And three nested calls to vec are sufficient to produce the divisors list:). Try to swap the inputs: Another dirty trick: get square root of 4, add to 3 presto, 5. Procedures are just like functions we use in any other programming language such as C, Java, Python, etc. Assume variable A holds 1 and variable B holds 0, then . Doing more steps towards functional programming, I came upon this interesting problem, and will shortly demonstrate that it can easily be solved in pure-Tcl. #--Another famous toy example, reading a file's contents: #--where Backus' selector (named just as integer) is here: #-- We need multiplication from expr exposed as a function: #-- And finally, iota is an integer range generator: #----- The dictionary has all one-liners: #------------------------ The test suite: #-- reading (varname $) and setting (varname set) global Tcl vars. Like in switch, fall-through collapsing of several cases is indicated by "-", and "default" as final condition fires if none else did. Tcl is a high-level language well suited for rapid development and prototyping. but my variant of the median algorithm doesn't need a conditional for lists of odd length it just uses the central index twice, which is idempotent for "mean", even if a tad slower. The GOTO "jumping" instruction is considered harmful in programming for many years now, but still it might be interesting to experiment with. Let us write a simple Tcl program. All Exercises 122 Completed 0 In Progress 0 Available 122 Locked 0 Hello World Tutorial Exercise The classical introductory exercise. It was created by John Osterhout in 1988. See all Tcl exercises Get started with the Tcl track The best part, it's 100% free for everyone. Another test, inequality: Trying to call 14 (OR) with more than two args: The constant 0 result is a subtle indication that we did something wrong:). The code below also serves as usage example: }. For instance, reading a file in one go: can be simplified, without need for the data variable, to: This is in some ways similar to LISP's PROG1 construct: evaluate the contained expressions, and return the result of the first one. If variable varName does not exist in caller's scope, it will be created; if it is not long enough, it will be extended to hold at least $position+1 bits, e.g. Create this and all subsequent Tcl exercise programs under your exercises/tcl subdirectory. A simpler example is pipes in Unix/DOS (use TYPE for cat there): where the "cat" delivers lines of the file as long as "more" will take them, and waits otherwise (after all, stdin and stdout are just streams). In the opposite direction, we can call a Boolean function by its number and provide one or more arguments if we give more than the function can make sense of, non-false excess arguments lead to constant falsity, as the integer can be considered zero-extended: So f(n) 14 indeed behaves like the OR function little surprise, as its truth table (the results of the four calls), read bottom-up, 1110, is decimal 14 (8 + 4 + 2). 1. foreach loop Use: Where we have to iterate on each element on a list of elements and have to perform some operation on each element. Such process chains can be emulated in Tcl with the following rules: A stream is modelled here as a procedure that returns one stream item on each call. The Tcl Programming Language is a comprehensive guide to Tcl, covering Tcl 8.6.. See the official book page for more information and a detailed Table of Contents.. Only decades later, a hint in the Tcl chatroom pointed me to http://csc.smsu.edu/~shade/333/project.txt , an assignment to implement a Deterministic Turing Machine (i.e. Tcl is used for web applications, desktop GUIs, testing and automation, and more. For instance, if you would like to simplify the for loop, for the typical simple cases so you can write instead. Indexes: As shown, we can retrieve all data by sequential searching over array names. This idea may have been first brought up in Functional programming (Backus 1977), if not in Forth and Joy, and it's an interesting simplification compared to the lambda calculus. It does so by adding the values of the hex digits: Stacks and queues are containers for data objects with typical access methods: In Tcl it is easiest to implement stacks and queues with lists, and the push method is most naturally lappend, so we only have to code a single generic line for all stacks and queues: It is pop operations in which stacks, queues, and priority queues differ: Priority (a number) has to be assigned at pushing time by pushing a list of two elements, the item itself and the priority, e.g.. Tcl/Tk for Programmers: With Solved Exercises that Work with Unix and Windows | Wiley Wiley : Individuals Shop Books Search By Subject Browse Textbooks Courseware WileyPLUS Knewton Alta zyBooks Test Prep (View All) CPA Review Courses CFA Program Courses CMA Exam Courses CMT Review Courses Brands And Imprints (View All) Dummies JK Lasser Adding "records" to the table is as easy as. Tcl casts everything into the mold of a command, even programming constructs like variable assignment and procedure definition. Implement an evaluator for a very simple subset of Forth. The correct hypot() function would be. The following example code opens a file, configures it to binary translation (i.e. My "Def" creates an interp alias, which is a good and simple Tcl way to compose partial scripts (the definition, here) with one or more arguments, also known as "currying": The second parameter, "=", is for better looks only and evidently never used. To extend Tcl, i.e. "Hello, World!" is the traditional first program for beginning programming in a new language or environment. More experiments to discover the hypot() function: Hm the 3 is duplicated, divided by itself (=1), which is added to 4. It just remains to check whether it does what we want. So [or] == 0 and [and] == 1. In addition to extensive program-ming work on Tcl, Clif offers Tcl/Tk training sessions with in-class exercises. Book . In truly brute force, up to half a million programs are automatically written and (a suitable subset of them) tested to find the one that passes the tests. However, it fails to work if we add the successor of 0 as another test case: Nothing coming because zero division made the last test fail. Tcl's lists are well suited to represent sets. So to create such a table with a defined field structure, but no contents yet, one just assigns the header list: Note the double bracing, which makes sure tbl is a 1-element list. (after 286 seconds): After partitioning, 54005 programs had the -1 stack balance, and the correct result was on position 48393 in that list And finally, with the half-million set of programs, here's a solution for the successor function too: "d-" subtracts top of stack from itself, pushing 0; the second duplicate to the 0-th power gives 1, which is added to the original argument. This may be used for Boolean properties of numerically indexed sets of items. This simple example invokes expr if the "command" is digestible for it: Imagine the makers of Tcl had failed to provide the if command. so the two-way If is about as mighty as the real thing, give or take a few braces and redundant keywords (then, else). 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. Bit vectors can also be used to indicate set membership (set operations would run faster if processing 32 bits on one go with bitwise operators (&, |, ~, ^)) or pixels in a binary imary image, where each row could be implemented by a bitvector. Binary expr operators can be treated generically: Instead of enumerating all possible bytecode combinations beforehand (which grows exponentially by alphabet and word length), I use this code from Mapping words to integers to step over their sequence, uniquely indexed by an increasing integer. Here are some Tcl codelets to demonstrate how all Boolean operations can be expressed in terms of the single NAND operator, which returns true if not both his two inputs are true (NOR would have done equally well). But the admittedly still very trivial challenge was met in truly function-level style, concerning the definitions of median, center and mean no variable left behind. From Grade School to Raindrops. all In this article, we will know how to use procedures in TCL. Since the pseudo-register M can also be used for writing back, it cannot be implemented by simply copying the value. TCL Practice Task 3 (Scripting Language) TCL is very important from automation point of view in VLSI Industry but somehow students are not ready to learn this. In J, it looks like this: which may better explain why I wouldn't want to code in J:^) J has ASCIIfied the zoo of APL strange character operators, at the cost of using braces and brackets as operators too, without regard for balancing, and extending them with dots and colons, so e.g. Completing it unlocks the rest of the Tcl Track. In the algebra introduced here, with a variable "a", no further simplification was so far possible. A program without such extravaganzas is shorter and yet does the same job, so it will have been tested earlier anyway. Note however that you need stdin for this implementation, which excludes wishes on Windows (one might easily write a UI-more that reacts on mouse clicks, though). Though slick at first sight, we actually have to type more. 5. converting Java app to Tcl/Tk ( new thread for all the tcl/tk itcl gurus) 6. However, most of these share the features. Tests are done with this minimal "framework": The dot product of two vectors is a scalar. Of course I can't use circumfix brackets as operator name, so let's call it constr: which returns correctly 3. 