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



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NAME
     foreach - Iterate over all elements in one or more lists

SYNOPSIS
     foreach _v_a_r_n_a_m_e _l_i_s_t _b_o_d_y
     foreach _v_a_r_l_i_s_t_1 _l_i_s_t_1 ?_v_a_r_l_i_s_t_2 _l_i_s_t_2 ...? _b_o_d_y
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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, _v_a_r_n_a_m_e,  and  one
     list,  _l_i_s_t,  that is a list of values to assign to _v_a_r_n_a_m_e.
     The _b_o_d_y argument is a Tcl script.  For each element of _l_i_s_t
     (in  order from first to last), foreach assigns the contents
     of the element to _v_a_r_n_a_m_e as if the lindex command had  been
     used  to extract the element, then calls the Tcl interpreter
     to execute _b_o_d_y.

     In the general case there can be more than  one  value  list
     (e.g.,  _l_i_s_t_1 and _l_i_s_t_2), and each value list can be associ-
     ated with a list of loop variables (e.g., _v_a_r_l_i_s_t_1 and  _v_a_r_-
     _l_i_s_t_2).   During each iteration of the loop the variables of
     each  _v_a_r_l_i_s_t  are  assigned  consecutive  values  from  the
     corresponding  _l_i_s_t.   Values in each _l_i_s_t 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 vari-
     ables in each iteration, empty values are used for the miss-
     ing elements.

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

EXAMPLES
     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.






Tcl                       Last change:                          1






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



     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.


KEYWORDS
     foreach, iteration, list, looping
































Tcl                       Last change:                          2