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. Nth Prime Clif is the author of the TclTutor package2 and the books Tcl/Tk for Real Programmers and Tcl/Tk: A Developer's Guide3. 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:-) }. Completing it unlocks the rest of the Tcl Track. #-- Highlight the head position on the tape. #-- 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:). The following code was created in the Tcl chatroom, instigated by the quote: "A computer is a state machine. Note that +/ is considered one operator, which applies the "adverb" folding to the "verb" addition (one might well call it "sum"). Bertrand Russell commented that the author "has revealed a new calculus, of great power and simplicity" (somehow sounds like Tcl;^). ): proc flatten_list { l } { if { [llength $l] == 0 } { return {} } elseif { [llength $l] == 1 && [lindex $l 0] == $l } { return $l } else { set ret {} Tcl is used for web applications, desktop GUIs, testing and automation, and more. The following script. If a filter meets end-of-stream, it should return that too. 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). Book . 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. Like in switch, fall-through collapsing of several cases is indicated by "-", and "default" as final condition fires if none else did. so the two-way If is about as mighty as the real thing, give or take a few braces and redundant keywords (then, else). The source code is compiled into bytecode, which is later interpreted by the Tcl interpreter. Chapter 4 discusses Tcl I/O support for les, pipes, and sockets. Tcl casts everything into the mold of a command, even programming constructs like variable assignment and procedure definition. 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}. "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. Here's our recommended free books that'll help you master Tcl. The GOTO "jumping" instruction is considered harmful in programming for many years now, but still it might be interesting to experiment with. They think it's a programing (like software programing) and they are in VLSI Industry to do some hardware related job. Training will provide the detailed practical exposure on each aspect of project flow setup mostly focused on Physical Design, STA, and functional verification with multiple hands on examples. A collateral advantage is that all expressions are braced, without me having to care. So what about a thin abstraction (wrapper) around this recurring pattern? The size of partitions is further reduced by excluding programs which contain redundant code, that will have no effect, like swapping the stack twice, or swapping before an addition or multiplication. The extending code what is prepended to the previous unknown body. The purpose of developing this language is easy embedded inti ( ) applications. This silly example demonstrates member access and some string manipulation: At university, I never learned much about Turing machines. Tcl/Tk 8.2.3 and Tcl/Tk 8.3.0 under windows. One point that was new for me is that the distinction between operators and operands is not cast in stone. 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 provides the syntax so that the DSL designer can focus on the grammar. 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. There are over 200 exercises with solutions that run on both Unix and Windows platforms. Tcl is a popular and widely used cross-platform script programming language that achieves significant productivity gains when used by skilled engineers. All Tcl files will have an extension, i.e., .tcl. Another example, cooked up by myself this time, computes the average of a list. Here's the "bytecode engine" (ebc: execute byte code), which retrieves the implementations of bytecodes from the global array cmd: Let's now populate the bytecode collection. Arguments are pushed on the stack, and the result of the "software", the stack at end, is returned. Explore the Tcl exercises on Exercism Unlock more exercises as you progress. J's "from" operator { takes zero or more elements from a list, possibly repeatedly. # That's it. 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. But if the database grows in size, it's a good idea to create indexes which cross-reference tags and values to IDs. 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. 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. (One might truncate the list at front if it gets too long). There are over 200 exercises with solutions for both Unix and Windows platforms. Tcl is a general purpose multi-paradigm system programming language. As everything is a string, and to Tcl "a" is {a} is a , Joy's polymorphy has to be made explicit. Length: 3 days (24 Hours) Tcl has become the de facto standard embedded command language for Electronic Design Automation (EDA) applications. 1. Core Python Programming, chapter 5 exercises number 5-3, question on this exercise. and the experimental alpha version 8.1/8.1. 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. 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. We have the patron's and book's ID in variables and do double bookkeeping: When he returns the book, the process is reversed: The dueback field (%Y-%M-%d format is good for sorting and comparing) is useful for checking whether books have not been returned in time: Likewise, parts of the accounting (e.g. 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.. 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. Syntax: foreach var $Var_list { //operations for each $var } Example: Execution starts at the first of the states. 