true. 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. 4. 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. All of Boole's algebra can be expressed in this calculus: We can test it with the classic "ex contradictione quodlibet" (ECQ) example "if p and not p, then q" for any q: So formally, q is true, whatever it is:) If this sounds overly theoretic, here's a tricky practical example in puzzle solving, Lewis Carroll's last sorites (pp. 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. I first don't understand why all premises can be just written in a row, which amounts to implicit "or", but it seems to work out well. 122 exercises to help you write better code. Every language has its own way of doing things. It was first created by John Osterhout in 1989. # This filter collects its input (should be finite;-) into a list: # $ streamlist {foo bar grill a} | sort | collect => a bar foo grill. We have Boolean operators in expr, so here goes: The only unary operator NOT can be written in terms of nand: .. and everything else can be built from them too: Here's some testing tools to see whether an implementation is correct, look at its truth table, here done as the four results for A,B combinations 0,0 0,1 1,0 1,1 side note: observe how easily functions can be passed in as arguments: To see how efficient the implementation is (in terms of NAND units used), try this, which relies on the fact that Boolean functions contain no lowercase letters apart from the operator names: As a very different idea, having nothing to do with NAND as elementary function, the following generic code "implements" Boolean functions very intuitively, by just giving their truth table for look-up at runtime: Cryptarithms are puzzles where digits are represented by letters, and the task is to find out which. $ mkdir ~/cs498gpl/exercises/tcl $ cd ~/cs498gpl/exercises/tcl. It includes a short introduction to TCP/IP, introductions on writing client-side scripts and GUI interfaces as well as integrating scripts with C/C++. 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. The absence of lexical scoping also led to constructs like sproc/reset, which stop a gap but aren't exactly elegant but Tcl's clear line between either local or global variables allows something like closures only by rewriting default arguments like done in remember (or like in Python). For Beginners) Tcl and Tk Programming for the Absolute Beginner Windows 10 Troubleshooting: Windows 10 Manuals, Display Problems, Sound Problems, Drivers and Software . The following code was created in the Tcl chatroom, instigated by the quote: "A computer is a state machine. The best part, its 100% free for everyone. }, Test data from http://csc.smsu.edu/~shade/333/project.txt. If both the operands are non-zero, then condition becomes true. As an example, here's a Stack class with push and pop methods, and an instance variable s a list that holds the stack's contents: The interp alias makes sure that calling the object's name, like. 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. After some head-scratching, I find it plausible, and possibly it is even the simplest possible solution, given the poorness of this RPN language. Bertrand Russell commented that the author "has revealed a new calculus, of great power and simplicity" (somehow sounds like Tcl;^). Note that on infinite streams, selectors may never return, e.g. If you use the tiny testing framework explained earlier, the e.g. The code below also serves as usage example: }. Exercise 1 - Tcl procedure. priority queue is any of the more clever ways: A*, Greedy, builds up a nest of foreachs suiting the problem, quick kills (with continue) to force unique values for the variables, and. Introduction to the Tcl 3 Language The next ve chapters constitute a Tcl language tutorial. The toplevel proc takes a paired list of inputs and expected output. In a very radical simplification, a whole world is built up by two operators, juxtaposition without visible symbol (which could be likened to or) and a overbar-hook (with the meaning of not) that I can't type here it's a horizontal stroke over zero or more operands, continued at right by a vertical stroke going down to the baseline. It aims at providing ability for programs to interact with other programs and also for acting as an embeddable interpreter. in the forum 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. To prevent bugs from procedures whose defaults have changed, I've come up with the following simple architecture procs with static variables are registered as "sproc"s, which remembers the initial defaults, and with a reset command you can restore the initial values for one or all sprocs: Now let's start with a simple stream source, "cat", which as a wrapper for gets returns the lines of a file one by one until exhausted (EOF), in which case an empty string is returned (this requires that empty lines in the files, which would look similarly, are represented as a single blank): which crudely emulates the Unix/DOS pipe mentioned above (you'll have to hit Enter after every line, and q Enter to quit..). For instance, we want all books printed before 1980: We might also store our patrons in the same database (here in a different style): Without a concept of "tables", we can now introduce structures like in relational databases. To find out how big a paper format is, one can measure an instance with a ruler, or look up appropriate documentation. Note that +/ is considered one operator, which applies the "adverb" folding to the "verb" addition (one might well call it "sum"). Rather, one could use read and write traces on variable M, causing it to load from, or store to, mem($HL). 