Chapter 5. Tcl Lists

This chapter describes Tcl lists. Tcl commands described are: list, lindex, llength, lrange, lappend, linsert, lreplace, lsearch, lset, lsort, concat, join, and split.

Lists in Tcl have the same structure as Tcl commands. All the rules you learned about grouping arguments in Chapter 1 apply to creating valid Tcl lists. However, when you work with Tcl lists, it is best to think of lists in terms of operations instead of syntax. Tcl commands provide operations to put values into a list, get elements from lists, count the elements of lists, replace elements of lists, and so on. It is a good habit to use commands like list and lappend to construct lists, instead of creating them by hand. Lists are used with commands such as foreach that take lists as arguments. In addition, lists are important when you are building up a command to be evaluated later. Delayed command evaluation with eval is described in Chapter 10, and similar issues with Tk callback commands are described in Chapter 30.

However, Tcl lists are not often the right way to build complicated data structures in scripts. You may find Tcl arrays more useful, and they are the topic of Chapter 8. List operations are also not right for handling unstructured data such as user input. Use regular expressions instead, which are described in Chapter 11.