I'm proposing the addition of the following semantics to Numeric Arrays in order to support indexing arrays using mask and index arrays. Notice that the change required to support this behavior is minimal and all the work can be backloaded to the user. Let the array_subscript C code check to see if the index object passed in is a Tuple with the last element being a callable method. If this is the case, then the C code calls the callable method to handle the array assignment or array indexing code. So, for example one might say. a[a<3,mask] = 10 where mask is a callable method (or Cobject) which does effectively but has the right calling convention. putmask(a, a<3, 10). This same semantics could also handle integer indexing of arrays (using multiple styles). All that's required is a simple test in Numeric that does not break any current code. What do you think? Could I add the necessary check to support this in Numeric? Do others have a better idea? I know numarray is the solution to all of our problems. But, something tells me that the current version of Numeric is going to be around for a little while and it would be nice for it to have some of these useful features. -Travis