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. Get better at programming through fun, rewarding coding exercises that test your understanding of concepts with Exercism. 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). which, when called with no arguments, return 1 or 0, respectively. 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. I only had to take care that when moving beyond its ends, I had to attach a space (written as _) on that end, and adjust the position pointer when at the beginning. 100% free, forever. In TOOT, the values of objects are represented as a list of length 3: the class name (so much for "runtime type information":-), a "|" as separator and indicator, and the values of the object, e.g. The other words (arguments) are not substituted because they're curly-braced, so either 0 or 1 is invoked, and does its simple job. Clif is the author of the TclTutor package2 and the books Tcl/Tk for Real Programmers and Tcl/Tk: A Developer's Guide3. # - rewrite a proc's default arg with given value. (I used uplevel instead of eval to keep all side effects in caller's scope). Deeper changes are possible with the unknown command, which is called if a command name is, well, unknown, and in the standard version tries to call executables, to auto-load scripts, or do other helpful things (see the file init.tcl). 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. For creating FORTRAN and the BNF style of language description, he received the ACM Turing Award in 1977. Our mentors will help you learn to think like a Tcl developer and how to write idiomatic code in Tcl. For easier handling, it's a good idea to classify records somehow (we'll want to store more than books), so we add. Different from switch, numbers are compared by numeric value, no matter whether given as decimal, octal or hex. Elements are not removed by the popping, but (if necessary) when re-pushing. The following scripts are plain Tcl, they don't use the Tk GUI toolkit (there's a separate chapter for those). ;-): 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. line-ends \r\n are not standardized to \n as usual in C), and prints as many lines as needed which each contain 16 bytes in hexadecimal notation, plus, where possible, the ASCII character. Implement an evaluator for a very simple subset of Forth. They are for instance the building blocks of relational databases and spreadsheets. The print version is available from Amazon in USA/Canada and their European sites including UK , Germany , France , Spain and Italy . For clearer code, it is advisable to factor out frequent operations into procs, e.g. Functions in Tcl are typically written with the proc command. Another example is this integer range generator (starts from 1, and is inclusive, so [iota1 5] == {1 2 3 4 5}): "NAND is not AND." The know command is called with a condition that should result in an integer when given to expr, and a body that will be executed if cond results in nonzero, returning the last result if not terminated with an explicit return. more is the most important "end-user" of streams, especially if they are infinite. The balance of longer programs can be computed by just adding the balances of their individual bytecodes: The partitioning will run for some seconds (depending on nmax I tried with several ten thousand), but it's needed only once. "Hello, World!" will get you writing some Tcl and familiarise yourself with the Exercism workflow. Tcl casts everything into the mold of a command, even programming constructs like variable assignment and procedure definition. 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. This video covers the basics that you need to start writing scripts with Tool Command Language (TCL or Tickle).Following topics are explained with simple exa. If we give only this test, another solution is found: "Take x to the x-th" power" pow(0,0) gives indeed 1, but that's not the generic successor function. ACM 21.8, Aug. 1978, 613-641), he developed an amazing framework for functional programming, from theoretical foundations to implementation hints, e.g. OK, I bite the bullet, set nmax to 500000, wait 5 minutes for the partitioning, and then: Hm.. cheap trick again it was discovered that the solution is just the successor of the second argument. Just like functions, procedures take arguments and return some value. 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. I started with Backus' first Functional Program example. Tcl's lists are well suited to represent sets. #-- This "functional form" is mostly called map in more recent FP: #-- Prefix multiplication comes as a special case of this: "if {\[$condition \$x\]} {$function \$x} else", #-- Testing, with K in another role as Konstant function:). 5. converting Java app to Tcl/Tk ( new thread for all the tcl/tk itcl gurus) 6. The idea in the paper I read is to use them as names of very simple functions: Glory be to the 11 rules of man Tcl that this is already a crude though sufficient reimplementation: The bracketed expr command is evaluated first, returning 0 or 1 as result of the comparison. See the examples soon to come. was instigated by the fact that in J, "NB." If they don't, we have found a fact that isn't dependent on the variable's value, and the resulting constant is returned, otherwise the unsolved expression: with a helper function in that reports containment of an element in a list: which means, in expr terms, {(!