Looping with foreach

The foreach command implements a loop with the variable or variables assigned values from one or more lists and then performs an action. The list or lists may be pre-existing or created as part of the command. This command allows us to perform actions on a list or list of values with minimal effort.

How to do it…

In the following recipe, we will create a Tcl script, to be called from the command line, that recreates the previous recipe by providing hard coded values.

Create a text file named foreach.tcl that contains the following commands.

# First we create a list containing the values to print
set numbers {1 2 3 4 5 6 7 8 9 10}
foreach x $numbers {
puts "x = $x"
}

Now invoke the script using the following command line:

% tclsh85 foreach.tcl
x = 1
x = 2
x = 3
x = 4
x = 5
x = 6
x = 7
x = 8
x = 9
x = 10

How it works…

The action was invoked a total of 10 times as in the previous example. However, as we provided a list to be used, there was no computation required. This is exceptionally...