A '''minimal Tcl escaping style''' is a [code style] that eschews unnecessary
Tcl escaping syntax.

** Description **

In some languages such as [C], [Javascript], [Lisp], and [Python], double
quotes indicate a certain type of value: a string.  In Tcl all values are
already strings, so double quotes do not have that function.  Instead, they
[dodekalogue%|%provide an environment] in which whitespace characters are
ordinary characters rather than [word] delimiters. [dodekalogue%|%Braces] do
the same, but additionally inhibit the [dodekalogue%|%standard substitutions].
It's technically possible to use [dodekalogue%|%backslash substitution] to
accomplish the same thing that quotes or braces do, but in all non-trivial
cases this results in unreadable scripts. 

A lot of Tcl code that one encounters employs [Dodekalogue%|%double quotes]
even when not strictly necessary.  Sometimes this is done to make a text editor
highlight those values; other times to make Tcl seem more like [C] or a [Unix]
[shell].  Such usage can be confusing to the beginner who is trying to
understand the intended use of double quotes, braces, and 
[Dodekalogue%|%backslash substitution].  Furthermore, the use of these
characters can at times have a performance impact that the beginner may find
subtle and surprising.

The minimal Tcl escaping style presented on this page
results in Tcl code that only employs Tcl escape environments where semantically
necessary, resulting in code that naturally avoids the pitfalls of extraneous
escaping.

Here are the rules of the minimal escaping style:

   '''braces''' :   Don't use braces where no backslash substitutions are otherwise needed.

   '''quotes''' :   Don't use quotes where braces could be used. 


That's it.  If your code follows this style, you can avoid potential
performance issues like `"[[unintended [shimmering]]]"`, as well as whatever
miniscule performance improvement that comes from minimizing double quote
processing by the Tcl interpreter.  This minimal style also "scales" better as
one moves into more complex forms of Tcl scripting such as [code generation].
Best of all , beginners will be able to learn by reading your code when braces
and quotes are actually needed.  It also helps to disabuse them of that
all-to-common misunderstanding that braces mean "[list]".

For example, if a value contains whitespace and also
[http://wiki.tcl.tk/10259#pagetoc9713972a#pagetoc9713972a%|%substitutions],
quotes would be the way to go, since braces would over-escape the value,
preventing the substitutions from occurring.

[MS] dons his evil hat and remarks: in that case, ''really'' minimal style could be without quotes or braces, just backslash-escape the whitespaces! Of course, it depends on how you define ''minimal'' ...

[PYK] 2015-04-30: Except that braces and quotes were presumably introduced into
the language specifically to alleviate backslash pain.  This minimal escaping
style merely advocates using them only for their respective intended purposes.
Note that the minimal escaping style says nothing about backslash escaping,
which is always fair game!



** Discussion **

[EMJ] (2015-04-22) Re "Sometimes this is done..." near the beginning: it might be done to clarify the purpose of a string, or with an eye on a future change (and so is about program maintainability). And I just don't believe the "seem more like [C]" bit.

[PYK] 2015-04-30:  Anyone who thinks they can improve this page is free to dive
in and rewrite it wholesale as far as I'm concerned....

[EMJ] 2015-04-30: No they can't, you'll put their name on the rewrites and try to turn them into another bit of your own private but global edit war!

[PYK] 2015-04-30: I added your name to your comments because they were in discussion format, expressing a different opinion.  In that case, the speakers need to be labeled so the reader can understand that it's different people talking.  If you don't want to attribute yourself,  you could always defer to ''anonymous coward'' or something.  In any case, other readers already aren't going to understand what we're discussing here because the page has already taken on another form.  That's cool.  It'll just need some cleanup later.

[RS] 2015-05-13: Some exceptions:
   * semicolons must be quoted/braced if not used as statement separators: 

======
set x [split $y ";"]
======

   * small characters are better visible if redundantly quoted/braced: e.g. "."

[PYK] 2015-05-13: To conform to the minimal escaping style, that would either be
======
set x [split $y \;]
======

or

======
set x [split $y {;}]
======

The idea behind the minimal escaping style is specifically to not use braces
quotes or backslash for side purposes such as increasing visibility of
characters, appeasing syntax highlighters, or posing as another language.  To
be justified under the minimal escaping style, a brace, quote, or backslash
must have a programmatic effect.  Says me :)



** Examples **

======
#instead of
puts "Hello!"

#use
puts Hello!
======


======
#instead of 
puts "Hello World."

#use
puts {Hello, World.}
======

======
#instead of 
proc {x} { ... }

#use
proc x { ... }
======

** See also **

   * [A question of style]


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