Below is the list of pages for this tag.

Transforming recursion to iteration via coroutines

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This blog post is adapted from my book The Tcl Programming Language.

Many programming tasks are very simply expressed and implemented through recursive algorithms, traversing a tree data structure being just one example. The primary reason recursion simplifies implementation is that the state of the computation is implicitly maintained, freeing the programmer from the burden of explicitly tracking the computational state of the program. For example, in a recursive tree walking implementation, the "current location" in the tree is implicitly tracked.

However, there are situations where a recursive model does not fit the needs of an application. For example, the application may want to traverse a tree in iterative fashion, retrieving one node at a time, operating on it and then potentially doing some unrelated computation before retrieving the next node at some unknown point in the future.

Here is where coroutines can bridge the impendance mismatch, presenting an iterative interface to a naturally recursive algorithm.

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Exploring Tcl internals from script - Part II

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A previous blog post described the representation command and its use for introspecting Tcl's internal structures for storing data. I promised a follow-up post that talked about Tcl's compiled byte code and the disassemble command for inspecting it. Well, only two years later, here is that post as promised.

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Exploring Tcl internals from script - Part I

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Tcl has some commands that are undocumented because they are liable to change, or even be removed, at any time, even in a patch release. Nevertheless, these commands can be very useful in exploring and understanding the inner workings of Tcl and in some cases, dealing with issues related to performance or interaction with external systems like COM on Windows.

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Introduction to Tcl Database Connectivity

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Tcl 8.6 shipped with the Tcl Database Connectivity (TDBC) API for accessing disparate SQL database implementations in a standard manner. I happened to need it for the first time recently and collected my notes into an introductory article for the benefit of those who, like me, prefer to be spoon fed.

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Hotkeys on Demand

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There is no shortage of hotkey programs for Windows, many of them of high quality. And of course Windows itself allows you to define hotkeys. However, a hotkey program in Tcl is not only very simple to write, it offers the full flexibility and power of Tcl behind it. Meaning what exactly? Read on.

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Playing God on Windows

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There are times during software development when you want to run in interactive mode with maximum privileges on a system, be God as it were. One might think running as Administrator would do it but it doesn't. To be truly omnipotent on Windows, you have to run under the LocalSystem account[1]. It is easy enough with Tcl and this post shows you how. As a side bonus, it also describes how to inject processes into the interactive user's desktop to run under the user's account as well.

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How do I exec thee? Let me count the ways...

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One of the strengths of Tcl is the ease of integration with other software, whether they be COM components, libraries or even executable programs that are not designed for interaction with other programs. Here we look the facilities Tcl offers related to the last of these -- running external programs and optionally interacting with them using standard I/O mechanisms.

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