MidStr (S,l,r) --> cString:
~~~~~~~~~~~~~~~~~~~~~~~~~~~

Functions:
~~~~~~~~~~
Returns a text string S shortened of l-1 character from left and r-1
from right. It returns a middle of the text string from a position l
to a position r.

Parameter description:
~~~~~~~~~~~~~~~~~~~~~~
S:  text string to shorten from both sides
l:  character number to shorten from the left side
r:  character number to shorten from the right side

Return value:
~~~~~~~~~~~~~
shortened string

Example:
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    ? MidStr("1-Hello-21",2,3)  //-Hello- is printed

Source code is in file  Object3.prg