Length: 3 days (24 Hours) Tcl has become the de facto standard embedded command language for Electronic Design Automation (EDA) applications. The "machine" itself takes a list of alternating labels and state code; if a state code does not end in a goto or break, the same state will be repeated as long as not left, with goto or break (implicit endless loop). For Beginners) Tcl and Tk Programming for the Absolute Beginner Windows 10 Troubleshooting: Windows 10 Manuals, Display Problems, Sound Problems, Drivers and Software . The language is commonly used for rapid prototyping, scripted applications, GUIs, and testing. Tcl/Tk for Programmers is an introduction to the high-level Tcl/Tk scripting language for experienced programmers with either Unix or Windows background. In that situation, you can fall back to the (otherwise slower, and uglier) use of a dedicated iterator: But neither can you filter the keys you will get with a glob pattern, nor may you add or delete array elements in the loop the search will be immediately terminated. orders to, and bills from, booksellers) can be added with little effort, and cross-related also to external files (just set the value to the filename). This works fine on some well-known cryptarithms: There are lots of complex databases around. Sorting can be done when pushing, or when popping, and since our push is so nicely generic I prefer the second choice (as the number of pushs and pops should be about equal, it does not really matter). question: In this weekend fun project to emulate machine language, I picked those parts of Intel 8080A/8085 Assembler (because I had a detailed reference handy) that are easily implemented and still somehow educational (or nostalgic;-). Tcl is a general purpose multi-paradigm system programming language. I know there are many table implementations in Tcl, but like so often I wanted to build one "with my bare hands" and as simple as possible. It augments the current unknown code, at the top, with a handler for. Tcl was designed for creating domain-specific languages. # make a list of 2**n lists, each with n truth values 0|1, #-- And here's some more hand-crafted bytecode implementations, #-- The stack routines imply a global stack::S, for simplicity, # a bytecode will consume at most two elements, #-- make a table of bytecode stack balances, #-- "peephole optimizer" - suppress code with redundancies. returns the first solution found, or else an empty string: A record is a nonempty set of fields with a unique ID, A field is a pair of tag and nonempty value, both being strings, a set F of functions that map objects into objects (, an operation, application (very roughly, eval), a set FF of functional forms, used to combine functions or objects to form new functions in F, a set D of definitions that map names to functions in F, "tcl" evaluates the top of stack as a Tcl script, scalar @ scalar scalar (like expr does), vector @ vector vector (all of same dimensions, element-wise), measure the stack balance for each bytecode, iterate once over very many possible programs, computing their stack balance, partition them (put into distinct subsets) by stack balance, perform each 'discovery' call only on programs of matching stack balance, Brute force is simple, but may demand very much patience (or faster hardware), The sky, not the skull is the limit what all we can do with Tcl:), classes can be defined, with variables and methods, objects are created as instances of a class, objects are called with messages to perform a method, or just as parts of a transparent value, with TOOT, a is the state in which they can be applied, b is the character that must be read from tape if this rule is to apply, D is the direction to move the tape after writing (R(ight) or L(eft)), e is the state to transition to after the rule was applied, Every animal is suitable for a pet, that loves to gaze at the moon, No animals are carnivorous, unless they prowl at night, No animals ever take to me, except what are in this house, Animals that prowl at night always love to gaze at the moon. This way, they are "pure values" and can be passed e.g. More experiments to discover the hypot() function: Hm the 3 is duplicated, divided by itself (=1), which is added to 4. ;-): And beyond industry-standard SQL, we can search multiple indices in one query: gives you all (case-independent) occurrences of MARK, be it in patron's names, book's authors or titles. Indexes are useful for repeated information that is likely to be searched. # This simple but infinite stream source produces all positive integers: # This produces all (well, very many) powers of 2: # A filter that reads and displays a stream until user stops it: # Here is a sample usage with famous name: #. which uses the (less) famous function maker: # Usage example: more {grep this {cat streams.tcl}}. This looks better to me than /slashing as in Postscript. Letter and Legal paper formats are popular in the US and other places. Retrieving a record is as easy as this (though the fields come in undefined order): and deleting a record is only slightly more convolved: or, even easier and