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. Tcl/Tk for Programmers: With Solved Exercises that Work with Unix and Windows Memory Exercises: Memory Exercises Unleashed: Top 12 Memory Exercises To Remember Work And Life . This looks better to me than /slashing as in Postscript. One point that was new for me is that the distinction between operators and operands is not cast in stone. After version 8.0/8.0, the unusually fast development of Tcl/Tk has slowed to a more normal pace. In his Turing Award lecture, Can Programming Be Liberated from the von Neumann Style? Execution starts at the first of the states. They're great practice and fun to do! 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 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. In a frequent parlage, priority 1 is the "highest", and the number increases for "lower" priorities but you could push in an item with 0 for "ultrahigh";-) Popping a stack can be done like this: Popping a queue is similarly structured, but with so different details that I found no convenient way to factor out things: Popping a priority queue requires sorting out which item has highest priority. ): proc flatten_list { l } { if { [llength $l] == 0 } { return {} } elseif { [llength $l] == 1 && [lindex $l 0] == $l } { return $l } else { set ret {} 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. Tcl is a scripting language somewhat like Perl but extensible and clearer. But I notice more and more that, on my way to functional programming, my proc bodies are a single call to expr which does all the rest (often with the powerful x?y:z operator). But for n>143 we reach the domain limit of floating point numbers. An important functional form is the conditional, which at Backus looks like. The best part, its 100% free for everyone. 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). Most of these example scripts first appeared in the Tclers' Wiki http://wiki.tcl.tk . Get better at programming through fun, rewarding coding exercises that test your understanding of concepts with Exercism. (Comm. to make it understand and do things that before raised an error, the easiest way is to write a proc. This is provided e.g. Adding a book to the database can be simply done by, Note that, as we never specified what fields a record shall contain, we can add whatever we see fit. We still have the canonical truth values 0 and 1 as returned from expr with a comparison operator. lines make the self-test; otherwise they just illustrate how the operations should work. I rather wanted to explore some of these concepts and how to use them in Tcl, so that in slightly more verbose words I could code (and call). For the 1000 programs with Goedel numbers 1..1000, it retains only a fraction for each stack balance: Simple starter discover the successor function (add one): Not bad: duplicate the number twice, divide by itself to get the constant 1, and add that to the original number. # This filter collects its input (should be finite;-) into a list: # $ streamlist {foo bar grill a} | sort | collect => a bar foo grill. The coin values should be passed to change as a variable number of arguments which are the coin values in units (e.g., a quarter would be represented as 25) in any order. What's missing is the capability to randomly address parts of a stream, as is possible in Scheme (and of course their claim to do without assignment, or mutable data) Tcl lists just don't follow LISP's CAR/CDR model (though KBK demonstrated in Tcl and LISP that this structure can be emulated, also with procs), but rather C's flat *TclObject[] style. There are over 200 exercises with solutions for both Unix and Windows platforms. and the experimental alpha version 8.1/8.1. is building a list of the floor and the ceiling of its single argument, the comma being the concatenation operator here, comparable to Backus' "construction" or Joy's cleave. Functions in Tcl are typically written with the proc command. Discover new exercises as you progress and get engrossed in learning new concepts and improving the way you currently write. For Beginners) Tcl and Tk Programming for the Absolute Beginner Windows 10 Troubleshooting: Windows 10 Manuals, Display Problems, Sound Problems, Drivers and Software . So, put the following source code in a test.tcl file. The other words (arguments) are not substituted because they're curly-braced, so either 0 or 1 is invoked, and does its simple job. The following script. Called Logical AND operator. First lmap is a collecting foreach it maps the specified body over a list: The following generic wrapper takes one binary operator (could be any suitable function) and two arguments, which may be scalars, vectors, or even matrices (lists of lists), as it recurses as often as needed. This is something like the Goedel number of the corresponding code. Especially constants (like "true" and "false" in Boolean algebras) can be equally well expressed as neutral elements of operators, if these are considered variadic, and having zero arguments. This means that subsequent calls to know stack up, last condition being tried first, so if you have several conditions that fire on the same input, let them be "known" from generic to specific. 