NAME

       lpop - Get and remove an element in a list

SYNOPSIS

       lpop varName ?index ...?
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DESCRIPTION

       The lpop command accepts a parameter, varName, which it interprets as the name of a variable containing a
       Tcl list.  It also accepts one or more indices into the list. If no indices are presented, it defaults to
       "end".

       When  presented  with  a  single index, the lpop command addresses the index'th element in it, removes if
       from the list and returns the element.

       If index is negative or greater or equal than the number of elements in the list in the  variable  called
       varName, an error occurs.

       The  interpretation  of  each  simple index value is the same as for the command string index, supporting
       simple index arithmetic and indices relative to the end of the list.

       If additional index arguments are supplied, then each argument is used in  turn  to  address  an  element
       within a sublist designated by the previous indexing operation, allowing the script to remove elements in
       sublists, similar to lindex and lset.  The command,

              lpop a 1 2

       gets and removes element 2 of sublist 1.

EXAMPLES

       In each of these examples, the initial value of x is:

              set x [list [list a b c] [list d e f] [list g h i]]
                    → {a b c} {d e f} {g h i}

       The  indicated  value becomes the new value of x (except in the last case, which is an error which leaves
       the value of x unchanged.)

              lpop x 0
                    → {d e f} {g h i}
              lpop x 2
                    → {a b c} {d e f}
              lpop x end
                    → {a b c} {d e f}
              lpop x end-1
                    → {a b c} {g h i}
              lpop x 2 1
                    → {a b c} {d e f} {g i}
              lpop x 2 3 j
                    → list index out of range

       In the following examples, the initial value of x is:

              set x [list [list [list a b] [list c d]] \
                          [list [list e f] [list g h]]]
                    → {{a b} {c d}} {{e f} {g h}}

       The indicated value becomes the new value of x.

              lpop x 1 1 0
                    → {{a b} {c d}} {{e f} h}

SEE ALSO

       list(3tcl),  lappend(3tcl),  lassign(3tcl),  ledit(3tcl),  lindex(3tcl),  linsert(3tcl),   llength(3tcl),
       lmap(3tcl),  lrange(3tcl),  lremove(3tcl),  lrepeat(3tcl), lreplace(3tcl), lreverse(3tcl), lsearch(3tcl),
       lseq(3tcl), lset(3tcl), lsort(3tcl), string(3tcl)

KEYWORDS

       element, index, list, remove, pop, stack, queue

Tcl                                                    9.0                                            lpop(3tcl)