In Tcl, the two ways of reading a file are a good example: The second construct may be less efficient, but is robust for gigabyte-sized files. 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. The "main routine" is a single line that dumps all files given on the command line: Sample output, the script applied to itself: Roman numerals are an additive (and partially subtractive) system with the following letter values: Here's some Tcl routines for dealing with Roman numerals. 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. More experiments to discover the hypot() function: Hm the 3 is duplicated, divided by itself (=1), which is added to 4. After version 8.0/8.0, the unusually fast development of Tcl/Tk has slowed to a more normal pace. If a field content contains spaces, it must be quoted or braced too: Sorting a table can be done with lsort -index, taking care that the header line stays on top: Removing a row (or contiguous sequence of rows) by numeric index is a job for lreplace: Simple printing of such a table, a row per line, is easy with. Here's my little take on toot in a nutshell. Newbie Tcl/Tk exercises. Before starting your programming, make sure you have one text editor in place and you have enough experience to write a computer program, save it in a file, build it, and finally execute it. (One might truncate the list at front if it gets too long). On the other hand, Tk is a cross platform widget toolkit used for building GUI in many languages. 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. 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}. Tcl/Tk for Programmers is an introduction to the high-level Tcl/Tk scripting language for experienced programmers with either Unix or Windows background. ;-): 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. 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. All the rest would be there. Tcl is a scripting language somewhat like Perl but extensible and clearer. Tcl is a scripting language somewhat like Perl but extensible and clearer. 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. 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.. So here is one model of a state machine in ten lines of code. Write a function to determine if a list is a sublist of another list. I started with Backus' first Functional Program example. The extending code what is prepended to the previous unknown body. 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. Execution starts at the first of the states. In his Turing Award lecture, Can Programming Be Liberated from the von Neumann Style? Example: An existence map of ZIP codes between 00000 and 99999 can be kept in a list of 3125 integers (where each element requires about 15 bytes overall), while implementing the map as an array would take 100000 * 42 bytes in worst case, but still more than a bit vector if the population isn't extremely sparse in that case, a list of 1-bit positions, retrieved with lsearch, might be more efficient in memory usage. Let's try to prove "Modus Barbara" "if a implies b and b implies c, then a implies c": With less abstract variable names, one might as well write, But this has been verified long ago, by Socrates' death:^). Indexes: As shown, we can retrieve all data by sequential searching over array names. A filter takes one or more streams, and possibly other arguments, and reacts like a stream too. 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? We still have the canonical truth values 0 and 1 as returned from expr with a comparison operator. which is shorter and simpler, but meddles more directly with the stack. 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). This simple example invokes expr if the "command" is digestible for it: Imagine the makers of Tcl had failed to provide the if command. 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. Getting more daring, let's try a distributive law: Daring more: what if we postulate the equivalence? It was first created by John Osterhout in 1989. After some head-scratching, I find it plausible, and possibly it is even the simplest possible solution, given the poorness of this RPN language. Intro to Tcl: Exercises #2 Exercises #2 Rewrite the change function (Exercise 1.3) to work for any set of coins (or notes) for any decimal currency. It aims at providing ability for programs to interact with other programs and also for acting as an embeddable interpreter. This is provided e.g. They're great practice and fun to do! If you are able to automate below few task, more then 50% of work (based on TCL) can be done easily. Conversely, postulating non-equivalence turns out to be false in all cases, hence a contradiction: So again, we have a little proving engine, and simpler than last time. TCL scripting is much sought after skill set for every VLSI engineer. The GOTO "jumping" instruction is considered harmful in programming for many years now, but still it might be interesting to experiment with. In addition, for all procs, even without docstring, you get the "signature" (proc name and arguments with defaults). 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. Indexes are useful for repeated information that is likely to be searched. To try this in Tcl, here's a truth table generator that I borrowed from a little proving engine, but without the lsort used there the order of cases delivered makes best sense when the first bit is least significant: }. But the program "dd" (which just duplicates the top of stack twice) has a stack balance of +2, and hence can never pass the example test. For instance, if you would like to simplify the for loop, for the typical simple cases so you can write instead. 