-    proposal.providing = proposed;
-    proposal.cardinality = 1;
-    return proposal;
+    if(this.returns.length) {
+      //All except range pass through this function. If isNaN then return.
+      if (isNaN(this.returns[0])){
+        console.log("Returning " + this.returns[0]);
+        return;
+      }
+
+      let proposal = this.proposalObject;
+      proposal.providing = proposed;
+      proposal.cardinality = 1;
+      return proposal;
+    }
+    return;
   }
 }