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# overlay(+MapA, +MapB, -Map)

Overlays one map over another.

MapA
  A map
MapB
  The map to overlay
Map
  The resulting map

## Description

The map Map contains a key/value pair for every key that appears in either the map MapA or the map MapB. If a key Key appears in MapB, then its corresponding value in Map is that appearing in MapB; otherwise it is that appearing in MapA.

This predicate should only be called with maps created by other predicates from the map module.

### Fail Conditions

Never fails.

### Resatisfiable

no

## See Also

merge / 3