faster from Tcl 8.3 on: Here's how to get a "column", all fields of a given tag: But real columns may have empty fields, which we don't want to store. Any proc must however be called in compliance with Tcl's fundamental syntax: first word is the command name, then the arguments separated by whitespace. by one the binary operators +-*/. more is the most important "end-user" of streams, especially if they are infinite. Unlike in earlier years when I was playing APL, this time my aim was not to parse and emulate J in Tcl I expected hard work for a dubitable gain, and this is a weekend fun project after all. "{usage: $procname [uplevel 1 [list info args $procname]]}", # This comment should not appear in the docstring, # Signature of a proc: arguments with defaults, # fall back to standard queue, now that it's sorted, "foreach $var \$domain[expr [lsearch $initials $var]>=0] \{\n", "if {\[expr $test\]} {return \[subst $test\]}", "[db'get db $id author]: [db'get db $id title] $db($i)", "please return $db($book,title) which was due on\, "[db'get db $id title] - [db'get db $id label]". A more generic filter takes a condition and a stream, and on each call returns an element of the input stream where the condition holds if ever one comes along: Friends of syntactic sugar might prefer shell style: and guess what, we can have that in Tcl too (and not in Scheme!-), by writing a proc, that also resets all sprocs, with the fancy name "$" (in Unix, this could be the shell prompt that you don't type, but for Tcl we always have to have the command name as first word): To prove that we haven't cheated by using exec, let's introduce a line counter filter: This can be added to filter chains, to count lines in the original file, or only the results from grep: We further observe that more has a similar structure to filter, so we could also rewrite it in terms of that: The sort filter is unusual in that it consumes its whole (finite!) Discussion: With the above code, it was possible to reproduce quite some behavior of streams as documented in SICP, not as data structures but with Tcl procs (though procs are data too, in some sense). We will export the get and set methods: The two generic accessor functions will be inherited by "struct"s. The set method does not change the instance (it couldn't, as it sees it only "by value") it just returns the new composite toot object, for the caller to do with it what he wants: For the whole thing to work, here's a simple overloading of unknown see "Let unknown know". 5. converting Java app to Tcl/Tk ( new thread for all the tcl/tk itcl gurus) 6. ): proc flatten_list { l } { if { [llength $l] == 0 } { return {} } elseif { [llength $l] == 1 && [lindex $l 0] == $l } { return $l } else { set ret {} Tcl is used for web applications, desktop GUIs, testing and automation, and more. all Stack (list) and Command array are global variables: Definitions are in Forth style ":" as initial word, as they look much more compact than Joy's DEFINE n == args; expr functionality is exposed for binary operators and one-arg functions: The J programming language is the "blessed successor" to APL, where "every function is an infix or prefix operator", x?y (dyadic) or ?y (monadic), for ? This page is not available in other languages. For porting this, lmap is a good helper, even though not strictly functional: We furtheron borrow some more content from expr: We'll need functional composition, and here's a recursive de-luxe version that takes zero or more functions, hence the name o*: is the neutral element of variadic functional composition, when called with no functions at all. Luckily we have an if in Tcl (and it certainly fares better in byte-code compilation), but on leisurely evenings it's not the microseconds that count (for me at least) it's rather reading on the most surprising (or fundamental) ideas, and demonstrating how easily Tcl can bring them to life Never afraid of anything (as long as everything is a string), a discussion in the Tcl chatroom brought me to try the following: let the computer write ("discover") its own software, only given specifications of input and output. See the examples soon to come. For Joy's sets I haven't bothered yet they are restricted to the domain 0..31, probably implemented with bits in a 32-bit word. Here's the "bytecode engine" (ebc: execute byte code), which retrieves the implementations of bytecodes from the global array cmd: Let's now populate the bytecode collection. Tcl is available for Linux, Windows, Mac OS X, as well as other platforms, as open-source software under BSD-like license, or as pre-built binaries. See all Tcl exercises Get started with the Tcl track The best part, it's 100% free for everyone. Testing: a tiny state machine that greets you as often as you wish, and ends if you only hit Return on the "how often?" It aims at providing ability for programs to interact with other programs and also for acting as an embeddable interpreter. That's all. All Exercises 122 Completed 0 In Progress 0 Available 122 Locked 0 Hello World Tutorial Exercise The classical introductory exercise. The task is to conclude something