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OpenDarwin 7.2.1 - man page for lset (opendarwin section n)

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

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NAME
       lset - Change an element in a list

SYNOPSIS
       lset varName ?index...? newValue
_________________________________________________________________

DESCRIPTION
       The  lset command accepts a parameter, varName, which it interprets as the name of a vari-
       able containing a Tcl list.  It also accepts zero or more  indices  into  the  list.   The
       indices	may  be  presented  either consecutively on the command line, or grouped in a Tcl
       list and presented as a single argument.  Finally, it accepts a new value for  an  element
       of varName.

       If no indices are presented, the command takes the form:
	      lset varName newValue
       or
	      lset varName {} newValue
       In this case, newValue replaces the old value of the variable varName.

       When  presented	with  a  single index, the lset command treats the content of the varBane
       variable as a Tcl list.	It addresses the index'th element in it (0 refers  to  the  first
       element of the list).  When interpreting the list, lset observes the same rules concerning
       braces and quotes and backslashes as the Tcl command interpreter; however,  variable  sub-
       stitution  and  command	substitution  do not occur.  The command constructs a new list in
       which the designated element is replaced with newValue.	This new list is  stored  in  the
       variable varName, and is also the return value from the lset command.

       If  index is negative or greater than or equal to the number of elements in $varName, then
       an error occurs.

       If index has the value end, it refers to the last element in  the  list,  and  end-integer
       refers to the last element in the list minus the specified integer offset.

       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 alter elements in sublists.  The command,
	      lset a 1 2 newValue
       or
	      lset a {1 2} newValue
       replaces element 2 of sublist 1 with newValue.

       The  integer  appearing in each index argument must be greater than or equal to zero.  The
       integer appearing in each index argument must be strictly less than the length of the cor-
       responding  list.   In other words, the lset command cannot change the size of a list.  If
       an index is outside the permitted range, an error is reported.

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 return value also becomes the new value of x (except in the last case, which
       is an error which leaves the value of x unchanged.)
	      lset x {j k l} => j k l
	      lset x {} {j k l} => j k l
	      lset x 0 j => j {d e f} {g h i}
	      lset x 2 j => {a b c} {d e f} j
	      lset x end j => {a b c} {d e f} j
	      lset x end-1 j => {a b c} j {g h i}
	      lset x 2 1 j => {a b c} {d e f} {g j i}
	      lset x {2 1} j => {a b c} {d e f} {g j i}
	      lset 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 return value also becomes the new value of x.
	      lset x 1 1 0 j => {{a b} {c d}} {{e f} {j h}}
	      lset x {1 1 0} j => {{a b} {c d}} {{e f} {j h}}

SEE ALSO
       list(n),  lappend(n),  lindex(n), linsert(n), llength(n), lsearch(n), lsort(n), lrange(n),
       lreplace(n)

KEYWORDS
       element, index, list, replace, set

Tcl					       8.4					  lset(n)
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