'''`[dict] unset`''' removes a key and its associated value from a dictionary
of dictionaries.



** Attributes **

    from Tcl version:   [Changes in Tcl/Tk 8.5%|%8.5]



** Synopsis **

    :   '''dict unset''' ''dictVarName key'' ?''key''?



** Description **

`[dict] unset` unsets one element from the dictionary of dictionaries named
''dictVarName''.  They ''key'' arguments form a path to the key to unset. 
The variable is modified, and its new value is returned.  If the given ''key'' doesn't exist in the dict, no change is made.  If a key path is given, all keys except the last must exist.

======
% # Simple example:
% set data {a 1 b 2}
a 1 b 2
% dict unset data a ;# Remove key "a" and its corresponding value "1"
b 2
% set data ;# Verify that variable is modified.
b 2
% dict unset data nonexistent ;# Check nonexistent key handling
b 2
======
======
% # Example using nested dicts:
% set data {row1 {col1 val11 col2 val12} row2 {col1 val21 col2 val22}}
row1 {col1 val11 col2 val12} row2 {col1 val21 col2 val22}
% dict unset data row2 col2 ;# Remove element "col2" in nested dict "row2"
row1 {col1 val11 col2 val12} row2 {col1 val21}
% dict unset data row1 ;# Remove element "row1"
row2 {col1 val21}
% set data ;# Verify again that variable is modified
row2 {col1 val21}
% dict unset data row2 col2 ;# Check nonexistent key handling
row2 {col1 val21}
% dict unset data row1 col2 ;# Check nonexistent nested dict handling
key "row1" not known in dictionary
======

----

A synonym for 

======
dict unset dictname key
======
is

===
[dict update] dictname key key {unset key}
===

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