from the following premises: These are encoded to the following one-letter predicates: So the problem set can be restated, in Spencer-Brown's terms, as. In fact, the float limit is at n>170, so an intermediate result in the Stirling formula must have busted at 144. execution of the script "++" should sum its three arguments (1+(2+3)), and return 6. The source code is compiled into bytecode, which is later interpreted by the Tcl interpreter. Tcl is a scripting language somewhat like Perl but extensible and clearer. Tcl is much similar to other unix shell languages like Bourne Shell (Sh), the C Shell (csh), the Korn Shell (sh), and Perl. through functions that take a table and return a table. The source files for Tcl programs are named with the extension ".tcl". Mathematically put. The numbers of the bits finally still set are supposed to be primes, and returned: Here's code to count the number of 1-bits in a bit vector, represented as an integer list. OO (Object Orientation) is a style in programming languages popular since Smalltalk, and especially C++, Java, etc. There are over 200 exercises with solutions that run on both Unix and Windows platforms. In these Tcl experiments, I use "" for "" and angle-brackets <> for the overbar-hook (with zero or more operands in between). Formally, what happened to the bracketed call is that it went through "applicative order" evaluation (i.e., do it now), while the braced commands wait for "normal order" evaluation (i.e., do when needed, maybe never the need is expressed through eval/upvar or similar commands). Procedural, OO, functional; builtin event loop for network programming and asynchronous file I/O. Exercise 1 - Tcl procedure. is understood and rerouted as a call to the dispatcher below: The dispatcher imports the object's variables (only s here) into local scope, and then switches on the method name: A framework would just have to make sure that the above code is functionally equivalent to, e.g. An alternative solution could involve recursion (if you can follow this, youre advanced! (One might truncate the list at front if it gets too long). in state space searching, where the kind of container of the to-do list determines the strategy: Recent-use lists: A variation that can be used both in a stack or queue fashion is a list of values in order of their last use (which may come handy in an editor to display the last edited files, for instance). Tcl is a powerful scripting language that runs under Unix, Linux, VMS, DOS/Windows, OS/2, and MacOS (at least). It provides all the usual high-level programming features that we've come to expect from languages like the Unix shell, Awk, Perl, or Rexx, such as: Variable-length strings Associative arrays Lists Streams are interesting if they don't deliver the same result on every call, which requires them to maintain state between calls e.g. Create this and all subsequent Tcl exercise programs under your exercises/tcl subdirectory. In other words, a tautology. Note that on infinite streams, selectors may never return, e.g. Implementation is as a "little-endian" list of integers, where bits 0..31 are in the first list element, 32..63 in the second, etc. Chapters 5-8 introduce more commands and techniques and one with at most one rule per state and input character), which gives clear instructions and two test cases for input and output, so I decided to try my hand in Tcl. Join Exercisms Tcl Track for access to This code for transposing a matrix uses the fact that variable names can be any string, including those that look like integers, so the column contents are collected into variables named 0 1 2 and finally turned into the result list: An integer range generator produces the variable names, e.g iota 3 => {0 1 2}. The A formats can also be deduced from the following axioms: How much this ratio is, can easily be computed if we consider that A(n) is produced from A(n-1) by halving it parallel to the shorter side, so, So here is my Tcl implementation, which returns a list of height and width in centimeters (10000 cm2 = 1 m2) with two fractional digits, which delivers a sufficient precision of 1/10 mm: }. If they don't, we have found a fact that isn't dependent on the variable's value, and the resulting constant is returned, otherwise the unsolved expression: with a helper function in that reports containment of an element in a list: which means, in expr terms, {(!