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. 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. 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. in static variables (here implemented with the fancy remember proc) examples are intgen that delivers ever increasing integers, or gets $fp where the file pointer advances at each call, so potentially all lines of the file are returned over time. Here's our recommended free books that'll help you master Tcl. The partitioning helps very much in reducing the number of candidates. Running a Tcl/Tk applet within a Tcl/Tk program. Maybe another weekend John Backus turned 80 these days. The pattern, is a kind of conditional in J, which could in Tcl be written. 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. 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 casts everything into the mold of a command, even programming constructs like variable assignment and procedure definition. First published January 1, 1998. Here is a routine for querying or setting single bits in vectors, where bits are addressed by non-negative integers. 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. Introduction to the Tcl 3 Language The next ve chapters constitute a Tcl language tutorial. The ebook version (PDF format) is available from Gumroad .. 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. Filters may be characterized as "selectors" (who may return only part of their input, like "grep") and/or "appliers" who call a command on their input and return the result. #-- We can compute the modulo of a number by its index vector: #-- and turn all elements where the remainder is 0 to 1, else 0: #-- Hence, 7 is only divisible by 1 and itself, hence it is a prime. Just like functions, procedures take arguments and return some value. #-- Move tape Left or Right as specified in rule. 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). Tcl is used for web applications, desktop GUIs, testing and automation, and more. Of course this is no real assembler. 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. 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. Try to swap the inputs: Another dirty trick: get square root of 4, add to 3 presto, 5. Indexes: As shown, we can retrieve all data by sequential searching over array names. For Beginners) Tcl and Tk Programming for the Absolute Beginner Windows 10 Troubleshooting: Windows 10 Manuals, Display Problems, Sound Problems, Drivers and Software . Tcl is much similar to other unix shell languages like Bourne Shell (Sh), the C Shell (csh), the Korn Shell (sh), and Perl. In a nutshell, his FP system comprises. On the other hand, the present approach is pretty economic, since it does not use field widths (all strings are "shrink-wrapped"), and omits empty fields, while at the same time allowing to add whatever fields you wish. Here single bracing is correct. Here I want to explore how a database can be implemented in the Tcl spirit of simplicity, and how far that approach takes us. A further optimization could be to tally value strings, and replace the frequent ones with "@$id", where db(@$id) holds the value once, and only db'get has to be adapted to redirect the query. Let's change that "a" can have only two values, "" or <>, so we might try to solve the expression by assuming all possible values for a, and see if they differ. Example: An existence map of ZIP codes between 00000 and 99999 can be kept in a list of 3125 integers (where each element requires about 15 bytes overall), while implementing the map as an array would take 100000 * 42 bytes in worst case, but still more than a bit vector if the population isn't extremely sparse in that case, a list of 1-bit positions, retrieved with lsearch, might be more efficient in memory usage. They are for instance the building blocks of relational databases and spreadsheets. A more generic filter takes a condition and a stream, and on each call returns an element of the input stream where the condition holds if ever one comes along: Friends of syntactic sugar might prefer shell style: and guess what, we can have that in Tcl too (and not in Scheme!-), by writing a proc, that also resets all sprocs, with the fancy name "$" (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 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. Tcl was designed for creating domain-specific languages. Syntax: foreach var $Var_list { //operations for each $var } Example: 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. 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. The following scripts are plain Tcl, they don't use the Tk GUI toolkit (there's a separate chapter for those). by one the binary operators +-*/. 560 pages, Paperback. So an "assembler" program in this plaything will run even slower than in pure Tcl, and consume more memory while normally you associate speed and conciseness with "real" assembler code. 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. Tcl/Tk for Programmers is an introduction to the high-level Tcl/Tk scripting language for experienced programmers with either Unix or Windows background. which is shorter and simpler, but meddles more directly with the stack. Our mentors will help you learn to think like a Tcl developer and how to write idiomatic code in Tcl. But if the database grows in size, it's a good idea to create indexes which cross-reference tags and values to IDs. "Hello, World!" is the traditional first program for beginning programming in a new language or environment. 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 shell application that reads TCL command from its standard input or from a file and gives desired results. $ mkdir ~/cs498gpl/exercises/tcl $ cd ~/cs498gpl/exercises/tcl. 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. For easier handling, it's a good idea to classify records somehow (we'll want to store more than books), so we add. 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: }. 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. In fact, the float limit is at n>170, so an intermediate result in the Stirling formula must have busted at 144. Grade School Given students' names along with the grade that they are in, create a roster for the school. ", http://csc.smsu.edu/~shade/333/project.txt, https://en.wikibooks.org/w/index.php?title=Tcl_Programming/Examples&oldid=3678753, Common Lisp: (documentation 'foo 'function), The ratio between the longer and the shorter side of an A format is constant, pop: retrieve and remove one object from the container, in a stack, the most recently pushed object is retrieved and removed (last in first out, LIFO), in a (normal) queue, it is the least recently pushed object (first in first out, FIFO). See all Tcl exercises Get started with the Tcl track The best part, it's 100% free for everyone. One point that was new for me is that the distinction between operators and operands is not cast in stone. for installation, user privileges, and system self-protection. Classes in C++ started out as structs, so I take a minimal struct as example, with generic get and set methods. It was created by John Osterhout in 1988. (I used uplevel instead of eval to keep all side effects in caller's scope). So I tried with another a^2+b^2=c^2 set, and HEUREKA! However, as integer division takes place, it would be better to make that. 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. bit foo 32 will turn foo into a list of two integers, if it was only one before. 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:). Assume variable A holds 1 and variable B holds 0, then . 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. These 20 syntax will definitely help you lot to start and improve your tcl scripting a lot. This is something like the Goedel number of the corresponding code. 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