dont let string range fool you

[smugindividual]

I have found this to be a problem when using string range to build lists:

The string range function will accept a range outside the bound of the string.

this command:

[string range "happy" 1 4]

would produce "appy" as expected. But these commands:

[string range "happy" -5 -1]
[string range "happy" 4 1]
[string range "happy" 10 20]
[string range "happy" 100 200]

would produce this "".


If i were working my way through a long string and was using lappend to build a list, I might slip past the last letter in the string and start filling my list with a bunch of empties (or {} as they appear in the list).

So if you have a problem with an empty string mysteriously showing up in your list, check to see if you are using string range cammand while building that list.

 

[ulis]

It's a very bad idea to mixt strings and lists.

Yes all is a string in Tcl and a list is a string.
But using a string command for a list is a bad idea (a string command doesn't keep the structure of a list).
Using a list command for a string needs the string to be able to be translated into a list, so to be structured as a list.

I'm not sure to be clear but my experiment is clear: it's definitivly a bad idea.

I hope that some one will give you a strange example where this is an evidence.

Maybe that:

  puts [split {set a [some command]}]
->set a {[some} command\]

ulis

 

[smugindividual]

Ohh, I know its a problem. I was posting this as a helpful hint for others. Just wanted to share the knowledge.