incr(3tcl)

NAME

   incr - Increment the value of a variable

SYNOPSIS

   incr varName ?increment?
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DESCRIPTION

   Increments the value stored in the variable whose name is varName.  The
   value of the variable must be an integer.   If  increment  is  supplied
   then  its  value  (which  must  be an integer) is added to the value of
   variable varName;  otherwise 1 is added to varName.  The new  value  is
   stored  as  a  decimal  string in variable varName and also returned as
   result.

   Starting with the Tcl 8.5 release, the variable varName passed to  incr 
   may  be  unset, and in that case, it will be set to the value increment 
   or to the default increment value of 1.

EXAMPLES

   Add one to the contents of the variable x:
          incr x

   Add 42 to the contents of the variable x:
          incr x 42

   Add the contents of the variable y to the contents of the variable x:
          incr x $y

   Add nothing at all to the variable x (often useful for checking whether
   an argument to a procedure is actually integral and generating an error
   if it is not):
          incr x 0

SEE ALSO

   expr(3tcl)

KEYWORDS

   add, increment, variable, value

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