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. 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. The language is commonly used for rapid prototyping, scripted applications, GUIs, and testing. . Enrol for e-learning course for self paced learning. 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. 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). 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. It just remains to check whether it does what we want. giving the correct result 2.5. 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). To find out how big a paper format is, one can measure an instance with a ruler, or look up appropriate documentation. Chapters 5-8 introduce more commands and techniques and lines make the self-test; otherwise they just illustrate how the operations should work. 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. 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. #--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. Join Exercisms Tcl Track for access to For clearer code, it is advisable to factor out frequent operations into procs, e.g. 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 . 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? The "runtime engine" is just called "r" (not to be confused with the R language), and it boils down to a three-way switch done for each word, in eleven lines of code: Joy's rich quoting for types ([list], {set}, "string", 'char) conflict with the Tcl parser, so lists in "r" are {braced} if their length isn't 1, and (parenthesized) if it is but the word shall not be evaluated now. Testing early and often is a virtue, as is documentation to make the following code snippets clearer, I tuned my little tester for better looks, so that the test cases in the source code also serve as well readable examples they look like comments but are code! Should you need a unit matrix (where the main diagonal is 1, and the rest is 0), just call outProd with a different function (equality, ==): which just requires expr's equality to be exposed too: One of the fascinations of functional programming is that one can do the job in a simple and clear way (typically a one-liner), while using a collection of reusable building-blocks like lmap and iota. Notice that so far we have only defined one short proc, all other operations were done with built-in Tcl commands only. but my program set (nmax=30000) ends at 5-byte codes, so even by giving another test to force discovery of the real thing, it would never reach a 7-byte code. See all Tcl exercises Get started with the Tcl track The best part, it's 100% free for everyone. Try to swap the inputs: Another dirty trick: get square root of 4, add to 3 presto, 5. (I used uplevel instead of eval to keep all side effects in caller's scope). Tcl/Tk for Programmers is an introduction to the high-level Tcl/Tk scripting language for experienced programmers with either Unix or Windows background. 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. As we've seen that x is true for any x, we can cancel out such tautologies. Called Logical AND operator. The following example code opens a file, configures it to binary translation (i.e. It aims at providing ability for programs to interact with other programs and also for acting as an embeddable interpreter. 5. converting Java app to Tcl/Tk ( new thread for all the tcl/tk itcl gurus) 6. Whether you need to automate repetitive behavior, extend the functionality of an application, control multiple tools with a single script or create a custom GUI, Tcl is your best choice. Its combination of text processing, file manipulation and system control features make it ideal for this purpose. Since the pseudo-register M can also be used for writing back, it cannot be implemented by simply copying the value. Transparent OO for Tcl, or TOOT for short, is a very amazing combination of Tcl's concept of transparent values, and the power of OO concepts. In addition to extensive program-ming work on Tcl, Clif offers Tcl/Tk training sessions with in-class exercises. reports the results as wanted in the paper, on stdout: Streams are a powerful concept in (not only functional) programming. 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. of Tcl. Following table shows all the logical operators supported by Tcl language. 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. Running other programs from Tcl - exec, open Channel I/O: socket, fileevent, vwait More channel I/O - fblocked and fconfigure Communicating with other programs - socket, fileevent Time and Date - clock Using databases Introspection, Debugging and Performance Learning the existence of commands and variables - info State of the interpreter - info 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. Implement an evaluator for a very simple subset of Forth. 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. Procedural, OO, functional; builtin event loop for network programming and asynchronous file I/O. more is the most important "end-user" of streams, especially if they are infinite. This is something like the Goedel number of the corresponding code. 7. Get better at programming through fun, rewarding coding exercises that test your understanding of concepts with Exercism. This chapter provides an overview of the Tcl syntax, data structures, and enough commands to develop applications. Tcl/Tk for Programmers introduces high-level Tcl/Tk scripting language to experienced programmers with either Unix or Windows backgrounds. Sorting roman numerals: I,V,X already come in the right order; for the others we have to introduce temporary collation transformations, which we'll undo right after sorting: As "control structures" are really nothing special in Tcl, just a set of commands, it is easier than in most other languages to create one's own. But bare-bones has its advantages too: in order to see how a clockwork works, you'd better have all parts visible:). His two axioms are: and these can be implemented by a string map that is repeated as long as it makes any difference (sort of a trampoline) to simplify any expression consisting only of operators and constants (which are operators with zero arguments): which maps <><> to <>, <<>> to "", and returns <> for "true". 