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# update(+Tree0, ++Key, ?Value, -Tree)

Update the value corresponding to a key in a tree.

Tree0
  A 2-3-4 tree
Key
  A key to update
Value
  The value corresponding to Key
Tree
  The tree after updating

## Description

If the key Key already exists in the tree Tree0, then this predicate updates the corresponding value to be Value. The resulting tree is Tree.

This predicate should only be called with trees created by other predicates from the tree234 module.

### Fail Conditions

Fails if Key does not appear in Tree0.

### Resatisfiable

no

## See Also

insert / 4, set / 4