[expr] "raise to power" operator, similar to [pow] function

Returns an integer value if both arguments are integers, and [double]-precision floating-point otherwise.

The left operand may be any integer from Tcl's unlimited integer range.

The right operand is limited to a max integer value of 268435455 (0xfffffff) (28 bits).  (Unless the left operand is -1, 0, or 1, so that the answer is trivial).

Expect to wait a long while for [[expr 2**0xfffffff]] to return.
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**Precedence**
During early 2009, a thread broke out in the comp.lang.tcl usenet group discussing the observation that Tcl's calculation for 

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puts [expr {-2**2}]
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surprised someone who was expecting that to mean

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puts [expr {-(2**2)}
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while Tcl's operator precedence rules cause it to mean

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puts [expr {(-2)**2}
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What this ''does'' mean is that it is consistently possible to interpret `-2` as minus two; no other operators around can change the interpretation.

It also means the answer you get will be different than most, if not all,
other computer programming languages.

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From comp.lang.tcl:

In math: 

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a**0 == 1, a != 0, and 
0**a == 0, a != 0. 
0**0 is an indeterminant 
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In Tcl (8.5.7): 

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expr {0**0} => 1 
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Here is an interesting example which tests the precedence of ** and - 
and demonstrates the right to left application of **: 

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expr {2**-2**2} => 16 
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Force delayed application of -: 

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expr {2.0**-(2**2)} => .0625 
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Force left to right exponentiation: 

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expr {(2.0**-2)**2} => .0625 
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Unambiguous: 

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expr {(2.0)**((-2)**2)} => 16 
===

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!!!!!!
%| [Category Operator] | [Category Command] | [Category Mathematics] |%
!!!!!!