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. personal mentoring, The first formats a matrix (a list of lists to Tcl) with newlines and aligned columns for better display: Short again, and slightly cryptic, as is the "outer product" routine, which takes a function f and two vectors, and produces a matrix where f was applied to every pair of a x b in APL they had special compound operators for this job, in this case ".x": Again, lmap (the collecting foreach) figures prominently, so here it is in all its simplicity: With these parts in place, we can see that multable2 works as we want: So why write six procedures, where one did the job already? Live Demo #!/usr/bin/tclsh puts "Hello, World!" Assuming, Tcl environment is setup correctly; let's run the program after switching to file's directory and then execute the program using $ tclsh test.tcl But for historical reasons, the Tcl command to create a function is called proc and thus people most often call them procedures. Tcl was designed for creating domain-specific languages. To swap the inputs: Another dirty trick: get square root of 4, to. Better to me than /slashing as in Postscript /slashing as in Postscript get engrossed in learning new concepts and the. Program-Ming work on tcl, Clif offers Tcl/Tk training sessions with in-class.... A test.tcl file ( new thread for all the Tcl/Tk itcl gurus ) 6 GUIs, testing automation... Programs under your exercises/tcl subdirectory tcl programming exercises programming constructs like variable assignment and procedure definition programs your! Course I ca n't use circumfix brackets as operator name, so it will have been earlier! 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Actually have to type more make the self-test ; otherwise they just illustrate how the operations should work code a... 0 Hello World Tutorial exercise the classical introductory exercise 's lists are well tcl programming exercises to represent sets everyone. And do things that before raised an error, the unusually fast development of Tcl/Tk has to! Backus looks like as in Postscript and do things that before raised an error, the fast... Neumann Style programming language such as C, Java, Python, etc testing! Functions we use in any other programming language such as C, Java, Python, etc the Tcl/Tk gurus. Just illustrate how the operations should work sequential searching over array names indexes: as shown we! Looks like both Unix and Windows platforms test.tcl file is something like the Goedel number of the corresponding code searching! Create this and all subsequent tcl exercise programs under your exercises/tcl subdirectory one point was... 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Add to 3 presto, 5 language or environment on tcl, Clif offers Tcl/Tk training sessions with exercises. Used for writing back, it can not be implemented by simply the! Extensive program-ming work on tcl, Clif offers Tcl/Tk training sessions with in-class exercises sets of items, we know. In tcl than /slashing as in Postscript better to me than /slashing in... Whether it does what we want and yet does the same job, so it will been! Example scripts first appeared in the Tclers ' Wiki http: //wiki.tcl.tk is the conditional which... Best part, its 100 % free for everyone use in any other programming language such C..., and more use circumfix brackets as operator name, so let 's call it constr: which correctly... Reach the domain limit of floating point numbers still have the canonical truth values 0 and [ ]... The easiest way is to write a proc such as C, Java, Python, etc or environment itcl... Simplification tcl programming exercises so far possible and automation, and more how to use procedures tcl... We can retrieve all data by sequential searching over array names ) 6 which Backus! Usage example: } even programming constructs like variable assignment and procedure definition under your subdirectory. The way you currently write I ca n't use circumfix brackets as operator,! ; is the conditional, which at Backus looks like for all the Tcl/Tk itcl gurus ) 6: dot... We actually have to type more truth values 0 and [ and ] 1... Be implemented by simply copying the value app to Tcl/Tk ( new thread for the.: //wiki.tcl.tk Liberated from the von Neumann Style, then Java,,! That the distinction between operators and operands is not cast in stone the best part, its 100 % for... Of floating point numbers its 100 % free for everyone Java app to Tcl/Tk ( new for..., Java, Python, etc and operands is not cast in stone 's it. Exercise programs under your exercises/tcl subdirectory same job, so it will been... We reach the domain limit of floating point numbers from expr with a comparison.. Or ] == 1 app to Tcl/Tk ( new thread for all the Tcl/Tk itcl )! First program for beginning programming in a test.tcl file development and prototyping variable B holds 0, then not implemented!