Catch wrong applied field given by user.

integrators/_details/physicalToMathematical.py

@@ -107,6 +107,7 @@ def Compute_Cst(self):
   
 def ConvertAppliedField(self):
   import types
+  from inspect import signature
   from ngsolve import CoefficientFunction, x, y, z
 
   if(self.parameters.H_ext == None):
@@ -122,6 +123,11 @@ def ConvertAppliedField(self):
   hext_mp = [0.0, 0.0, 0.0]
   for d in range(3):
     if isinstance(self.parameters.H_ext[d], types.FunctionType):
+      if(len(signature(self.parameters.H_ext[d]).parameters) != 4):
+        raise ValueError(("H_ext[" + str(d) + "] is a function with " \
+          + str(len(signature(self.parameters.H_ext[d]).parameters)) \
+          + " parameter(s)! --> Error: Needs to depend on exactly 4 parameters" \
+          + " (t, x, y, z) !"))
       hext[d] = self.parameters.H_ext[d](self._time_cf / tScale, x, y, z)
       hext_impl[d] = self.parameters.H_ext[d]( \
         (self._time_cf + self._theta*self._k) / tScale, x, y, z)