Variables being worked on inside of loops

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foreach

foreach(n)						       Tcl Built-In Commands							foreach(n)

__________________________________________________________________________________________________________________________________________________

NAME

       foreach - Iterate over all elements in one or more lists

SYNOPSIS

       foreach varname list body
       foreach varlist1 list1 ?varlist2 list2 ...? body
_________________________________________________________________

DESCRIPTION

       The  foreach command implements a loop where the loop variable(s) take on values from one or more lists.  In the simplest case there is one
       loop variable, varname, and one list, list, that is a list of values to assign to varname.  The body argument is a Tcl  script.	 For  each
       element	of  list  (in  order from first to last), foreach assigns the contents of the element to varname as if the lindex command had been
       used to extract the element, then calls the Tcl interpreter to execute body.

       In the general case there can be more than one value list (e.g., list1 and list2), and each value list can be associated  with  a  list	of
       loop  variables	(e.g.,	varlist1  and varlist2).  During each iteration of the loop the variables of each varlist are assigned consecutive
       values from the corresponding list.  Values in each list are used in order from first to last, and each value is used  exactly  once.   The
       total number of loop iterations is large enough to use up all the values from all the value lists.  If a value list does not contain enough
       elements for each of its loop variables in each iteration, empty values are used for the missing elements.

       The break and continue statements may be invoked inside body, with the same effect as in the for command.  Foreach returns an empty string.

EXAMPLES

       This loop prints every value in a list together with the square and cube of the value:
	      set values {1 3 5 7 2 4 6 8}  ;# Odd numbers first, for fun!
	      puts "Value	Square	Cube"    ;# Neat-looking header
	      foreach x $values {	    ;# Now loop and print...
		  puts " $x	 [expr {$x**2}]	 [expr {$x**3}]"
	      }

       The following loop uses i and j as loop variables to iterate over pairs of elements of a single list.
	      set x {}
	      foreach {i j} {a b c d e f} {
		  lappend x $j $i
	      }
	      # The value of x is "b a d c f e"
	      # There are 3 iterations of the loop.

       The next loop uses i and j to iterate over two lists in parallel.
	      set x {}
	      foreach i {a b c} j {d e f g} {
		  lappend x $i $j
	      }
	      # The value of x is "a d b e c f {} g"
	      # There are 4 iterations of the loop.

       The two forms are combined in the following example.
	      set x {}
	      foreach i {a b c} {j k} {d e f g} {
		  lappend x $i $j $k
	      }
	      # The value of x is "a d e b f g c {} {}"
	      # There are 3 iterations of the loop.

SEE ALSO

       for(n), while(n), break(n), continue(n)

KEYWORDS

       foreach, iteration, list, looping

Tcl																	foreach(n)

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