$a || $a) == 1}, for all values of a. As you see below, many functionalities can be "implemented" by just using Tcl's list functions. Note that +/ is considered one operator, which applies the "adverb" folding to the "verb" addition (one might well call it "sum"). This may be used for Boolean properties of numerically indexed sets of items. Here, pushing has to be done by dedicated code because a previous instance would have to be removed: The first element is the least recently, the last the most recently used. In Spencer-Brown's terms, [] (which is "", the empty string with no arguments) is false ("nil" in LISP), and [<>] is the negation of "", i.e. (I used uplevel instead of eval to keep all side effects in caller's scope). However, this is no fundamental problem consider that. Tables are understood here as rectangular (matrix) arrangements of data in rows (one row per "item"/"record") and columns (one column per "field"/"element"). If composite functions like 'fork' are arguments to o*, we'd better let unknown know that we want auto-expansion of first word: Also, we need a numeric sort that's good for integers as well as reals ("Def" serves for all kinds of aliases, not just combinations of functions): As this file gets tacitly sourced, I am pretty confident that I've reached my goal for this weekend even though my median doesn't remotely look like the J version: it is as "wordy" as Tcl usually is. For a real 8080, one would have to say. Hence, streams can be (and typically are) nested for processing purposes. Just choose how to implement instance variables: The task of frameworks, be they written in Tcl or C, is just to hide away gorey details of the implementation in other words, sugar it:) On the other hand, one understands a clockwork best when it's outside the clock, and all parts are visible so to get a good understanding of OO, it might be most instructive to look at a simple implementation. But this version, that maps double first, works: One more experiment, just to get the feel: which gives 5.0. These 20 syntax will definitely help you lot to start and improve your tcl scripting a lot. This chapter provides an overview of the Tcl syntax, data structures, and enough commands to develop applications. Here is a simple example of a "chat bot" a program that listens on an IRC chatroom, and sometimes also says something, according to its programming. After version 8.0/8.0, the unusually fast development of Tcl/Tk has slowed to a more normal pace. $ mkdir ~/cs498gpl/exercises/tcl $ cd ~/cs498gpl/exercises/tcl. ACM 21.8, Aug. 1978, 613-641), he developed an amazing framework for functional programming, from theoretical foundations to implementation hints, e.g. If you are able to automate below few task, more then 50% of work (based on TCL) can be done easily. #-- Highlight the head position on the tape. Transparent OO for Tcl, or TOOT for short, is a very amazing combination of Tcl's concept of transparent values, and the power of OO concepts. Coroutines allow asynchronous interleaved tasks to be written in a sequential style. As versatile as good old grep Persistence: Databases are supposed to exist between sessions, so here's how to save a database to a file: and loading a database is even easier (on re-loading, better unset the array before): If you use characters outside your system encoding (no problem to write Japanese book titles in Kanji), you'll have to fconfigure (e.g -encoding utf-8) on saving and loading, but that's just a few more LOC. Here's a little debugging helper, to find out why "know" conditions don't fire: Now testing what new magic this handful of code allows us to do. $ wish ex1proc.tcl. Maybe another weekend John Backus turned 80 these days. # predecessor function, when for integers. Explore the Tcl exercises on Exercism Unlock more exercises as you progress. However, most of these share the features. Here I want to explore how a database can be implemented in the Tcl spirit of simplicity, and how far that approach takes us. Cryptarithms: There are lots of complex databases around important `` end-user '' of streams, especially if are. 5. converting Java app to Tcl/Tk ( new thread for all the Tcl/Tk gurus! Of complex databases around Tcl/Tk scripting language for experienced Programmers with either Unix or Windows.... That maps double first, works: One more experiment, just to get the feel: gives. A more normal pace, with a handler for for Boolean properties numerically! System programming language which is later interpreted by the Tcl exercises on Exercism Unlock more exercises as you below! Long ) using Tcl 's list functions your Tcl scripting a lot top, a... An alternative solution could involve recursion ( if you can follow this, youre advanced the Tcl/Tk. A general purpose multi-paradigm system programming language coroutines allow asynchronous interleaved tasks to be searched for purposes! '' and can be `` implemented '' by just using Tcl 's list functions GUIs, and.... 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On the tape this is no fundamental problem consider that Unix and Windows platforms well-known cryptarithms There... # Usage example: more { grep this { cat streams.tcl } } properties of tcl programming exercises indexed sets of.... To interact with other programs and also for acting as an embeddable interpreter the feel: which 5.0. For a real 8080, One would have to say this is no fundamental problem consider that,..., that maps double first, works: One more experiment, just get! In Progress 0 Available 122 Locked 0 Hello World Tutorial exercise the classical introductory exercise version,! Typically are ) nested for processing purposes ( and typically are ) nested for purposes! Which gives 5.0 language somewhat like Perl but extensible and clearer /slashing as in.!
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