For 2021 - online Python 3 training - see ((here)).
Our plans were to retire in summer 2020 and see the world, but Coronavirus has lead us into a lot of lockdown programming in Python 3 and PHP 7. We can now offer tailored online training - small groups, real tutors - works really well for groups of 4 to 14 delegates. Anywhere in the world; course language English.
Please ask about private 'maintenance' training for Python 2, Tcl, Perl, PHP, Lua, etc. |
Everything is a string - even a list
Almost all variables in Tcl are held as strings ... if you use integers and stirings in calculations such as expr and incr. the strings are converted back and forth intergally. Lists, too, are held as strings of characters in which chunks of string are counted / taken out as being elements in the list. Here's an example setting up a list ... and then reporting the length as a list (where it contains two values), and as a string (where it contains 15 letters).
% set daze "Monday Chewsday"
Monday Chewsday
% puts daze
daze
% puts $daze
Monday Chewsday
% put [string length $daze]
15
% put [llength $daze]
2
%
Note my use of almost - Tcl's arrays are NOT held as simple strings - and that does make a difference (later in Tcl course we'll take a look at this) (written 2015-03-11)
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles T206 - Tcl/Tk - Lists [144] Tcl sandwich - lists in Tcl - (2004-12-08) [463] Splitting the difference - (2005-10-13) [781] Tcl - lappend v concat - (2006-06-27) [1282] Stringing together Tcl scripts - (2007-07-29) [1283] Generating traffic for network testing - (2007-07-29) [1334] Stable sorting - Tcl, Perl and others - (2007-09-06) [1402] Tcl - append v lappend v concat - (2007-10-23) [1405] Sorting in Tcl - lists and arrays - (2007-10-24) [1601] Replacing the last comma with an and - (2008-04-04) [2468] What are Tcl lists? - (2009-10-22) [2472] split and join in tcl and expect - (2009-10-23) [3285] Extracting data from a string / line from file - Tcl - (2011-05-10) [3394] The difference between lists and strings - Tcl - (2011-08-16) [3415] User defined sorting and other uses of callbacks in Tcl and Tk - (2011-09-02) [3582] Tcl collections - lists, dicts and array - (2012-01-16) [3583] Expanding a list of parameters in Tcl - {*} and eval - (2012-01-17) [3618] lists and struct::list in Tcl - Introduction to struct::list and examples - (2012-02-18) [4209] Lists in Tcl - fundamentals in a commented source code example - (2013-11-16) [4455] Working out distance between places, using OS grid references and a program in Tcl - (2015-03-11) T205 - Tcl/Tk - String Handling in Tcl [404] How to check that a string contains a number in Tcl - (2005-08-06) [779] The fragility of pancakes - and better structures - (2006-06-26) [943] Matching within multiline strings, and ignoring case in regular expressions - (2006-11-25) [1403] Square Bracket protection in Tcl - (2007-10-23) [1410] Tcl / regsub - changing a string and using interesting bits - (2007-10-27) [3192] Tcl - Some example of HOW TO in handling data files and formats - (2011-03-04) [3576] Tcl - apparently odd behaviour of string trimleft - (2012-01-13) [4205] Regular Expression Substitution - Tcl - (2013-11-12)
Some other Articles
A new Tcl/tk example - a window to show system statusTest framework for TCL - Tcltest - some examplesObjects in Tcl - iTcl - updated first steps exampleEverything is a string - even a listTcl variable names - no real limits!Binary data handling - Python and PerlRunning an operating system command from your Python program - the new way with the subprocess moduleDeciding whether to use parameters, conditional statements or subclassesSpike solution, refactoring into encapsulated object methods - good design practise
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This is a page archived from The Horse's Mouth at
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