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'''Temporary:''' Just so this is easy to find for now. [[Reports:Tasks not implemented in Tcl]] ==Tasks Unlikely to get Implemented== This is a short discussion of the tasks that are marked with the omit template. —[[User:Dkf|Dkf]] 09:14, 21 May 2009 (UTC)
; [[Parametric Polymorphism]] : Tcl doesn't have static typing, making this task ridiculously trivial/non-applicable. Note also that the task itself states that it only applies to languages with static typing. ; [[Constrained Genericity]] : This is a specialization of the Parametric Polymorphism task, so all comments there apply here too.
== Language features ==
Tcl uses a mixture of pass-by-value and pass-by-reference, and is very good at simulating pass-by-name too. The base language semantics are strictly pass-by-value; this was how everything was done up to Tcl 7.6, and when combined with the fact that it was also string based, it gave the language a (deserved) reputation for being slow. In Tcl 8.0 the language implementation was switched to pass-by-reference, with the entities being semantically immutable objects (the actual code is more nuanced than that, of course); that was a major part of why Tcl sped up with that version. The pass-by-name support is through the
[http://www.tcl.tk/man/tcl8.6/TclCmd/upvar.htm upvar] command, which allows the looking-up of a variable in one scope and aliasing it to another variable in the current scope. —[[User:Dkf|Dkf]] 10:16, 31 May 2009 (UTC)
I've selected these features:
:Tcl's used a bytecode engine (with occasional interpretation) since 8.0, i.e., 1996.
:: OK, we've been discussing compiling to native code for a while now, but we've not got the effort to make that viable across lots of platforms, and going to a common bytecode format like JVM, CIL or LLVM is awkward as they are much more low-level than Tcl; for example, Tcl's variables aren't just simple bits of memory but also have a lot of other things that can be attached off them. —[[User:Dkf|Donal Fellows]] 08:23, 6 August 2009 (UTC)
:We use dynamic typing in
:We say it's a
ducklist if it supports the operations of a ducklist.
:Our type checks are applied at runtime only. That's when they are enforced strictly.
:We always pass parameters by value. We simulate pass-by-reference by passing handles/names and pass-by-name with the help of
:The language, especially in a safe interpreter, has no unsafe operations at all.
;paradigms=Imperative, Object-oriented, Event-driven, Reflective, Concurrent
:Tcl supports all of these handily enough. With more detail/justification:
::The Thread extension is long-established.
::While [[Tk]] has always been event driven, Tcl has been since 7.5 or 7.6 when it gained the event loop from Tk.
::Tcl is definitely an imperative language.
::Tcl supports this through many extensions, and natively from 8.6.
::Tcl's had introspection for ages; it's vital for the language's self-tests.
We need to check whether these features are enough; if not, we should update the Language template... —[[User:Dkf|Donal Fellows]] 12:26, 1 June 2009 (UTC)
How to use?
What is the correct command to start the examples? I tried 'tclsh' or 'wish', like