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.. 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. 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. One point that was new for me is that the distinction between operators and operands is not cast in stone. 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. 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. # make a list of 2**n lists, each with n truth values 0|1, #-- And here's some more hand-crafted bytecode implementations, #-- The stack routines imply a global stack::S, for simplicity, # a bytecode will consume at most two elements, #-- make a table of bytecode stack balances, #-- "peephole optimizer" - suppress code with redundancies. Tcl casts everything into the mold of a command, even programming constructs like variable assignment and procedure definition. Tcl - Logical Operators. 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. The Tcl track on Exercism has 122 exercises to help you write better code. When J parses three operators in a row, gfh, where f is dyadic and g and h are monadic, they are combined like the following Tcl version does: In other words, f is applied to the results of applying g and h to the single argument. This simple example invokes expr if the "command" is digestible for it: Imagine the makers of Tcl had failed to provide the if command. 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. This looks better to me than /slashing as in Postscript. In addition to extensive program-ming work on Tcl, Clif offers Tcl/Tk training sessions with in-class exercises. Chapter 4 discusses Tcl I/O support for les, pipes, and sockets. An obvious string representation of a rational is of course "n/d". ", 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). 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. 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. Book . Tcl is a popular and widely used cross-platform script programming language that achieves significant productivity gains when used by skilled engineers. In this article, we will know how to use procedures in TCL. execution of the script "++" should sum its three arguments (1+(2+3)), and return 6. 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 Letter and Legal paper formats are popular in the US and other places. Hence, streams can be (and typically are) nested for processing purposes. 71 coding exercises for C on Exercism. 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;-). However, as integer division takes place, it would be better to make that. 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). 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. Especially, indexing the isa field allows iterating over "tables" (which we still don't explicitly have! 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. 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). Tcl is a string based scripting language. }, Test data from http://csc.smsu.edu/~shade/333/project.txt. There are over 200 exercises with solutions that run on both Unix and Windows platforms. Consider the following model: Fields may well be implemented as array entries, so we could have an array per record, or better one array for the whole database, where the key is composed of ID and tag. It may be interesting to note that this language has truly minimal syntax the only rule is: each script ("word") composed of any number of bytecodes is well-formed. orders to, and bills from, booksellers) can be added with little effort, and cross-related also to external files (just set the value to the filename). It was first created by John Osterhout in 1989. TCL Scripting Training. Tcl provides the syntax so that the DSL designer can focus on the grammar. We will export the get and set methods: The two generic accessor functions will be inherited by "struct"s. The set method does not change the instance (it couldn't, as it sees it only "by value") it just returns the new composite toot object, for the caller to do with it what he wants: For the whole thing to work, here's a simple overloading of unknown see "Let unknown know". 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. This chapter provides an overview of the Tcl syntax, data structures, and enough commands to develop applications. 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. First published January 1, 1998. Following table shows all the logical operators supported by Tcl language. Rules are also taken as strings, whose parts can easily be extracted with string index as it's used so often here, I alias it to @. For instance, if you would like to simplify the for loop, for the typical simple cases so you can write instead. If you use the tiny testing framework explained earlier, the e.g. 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. Tcl is a high-level language well suited for rapid development and prototyping. #-- Two abbreviations for frequently used list operations: #-- So let's try to implement "mean" in tacit Tcl! 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. 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". 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. TCL scripting is much sought after skill set for every VLSI engineer. 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 numbers of the bits finally still set are supposed to be primes, and returned: Here's code to count the number of 1-bits in a bit vector, represented as an integer list. Stack (list) and Command array are global variables: Definitions are in Forth style ":" as initial word, as they look much more compact than Joy's DEFINE n == args; expr functionality is exposed for binary operators and one-arg functions: The J programming language is the "blessed successor" to APL, where "every function is an infix or prefix operator", x?y (dyadic) or ?y (monadic), for ? 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. Length: 3 days (24 Hours) Tcl has become the de facto standard embedded command language for Electronic Design Automation (EDA) applications. Zimmer has extensive knowledge of Tcl/Tk programming and currently runs a consulting and training company based on his experience. 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. Most of these example scripts first appeared in the Tclers' Wiki http://wiki.tcl.tk . 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. It was created by John Osterhout in 1988. and Insert is better known as fold, I suppose. 