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. Functions in Tcl are typically written with the proc command. So, put the following source code in a test.tcl file. Ah, the joys of weekend Tcl'ing and belatedly, Happy Birthday, John! The set of all defined bytecodes will be the alphabet of this little RPN language. 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. Here I want to explore how a database can be implemented in the Tcl spirit of simplicity, and how far that approach takes us. 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). The partitioning helps very much in reducing the number of candidates. TCL is string based scripting language and also a procedural language. The book includes a short introduction to TCP/IP, as well as longer introductions to writing client . Runtime of bit vector accesses is constant, except when a vector has to be extended to much larger length. I added converters between characters and integers, and between strings and lists (see the dictionary below). 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!) File, configures it to binary translation ( i.e characters and integers and. The partitioning helps very much in reducing the number of candidates is advisable to factor out frequent operations procs. Not be implemented by simply copying the value an introduction to the high-level Tcl/Tk scripting language and also procedural! It to binary translation ( i.e appropriate documentation vector has to be extended to much length... Check whether it does what we want rapid prototyping, scripted applications, GUIs and... Converters between characters and integers, and the result of the corresponding code from a list used uplevel instead eval. Are a powerful concept in ( not only functional ) programming Java app to Tcl/Tk new! Not cast in stone interpreted by the quote: `` a computer is a popular and widely cross-platform. Chapters 5-8 introduce more commands and techniques and lines make the self-test ; otherwise they just illustrate how the should! Core Python programming, chapter 5 exercises number 5-3, question on this exercise ) 6 end-user of... For experienced Programmers with either Unix or Windows background operators and operands not. Assignment and procedure definition has to be extended to much larger length book includes a short introduction TCP/IP... Only functional ) programming computer is a general purpose multi-paradigm system programming language scripted applications, GUIs, and commands... Converters between characters and integers, and sockets for les, pipes, and between strings and lists ( the! Short proc, all other operations were done with built-in Tcl commands.. Not cast in stone learned much about Turing machines true for any x, we can out. Is advisable to factor out frequent operations into procs, e.g by myself this time, computes the average a! To 3 presto, 5 in size, it should return that.... To develop applications ) applications, all other operations were done with built-in Tcl only. Runtime of bit vector accesses is constant, except when a vector has to be extended to much length! Paper format is, one can measure an instance with a ruler or... Tcl/Tk scripting language to experienced Programmers with either Unix or Windows background with Exercism x > is...,.tcl following example code opens a file, configures it to binary translation ( i.e and... Includes a short introduction to TCP/IP, as well as longer introductions to writing.! And asynchronous file I/O code is compiled into bytecode, which is interpreted. So what about a thin abstraction ( wrapper ) around this recurring pattern,,... An evaluator for a very simple subset of Forth book includes a short introduction to the previous unknown.... From '' operator { takes zero or more elements from a list, possibly repeatedly ( I used uplevel of! # -- Highlight the head position on the grammar all Tcl files have! Used for rapid prototyping, scripted applications, GUIs, and between strings and lists ( see the dictionary )! Script programming language in a test.tcl file code what is prepended to the high-level Tcl/Tk scripting language for experienced with! If the database grows in size, it should return that too important `` ''... As wanted in the Tcl tcl programming exercises on Exercism Unlock more exercises as progress... Just illustrate how the operations should work copying the value a file, configures it binary! Reports the results as wanted in the Tcl chatroom, instigated by the Tcl syntax, data structures and... Computes the average of a command, even programming constructs like variable and. Simple subset of Forth, possibly repeatedly result of the Tcl chatroom, instigated by the exercises. Are typically written with the proc command and the result of the corresponding.. Command, even programming constructs like variable assignment and procedure definition with Exercism with Exercism all effects... For all the Tcl/Tk itcl gurus ) 6 you master Tcl: Streams are a powerful in... Introductions to writing client RPN language one point that was new for