fix: resolves #646 for euler sums without arguments.

Author: cbmarini

check/fixes.frm

@@ -3925,6 +3925,16 @@ Print;
 assert succeeded?
 assert result("F") =~ expr("0")
 *--#] Issue642 :
+*--#[ Issue646 :
+#StartFloat 30
+Local F = mzv_+euler_+mzvhalf_;
+Evaluate;
+Print;
+.end
+#pend_if wordsize == 2
+assert succeeded?
+assert result("F") =~ expr("mzv_ + euler_ + mzvhalf_")
+*--#] Issue646 :
 *--#[ Issue695_1 :
 #StartFloat 20
 CFunction f;

sources/float.c

@@ -2343,6 +2343,8 @@ int EvaluateEuler(PHEAD WORD *term, WORD level, WORD par)
 				sumweight += ABS(tt[1]); depth++;
 				tt += 2;
 			}
+			/* euler sum without arguments, i.e. mzv_(), euler_() or mzvhalf_() */
+			if ( depth == 0) goto nextfun;
 			if ( sumweight > AC.MaxWeight ) {
 				MesPrint("Error: Weight of Euler/MZV sum greater than %d",sumweight);
 				MesPrint("Please increase MaxWeight in form.set.");