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. Bertrand Russell commented that the author "has revealed a new calculus, of great power and simplicity" (somehow sounds like Tcl;^). Tcl/Tk 8.2.3 and Tcl/Tk 8.3.0 under windows. Here is a routine for querying or setting single bits in vectors, where bits are addressed by non-negative integers. The following "constructor" does that, plus it normalizes the signs, reduces to lowest terms, and returns just the integer n if d==1: Conversely, this "deconstructor" splits zero or more rational or integer strings into num and den variables, such that [ratsplit 1/3 a b] assigns 1 to a and 3 to b: Arithmetical helper functions can be wrapped with func if they only consist of one call of expr: Languages like Lisp and Python have the docstring feature, where a string in the beginning of a function can be retrieved for on-line (or printed) documentation. The book includes a short introduction to TCP/IP, as well as longer introductions to writing client . However, this is no fundamental problem consider that. Like in real life, test cases have to be carefully chosen. 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." Tcl is a general purpose multi-paradigm system programming language. 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. bit foo 32 will turn foo into a list of two integers, if it was only one before. The following script. Different from switch, numbers are compared by numeric value, no matter whether given as decimal, octal or hex. This page is not available in other languages. My oversimple implementation assumes that the operator is one that expr understands: which returns 28 just as Dr. Backus ordered (= 1*6 + 2*5 + 3*4). Let's change that "a" can have only two values, "" or <>, so we might try to solve the expression by assuming all possible values for a, and see if they differ. For functional composition, where, say for two functions f and g. again a proc is created that does the bracket nesting: Why Backus used Transpose on the input, wasn't first clear to me, but as he (like we Tclers) represents a matrix as a list of rows, which are again lists (also known as vectors), it later made much sense to me. In an RPN language, the example might look like this: which has the advantage that execution goes from left to right, but requires some stack awareness (and some swaps to set the stack right;^), Implementing Def, I took an easy route by just creating a proc that adds an argument and leaves it to the "functional" to do the right thing (with some quoting heaven:-) }. Learning Objectives The first two days of this course provide a . But we can also multiply out the 1s with the divisors from the i ndex vector: So 6 is divisible by 2 and 3; non-zero elements in (lrange $divisors 1 end-1) gives the "proper" divisors. Tcl 8.5 Network Programming (2010) , by Kocjan and Beltowski, is targeted towards building network-aware applications using Tcl and includes coverage of many Tcl libraries and extensions. The toplevel proc takes a paired list of inputs and expected output. Nth Prime Tcl's lists are well suited to represent sets. The coin values should be passed to change as a variable number of arguments which are the coin values in units (e.g., a quarter would be represented as 25) in any order. of Tcl. Here's a routine that returns the numeric indices of all set bits in a bit vector: Sieve of Erastothenes: The following procedure exercises the bit vector functions by letting bits represent integers, and unsetting all that are divisible. If both the operands are non-zero, then condition becomes true. Tcl/Tk 8.5 Programming Cookbook (2011) , by Bert Wheeler, provides over 100 recipes to effectively use Tcl/Tk 8.5. Of course, with growing databases we may reach memory limits: arrays need some extra storage for administration. Ramanujan numbers: The pairs generator can be used to find Ramanujan numbers, which can be represented as the sum of two integer cubes in more than one way. # now do something with db($key) - but see below! Tcl - Logical Operators. Mathematically put. The source files for Tcl programs are named with the extension ".tcl". 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. The following code was created in the Tcl chatroom, instigated by the quote: "A computer is a state machine. Rational numbers, a.k.a. The following "General Problem Solver" (for small values of General) uses heavy metaprogramming: it. When two operands occur together, the "hook" pattern is implied, which might in Tcl be written as: As KBK pointed out in the Tcl chatroom, the "hook" pattern corresponds to Schnfinkel/Curry's S combinator (see Hot Curry and Combinator Engine), while "fork" is called S' there. A very simple control structure (one might also call it a result dispatcher) is the K combinator, which is almost terribly simple: It can be used in all situations where you want to deliver a result that is not the last. But bare-bones has its advantages too: in order to see how a clockwork works, you'd better have all parts visible:). But it looks halfway like the real thing: you get sort of an assembly listing with symbol table, and can run it I'd hardly start writing an assembler in C, but in Tcl it's fun for a sunny Sunday afternoon }, The mov b,INCR part is an oversimplification. "Hello, World!" is the traditional first program for beginning programming in a new language or environment. Implication (if a then b, a -> b) can in expr be expressed as $a <= $b just note that the "arrow" seems to point the wrong way. for installation, user privileges, and system self-protection. But if the database grows in size, it's a good idea to create indexes which cross-reference tags and values to IDs. As an embeddable interpreter, user privileges, and possibly tcl programming exercises arguments, and like! Ability for programs to interact with other programs and also for acting as an embeddable interpreter arrays some. New language or environment addressed by non-negative integers small values of General ) uses heavy metaprogramming: it somewhat Perl! Paired list of two integers, if it was only one before was first by... To create indexes which cross-reference tags and values to IDs - but see below the fast! A cross platform widget toolkit used for building GUI in many languages possibly other arguments, possibly... 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In many languages consider that and reacts like a stream too of code 8.0/8.0, the unusually fast development Tcl/Tk. Expr with a comparison operator General ) uses heavy metaprogramming: it tcl chatroom, by!

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