"Tacit programming" (tacit: implied; indicated by necessary connotation though not expressed directly) is one of the styles possible in J, and means coding by combining functions, without reference to argument names. Assume variable A holds 1 and variable B holds 0, then . 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. 123f.). We still have the canonical truth values 0 and 1 as returned from expr with a comparison operator. Indexes are useful for repeated information that is likely to be searched. * Edit and save ex1proc.tcl using the dosum proc and accompanying Tcl/Tk code from Tcl Syntax (procedures) Run ex1proc.tcl. 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). The source code is compiled into bytecode, which is later interpreted by the Tcl interpreter. The pattern, is a kind of conditional in J, which could in Tcl be written. (!a || !b), but then again, these functions are equivalent. was instigated by the fact that in J, "NB." # now do something with db($key) - but see below! 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 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. Streams in general should not be written in brackets (then the Tcl parser would eagerly evaluate them before evaluating the command), but braced, and stream consumers eval the stream at their discretion. The extending code what is prepended to the previous unknown body. The partitioning helps very much in reducing the number of candidates. 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. 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). A program without such extravaganzas is shorter and yet does the same job, so it will have been tested earlier anyway. Tcl 8.5 has the {*} construct to undo one-level of list packing (discussed on the Confluence page). Here is a routine for querying or setting single bits in vectors, where bits are addressed by non-negative integers. I added converters between characters and integers, and between strings and lists (see the dictionary below). 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. Notice that so far we have only defined one short proc, all other operations were done with built-in Tcl commands only. Introduction to the Tcl 3 Language The next ve chapters constitute a Tcl language tutorial. Tcl/Tk for Programmers introduces high-level Tcl/Tk scripting language to experienced programmers with either Unix or Windows backgrounds. 122 exercises Exercism is fun, effective and (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. Tcl - Environment Setup . In fact, the float limit is at n>170, so an intermediate result in the Stirling formula must have busted at 144. 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..). 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. Tcl/Tk for Programmers is an introduction to the high-level Tcl/Tk scripting language for experienced programmers with either Unix or Windows background. 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). Tcl is a high-level language well suited for rapid development and prototyping. 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. 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. Tcl (pronounced "tickle" or as an initialism) is a high-level, general-purpose, interpreted, dynamic programming language.It was designed with the goal of being very simple but powerful. 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. 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. 1. #-- Highlight the head position on the tape. Continuous, active development since the early 1990's. Tcl is a general purpose multi-paradigm system programming language. In the algebra introduced here, with a variable "a", no further simplification was so far possible. Core Python Programming, chapter 5 exercises number 5-3, question on this exercise. Create this and all subsequent Tcl exercise programs under your exercises/tcl subdirectory. Runtime of bit vector accesses is constant, except when a vector has to be extended to much larger length. An obvious string representation of a rational is of course "n/d". 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". Since the pseudo-register M can also be used for writing back, it cannot be implemented by simply copying the value. Nth Prime $ wish ex1proc.tcl. 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. 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. TCL Scripting Training. The following "General Problem Solver" (for small values of General) uses heavy metaprogramming: it. Execution starts at the first of the states. Don't take this as a fundamental critique of Tcl, though its underlying model is far more simple and elegant than LISP's (what with "special forms", "reader macros"), and yet powerful enough to do just about everything possible which is sort of a mathematical thriller, if you will. So I tried with another a^2+b^2=c^2 set, and HEUREKA! 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. execution of the script "++" should sum its three arguments (1+(2+3)), and return 6. The process of creating a simple database consists only of setting an initial value for the ID: Let's consider a library application for an example. To find out how big a paper format is, one can measure an instance with a ruler, or look up appropriate documentation. Tcl (Tool Command Language) is a very powerful but easy to learn dynamic programming language, suitable for a very wide range of uses, including web and desktop applications, networking, administration, testing and many more. Hence, streams can be (and typically are) nested for processing purposes. here is an implementation that even returns a list of the results of each iteration: using this, a string reverse function can be had as a one-liner: Another example is the following range-aware switch variation. Tcl was developed initially for Unix. being any pre- or user-defined function). For example, in. Mathematically put. Tcl supports multiple programming paradigms, including object-oriented . The print version is available from Amazon in USA/Canada and their European sites including UK , Germany , France , Spain and Italy . 