foreach(n) Tcl Built-In Commands foreach(n) ______________________________________________________________________________ NAME foreach - Iterate over all elements in one or more lists SYNOPSISforeachvarname list bodyforeachvarlist1 list1?varlist2 list2 ...?body______________________________________________________________________________ DESCRIPTION Theforeachcommand 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 tovarname. Thebodyargument is a Tcl script. For each element oflist(in order from first to last),foreachassigns the contents of the element tovarnameas if thelindexcommand had been used to extract the element, then calls the Tcl interpreter to executebody. In the general case there can be more than one value list (e.g.,list1andlist2), and each value list can be associated with a list of loop variables (e.g.,varlist1andvarlist2). During each iteration of the loop the variables of eachvarlistare assigned consecutive values from the correspondinglist. Values in eachlistare 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. Thebreakandcontinuestatements may be invoked insidebody, with the same effect as in theforcommand.Foreachreturns 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\tSquare\tCube" ;# Neat-looking headerforeachx $values { ;# Now loop and print... puts " $x\t [expr {$x**2}]\t [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 {}foreachi {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 {}foreachi {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, loop Tcl foreach(n)