$a || $a) == 1}, for all values of a. 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. Tcl is used for web applications, desktop GUIs, testing and automation, and more. A collateral advantage is that all expressions are braced, without me having to care. The set of all defined bytecodes will be the alphabet of this little RPN language. in a priority queue, the object with the highest priority comes first. And three nested calls to vec are sufficient to produce the divisors list:). But if the database grows in size, it's a good idea to create indexes which cross-reference tags and values to IDs. These 20 syntax will definitely help you lot to start and improve your tcl scripting a lot. Here we can do what we want, even retrieve which fields we have used so far (using a temporary array to keep track of field names): Searching for records that meet a certain condition can be done sequentially. $ wish ex1proc.tcl. Clif first learned to program in high school in machine language on a Monroe 600 programmable . In this article, we will know how to use procedures in TCL. Develop fluency in 67 programming languages And when both x and !x exist, they are removed from the expression: translated back: "I avoid it, or it's not a kangaroo", or, reordered, " a" which by (4) means, "All kangaroos are avoided by me". Chapter 4 discusses Tcl I/O support for les, pipes, and sockets. I added converters between characters and integers, and between strings and lists (see the dictionary below). by one the binary operators +-*/. Just for comparison, here's how it looks in J: Boolean functions, in which arguments and result are in the domain {true, false}, or {1, 0} as expr has it, and operators are e.g. For example, in. On the other hand, Tk is a cross platform widget toolkit used for building GUI in many languages. All bits are initialized to 0. So [or] == 0 and [and] == 1. On the limits: Tcl arrays may get quite large (one app was reported to store 800000 keys in Greek characters), and at some point enumerating all keys with array names db (which produces one long list) may exceed your available memory, causing the process to swap. The book includes a short introduction to TCP/IP, as well as longer introductions to writing client . 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. After version 8.0/8.0, the unusually fast development of Tcl/Tk has slowed to a more normal pace. Here I use a global array for recording results: delivers in hardly noticeable time the R. numbers 1729, 4104, 13832 Or, how's this infinite Fibonacchi number generator, which on more fibo produces all the F.numbers (0,1,1,2,3,5,8,13,21) you might want? Also, memory limits on modern computers are somewhere up high so only at some time in the future you might have (but maybe not want) to change to a complex database;-). So, on a morning dogwalk, I thought out this strategy: Here's this version. Tcl supports multiple programming paradigms, including object-oriented . It just remains to check whether it does what we want. Maybe another weekend John Backus turned 80 these days. 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. 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 If bitval is given, sets the bit at numeric position position to 1 if bitval != 0, else to 0; in any case returns the bit value at specified position. . 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). This way, a stream can promise to be a potentially endless source of data, while taking only finite time to process and deliver what's really wanted. Without proof, I just claim that every function of n arguments whose characteristic integer is 2^(2^n) 1 is a tautology (or a true statement all bits are 1). For this we need to implement the construction operator, which is sort of inverse mapping while mapping a function over a sequence of inputs produces a sequence of outputs of that function applied to each input, Backus' construction maps a sequence of functions over one input to produce a sequence of results of each function to that input, e.g. In Europe and elsewhere, the most widely used paper format is called A4. J's "from" operator { takes zero or more elements from a list, possibly repeatedly. 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.. Retrieving fields that may not physically exist needs a tolerant access function: In a classical database we have to define tables: which fields of what type and of which width. In the next step, I want to reimplement the "median" function, which for a sorted list returns the central element if its length is odd, or the mean of the two elements adjacent to the (virtual) center for even length. personal mentoring, Though slick at first sight, we actually have to type more. Tcl is a scripting language somewhat like Perl but extensible and clearer. A program without such extravaganzas is shorter and yet does the same job, so it will have been tested earlier anyway. That's all. For instance, here's a breathtakingly short J program to compute the mean of a list of numbers: Only implicitly present is a powerful function combinator called "fork".