====== Tcl string concatenation ====== This page is part of the Tcl/Tk page of the Airplug documentation.\\ [[en:doc:pub:tcltk:start|Back to the Tcl/Tk page]] / [[en:doc:summary|Back to Airplug documentation page]]. --- * Two string variables can easily be concatenated as follows:


set alpha "Hel"
set beta "lo"
puts stdout $alpha$beta

This gives:


Hello

* Another way is to use ''append'':


set alphabeta "Hel"
append alphabeta "lo"
puts stdout $alpha$beta

This gives:


Hello

* However, when mixing a string variable and a literal string, the result is not what would be expected:


set alpha "Hel"
puts stdout $alpha"Hel"

This gives:


Hel"lo"

* It is important to note that the ''concat'' tcl function applies on lists. It is possible to concat some strings by using a list but this is not the good way:


set alphabeta [concat "Hel" "lo"]
puts stdout $alphabeta

This gives a list of two members, displayed with a space between them:


Hel lo

A list can be merged to give a string (here without spaces between members) as follows:


set alphabeta [join [concat "Hel" "lo"] ""
puts stdout $alphabeta

This gives:


Hello

However this is not efficient. * Finally, the simplest way is by using curly braces to separate the variable name:


set alpha "Hel"
set alphabeta ${alpha}lo
puts stdout $alphabeta

This gives:


Hello

* **Conclusion**: * With ''append'':


set alphabeta "Hel"
append alphabeta "lo"

* With curly braces:


set alpha "Hel"
set alphabeta ${alpha}lo

---- This page is part of the Tcl/Tk page of the Airplug documentation.\\ [[en:doc:pub:tcltk:start|Back to the Tcl/Tk page]] / [[en:doc:summary|Back to Airplug documentation page]].