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Comment by gecko | Hacker News Reader

The way I'm used to seeing the GP's example made is

    set a pu
    set b ts
    $a$b "Hello!"

which I think does a better job showing how the mixture of strings with interpolation allows for some slightly unexpected things.

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Yes, you're probably right. Frankly, I'd rather not have this kind or error-prone behavior in my programming languages, not even when scripting. It makes proper handling of strings hard and cumbersome (as evidenced by a lot of software that can't handle spaces in file names because it's calling scripts written in sh or bash), and I don't get the Tcl love professed in the comments here.

I'm not a fan of Tcl -- I used it a bit in the 90's -- but this really isn't the best example. You need a bit more context to give it a fair shake.

This is kind of clumsy in R5RS Scheme:

    ((eval (string->symbol (string-append "dis" "play"))) "Hello world")

Good lord, as an example of why it's something we should want?

Each to their own of course, but..

I don't think this is the sort of code that people tend to write. But it does a good job of succinctly explaining how Tcl works.

For example because it's kind of homoiconic. Since everything is a string you can define your own control flow constructs for example...

If you define your own, say, repeat-until loop, can you use the built-in break and continue commands? Could you define a break-with-value command for the built-in loops?

Using Tcl exceptions, I guess it would be pretty trivial to do that.

Here [1] is an alternative do..while loop implementation provided by Tcllib, written in pure Tcl.

[1] https://core.tcl-lang.org/tcllib/artifact/4f7e97706ff67a40

Would it be fair to call this a kind of "pervasive eval"?

you've misspelled "evil" ;)

in TeX:

\def\a{mess}\def\b{age}\csname \a\b \endcsname {Hello there}\bye

in (UCB)LOGO:

? run list word "pri "nt [Hello there]

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