Tcl/Tk - Arrays and dicts

Tcl/Tk module T208

Arrays and dicts

Exercises, examples and other material relating to training module T208. This topic is presented on public courses Learning to program in Tcl, Tcl Programming, Tcl Programming

Background

Arrays are variables that can contain a number of strings, and each one can be looked up by its index and key. Unlike arrays in other languages, array keys in Tcl are strings, not integers, and array members can contain strings of differing lengths. Dicts are an alternative to arrays that implement unordered, keyed collections through strings. You'll start this module learning about the basics of arraysi and dicts, and go on to learn some of the wider uses and extra power that's provided by their somewhat unusual specification, taught by example.

Examples from our training material

ar1	First use of arrays
ar2	Checking if an array key exists
ar3	looping though an array with array get
ar_rail	Setting up an array and sorting the elements by key
arr_log	Access log counter using arrays
arr_log_2	Selecting elements from an array - glob matching to keys
arr_log_3	Passing arrays in and out of procs - using upvar
au	Demo of use of upvar
dicdem	dicts - using the various subcommands
dict1	setting up and get, dict
dict2	Conrol - using a string as a list
dict3	iterating through the keys of a dict
dict4	dict for
dla	list, array, dict
dnicer	test program for station data
ifinder	search for icon references; list icon names
ifinder2	search for icon references and count them
mini	2nd program using railutils
nested	nested dicts
rail_dict	Sorting a dict
railutils	File of procs to do with station info
stfinal	final exercise - array of dialling codes
topskill	setting up an array of lists, sorting, listing out elements

Pictures

Arrays in Tcl
A small group learns Tcl on a private course

Background information

Some modules are available for download as a sample of our material or under an Open Training Notes License for free download from [here].

Topics covered in this module

First use of an array.
Setting up an array.
Referencing elements of an array.
Enquiring on an array.
First use of a dict.
Pure and impure variables.
Arrays rather than lists or dicts.
A wider range of array commands.
Array get and set.
Selecting elements from an array.
Uses of arrays.
Using numeric indexes.
Passing arrays to procs.
Unique keys.

Complete learning

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