560 pages, Paperback. following Backus' FP language with the "Def" command. A Functional Style and Its Algebra of Programs. 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. In SICP chapter 3.5, streams are introduced as data structures characterized as "delayed lists", whose elements are produced and returned only on demand (deferred evaluation). Try to swap the inputs: Another dirty trick: get square root of 4, add to 3 presto, 5. 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:^). 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. There are over 200 exercises with solutions that run on both Unix and Windows platforms. Here's my little take on toot in a nutshell. 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. 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. But if the database grows in size, it's a good idea to create indexes which cross-reference tags and values to IDs. In addition to extensive program-ming work on Tcl, Clif offers Tcl/Tk training sessions with in-class exercises. 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. 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. 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). As everything is a string, and to Tcl "a" is {a} is a , Joy's polymorphy has to be made explicit. But bare-bones has its advantages too: in order to see how a clockwork works, you'd better have all parts visible:). Tcl/Tk for Programmers is an introduction to the high-level Tcl/Tk scripting language for experienced programmers with either Unix or Windows background. Like in switch, fall-through collapsing of several cases is indicated by "-", and "default" as final condition fires if none else did. ACM 21.8, Aug. 1978, 613-641), he developed an amazing framework for functional programming, from theoretical foundations to implementation hints, e.g. which is shorter and simpler, but meddles more directly with the stack. 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). Other streams may provide a finite but very large number of elements, which would be impractical to process in one go. Bertrand Russell commented that the author "has revealed a new calculus, of great power and simplicity" (somehow sounds like Tcl;^). Indexes: As shown, we can retrieve all data by sequential searching over array names. 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 book includes a short introduction to TCP/IP, as well as longer introductions to writing client . For this, we reformat the expression to a list of values of type x or !x, that is in turn dumped into a local array for existence checking. Tables are understood here as rectangular (matrix) arrangements of data in rows (one row per "item"/"record") and columns (one column per "field"/"element"). Tcl - Logical Operators. So 8 is the associated integer of a&&b, but not only of this we get the same integer for ! Let us write a simple Tcl program. 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. 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. They think it's a programing (like software programing) and they are in VLSI Industry to do some hardware related job. 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. 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. A nice table also has a header line, that specifies the field names. 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. More experiments to discover the hypot() function: Hm the 3 is duplicated, divided by itself (=1), which is added to 4. Tcl/Tk 8.2.3 and Tcl/Tk 8.3.0 under windows. 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. 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!) (in a fantasy OO style): which, I admit, reads definitely better. Discover new exercises as you progress and get engrossed in learning new concepts and improving the way you currently write. }. Rational numbers, a.k.a. Here's typical set operations. I'm far from having digested it all, but like so often, interesting reading prompts me to do Tcl experiments, especially on weekends. Tcl Scripting Basic Examples Introducing 4th Gen Intel Xeon Scalable Processors Introducing 4th Gen Intel Xeon Scalable Processors Introducing 4th Gen Intel Xeon Scalable Processors The browser version you are using is not recommended for this site. Tk is an extension, developed by the creator of Tcl, used for creating scripts that interact with users through windows. Tcl/Tk 8.5 Programming Cookbook (2011) , by Bert Wheeler, provides over 100 recipes to effectively use Tcl/Tk 8.5. The source files for Tcl programs are named with the extension ".tcl". Explore the Tcl exercises on Exercism Unlock more exercises as you progress. It just remains to check whether it does what we want. # That's it. Now we can write n(f), which, given a Boolean function of one or more arguments, returns its characteristic number, by iterating over all cases in the truth table, and setting a bit where appropriate: So the characteristic integer is not the same as the Goedel number of a function, which would encode the structure of operators used there. I started with Backus' first Functional Program example. The best part, its 100% free for everyone. 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. For this we need to introduce a short-term memory also in the filter: which, tested on a n-element stream, returns n-1 averages: Yet another challenge was to produce an infinite stream of pairs {i j} of positive integers, i <= j, ordered by their sum, so that more pairs produces consecutively. Discussed on the tape is the associated integer of a rational is of course `` n/d.... Confluence page ) other operations were done with built-in Tcl commands only we get the same integer for short!! b ), and between strings and lists ( see the below! Run ex1proc.tcl use Tcl/Tk 8.5 Programming Cookbook ( 2011 ), by Bert Wheeler, provides over recipes. 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