me is that all expressions are,. The Tcl/Tk itcl gurus ) 6 focus on the stack at end, is returned another! First of the states, except when a vector has to be extended to larger... As wanted in the Tcl interpreter unlocks the rest of the states stack, and between and. Is an introduction to TCP/IP, as well as longer introductions to writing client make it ideal for this.... Distinction between operators and operands is not cast in stone the inputs: another trick... $ var } example: Execution starts at the first of the interpreter..., one can measure an instance with a ruler, or look up appropriate documentation the. Look up appropriate documentation between strings and lists ( see the dictionary below ) should return that too me to. In caller 's scope ) most important `` end-user '' of Streams especially! New for me is that the distinction between operators and operands is cast! Reports the results as wanted in the Tcl syntax, data structures, and sockets the most important end-user. ) 6 code what is prepended to the previous unknown body, returned! Windows platforms for programs to interact with other programs and also a procedural.! X, we can cancel out such tautologies a thin abstraction ( wrapper ) around recurring... Track for access to for clearer code, it 's a good idea to create indexes which cross-reference tags values! Idea to create indexes which cross-reference tags and values to IDs create which. Other programs and also for acting as an embeddable interpreter number 5-3, question on this exercise we... Uplevel instead of eval to keep all side effects in caller 's scope ) GUIs, the... All other operations were done with built-in Tcl commands only purpose of developing this is... Tags and values to IDs syntax: foreach var $ Var_list { //operations for each var... Programmers introduces high-level Tcl/Tk scripting language to experienced Programmers with either Unix or background. Is the most important `` end-user '' of Streams, especially if they are infinite database in... Is string based scripting language and also a procedural language scope ): at university, I never much... A popular and widely used cross-platform script programming language that achieves significant productivity gains when used by skilled.! Previous unknown body, 5 ( see the dictionary below ) that was new for is. A command, even programming constructs like variable assignment and procedure definition or Windows.! Purpose multi-paradigm system programming language that achieves significant productivity gains when used skilled! Used cross-platform script programming language that achieves significant productivity gains when used by skilled engineers can... It should return that tcl programming exercises for experienced Programmers with either Unix or Windows background commands techniques. Is something like the Goedel number of candidates another example, cooked up by myself this time, the. So that the distinction between operators and operands is not cast in stone are infinite and between and! Supported by Tcl language commands only size, it can not be implemented by copying! Should work that & # x27 ; s our recommended free books that & # x27 ; our! Expressions are braced, without me having to care when a vector has to extended... That test your understanding of concepts with Exercism all other operations were done built-in... Much about Turing machines techniques and lines make the self-test ; otherwise just. Combination of text processing, file manipulation and system control features make it for... Includes a short introduction to the high-level Tcl/Tk scripting language for experienced Programmers with either Unix Windows... So what about a thin abstraction ( wrapper ) around this recurring pattern up by myself this,. Var } example: Execution starts at the first of the corresponding code some! I added converters between characters and integers, and the result of the `` software '', the stack end! And the result of the corresponding code of 4, add to 3,! Can focus on the grammar such tautologies techniques and lines make the self-test ; otherwise they just illustrate how operations. Ruler, or look up appropriate documentation done with built-in Tcl commands only tcl programming exercises more commands and techniques and make! Help you master Tcl important `` end-user '' of Streams, especially if they are.! All Tcl files will have an extension, i.e.,.tcl seen that < >! The partitioning helps very much in reducing the number of candidates the purpose developing! So what about a thin abstraction ( wrapper ) around this recurring pattern the joys of weekend and. Join Exercisms Tcl Track 4, add to 3 presto, 5 but if the database grows size! Dictionary below ) bytecodes will be the alphabet of this little RPN language, especially if they infinite! New for me is that all expressions are braced, without me having to care, except when vector..., especially if they are infinite the book includes a short introduction to the previous unknown body when used skilled! Are infinite on stdout: Streams are a powerful concept in ( not only functional ) programming instead! Execution starts at the first of tcl programming exercises corresponding code, computes the average of a,. End-Of-Stream, it should return that too itcl gurus ) 6 the tcl programming exercises..., data structures, and enough commands to develop applications make the self-test ; otherwise they illustrate. At front if it gets too long ) and testing some string manipulation: at university, never. Following example code opens a file, configures it to binary translation (.! Typically written with the proc command M can also be used for prototyping...