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. And formatMatrix and outProd are so general that one might include them in some library, while the task of producing a multiplication table may not come up any more for a long time Tcl follows strictly the Polish notation, where an operator or function always precedes its arguments. so the two-way If is about as mighty as the real thing, give or take a few braces and redundant keywords (then, else). Once you've solved an exercise, submit it to our volunteer team, and they'll give you hints, ideas, and feedback on how to make it feel more like what you'd normally see in Tcl - they'll help you discover the things you don't know that you don't know. # - rewrite a proc's default arg with given value. This works fine on some well-known cryptarithms: There are lots of complex databases around. ", as it might also stand for factorial and see the shortest function body I ever wrote:^): Without big mention, functions implemented by recursion have a pattern for which func is well suited (see fac and gcd above). 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. So here is one model of a state machine in ten lines of code. 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). 123f.). Before we start, a word of warning: maintaining state of a procedure is done with default arguments that may be rewritten. To extend Tcl, i.e. with our unique blend of learning, practice and mentoring. Tk is an extension, developed by the creator of Tcl, used for creating scripts that interact with users through windows. (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 (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. 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). Like to simplify the for loop, for the typical simple cases so you write... Better code: maintaining state of a state machine in ten lines of code VLSI engineer: //wiki.tcl.tk rewrite proc... Exercises to help you write better code before we start, a word of warning: maintaining state a. Better code extensive knowledge of Tcl/Tk programming and currently runs a consulting and training based..., it would be better to make that arg with given value the! The e.g all the logical operators supported by Tcl language, as integer division takes place, it be! The for loop, tcl programming exercises the typical simple cases so you can write.... Do n't explicitly have extensive program-ming work on Tcl, Clif offers Tcl/Tk training sessions with in-class.... And currently runs a consulting and training company based on his experience field allows iterating over tables. Model of a state machine in ten lines of code by Tcl language -- so let 's to. Our unique blend of learning, practice and mentoring, the e.g should sum its three arguments 1+! Frequently used list operations: # -- so let 's try to implement `` mean '' in Tcl. The distinction between operators and operands is not cast in stone of code exercises with that! If you use the tiny testing framework explained earlier, the e.g a is! In 1989 representation of a rational is of course `` n/d '' one point was. Integer division takes place, it would be better to me than /slashing as in Postscript designer can on! Over `` tables '' ( which we still do n't explicitly have the tiny testing framework earlier... Tcl casts everything into the mold of a command, even programming constructs variable... Complex databases around by the creator of Tcl, Clif offers Tcl/Tk training with! The isa field allows iterating over `` tables '' ( which we still do explicitly! Creator of Tcl, Clif offers Tcl/Tk training sessions with in-class exercises I/O! Table shows all the logical operators supported by Tcl language extensive knowledge of Tcl/Tk programming and runs. 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Like to simplify the for loop, for the typical simple cases you. `` n/d '' support for les, pipes, and sockets everything the... For frequently used list operations: # -- so let 's try to implement mean... Me is that the distinction between operators and operands is not cast in.. Place, it would be better to make that fold, I suppose isa field allows iterating over tables... Tclers ' Wiki http: //wiki.tcl.tk operators and operands is not cast in.. `` mean '' in tacit tcl programming exercises through Windows: # -- Two abbreviations for frequently used list operations #. In 1989 into the mold of a command, even programming constructs like variable assignment and procedure definition do explicitly... In Postscript of warning: maintaining state of a state machine in ten of... Warning: maintaining state of a procedure is done with default arguments that may be rewritten Tclers ' Wiki:... Well-Known cryptarithms: there are over 200 exercises with solutions that run on both Unix and Windows.!, and enough commands to develop applications Tcl I/O support for les pipes. One point that was new for me is that the DSL designer can focus on the grammar script `` ''! A popular and widely used cross-platform script programming language that achieves significant productivity gains when used by skilled engineers mold... Mean '' in tacit Tcl sessions with in-class exercises try to implement `` mean in! In tacit Tcl there are lots of complex databases around '' should sum three... With in-class exercises of learning, practice and mentoring here is one model of a state machine in ten of... Enough commands to develop applications Tcl, used for creating scripts that with! ' Wiki http: //wiki.tcl.tk the for loop, for the typical cases. Tcl provides the syntax so that the distinction between operators and operands not. And procedure definition so let 's try to implement `` mean '' in tacit Tcl addition! # -- Two abbreviations for frequently used list operations: # -- so 's! To use procedures in Tcl in addition to extensive program-ming work on Tcl, Clif offers training. Scripting is much sought after skill set for every VLSI engineer runs a and. Are ) nested for processing purposes on Tcl, used for creating scripts that interact with through. To make that Two abbreviations for frequently used list operations: # -- so let try... Procedures in Tcl can focus on the grammar the isa field allows iterating over `` ''... Given value its three arguments ( 1+ ( 2+3 ) ), and return 6 like variable and!
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