Chapters 5-8 introduce more commands and techniques and Tcl's lists are well suited to represent sets. The test suite at end should give many examples of what one can do in "r". true. The discoverer, Second Edition, determines the stack balance of the first text, and tests only those programs of the same partition: But now for the trying. The following code was created in the Tcl chatroom, instigated by the quote: "A computer is a state machine. 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. 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. 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. For recursive functions and other arithmetics, func makes better reading, by accepting expr language in the body: We'll use this to turn expr's infix operators into dyadic functions, plus the "slashdot" operator that makes division always return a real number, hence the dot: For "fold", this time I devised a recursive version: Tacit enough (one might have picked fancier names like +/ for "sum" and # as alias for llength), but in principle it is equivalent to the J version, and doesn't name a single argument. For this we again need a 1-based integer range generator: At this point, a number is prime if the sum of the latest vector is 2. 71 coding exercises for C on Exercism. 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. Deeper changes are possible with the unknown command, which is called if a command name is, well, unknown, and in the standard version tries to call executables, to auto-load scripts, or do other helpful things (see the file init.tcl). Testing: Here's a different way to do it la functional programming: The body is nice and short, but consists of all unfamiliar commands. 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. Tcl doesn't have this mechanism built-in (and it would be hard to do it exactly the same way, because everything is a string), but a similar mechanism can easily be adopted, and it doesn't look bad in comparison: If the docstring is written in comments at the top of a proc body, it is easy to parse it out. is used as comment indicator, both being well known Latin abbreviations: Again, the "->" argument is for eye-candy only but it feels better to me at least. # This simple but infinite stream source produces all positive integers: # This produces all (well, very many) powers of 2: # A filter that reads and displays a stream until user stops it: # Here is a sample usage with famous name: #. which uses the (less) famous function maker: # Usage example: more {grep this {cat streams.tcl}}. 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. Note that +/ is considered one operator, which applies the "adverb" folding to the "verb" addition (one might well call it "sum"). 122 exercises I added converters between characters and integers, and between strings and lists (see the dictionary below). So let's get the pieces together. (I might have called it fun as well it sure is.) ", 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). This way, they are "pure values" and can be passed e.g. 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. save it to a file for printing. 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. Classes in C++ started out as structs, so I take a minimal struct as example, with generic get and set methods. The print version is available from Amazon in USA/Canada and their European sites including UK , Germany , France , Spain and Italy . Though slick at first sight, we actually have to type more. 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 . 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. One point that was new for me is that the distinction between operators and operands is not cast in stone. Tcl is no different. 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". 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:^). through functions that take a table and return a table. }, Test data from http://csc.smsu.edu/~shade/333/project.txt. Ah, the joys of weekend Tcl'ing and belatedly, Happy Birthday, John! It was created by John Osterhout in 1988. 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. This chapter provides an overview of the Tcl syntax, data structures, and enough commands to develop applications. The book includes a short introduction to TCP/IP, as well as longer introductions to writing client . * Edit and save ex1proc.tcl using the dosum proc and accompanying Tcl/Tk code from Tcl Syntax (procedures) Run ex1proc.tcl. Tcl provides the syntax so that the DSL designer can focus on the grammar. But for n>143 we reach the domain limit of floating point numbers. Just for comparison, here's how it looks in J: Boolean functions, in which arguments and result are in the domain {true, false}, or {1, 0} as expr has it, and operators are e.g. Write a function to determine if a list is a sublist of another list. 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. So here is one model of a state machine in ten lines of code. Adding "records" to the table is as easy as. Join Exercisms Tcl Track for access to Here's my little take on toot in a nutshell. J's "from" operator { takes zero or more elements from a list, possibly repeatedly. 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. I'm far from having digested it all, but like so often, interesting reading prompts me to do Tcl experiments, especially on weekends. 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. Tcl is a powerful scripting language that runs under Unix, Linux, VMS, DOS/Windows, OS/2, and MacOS (at least). They think it's a programing (like software programing) and they are in VLSI Industry to do some hardware related job. 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. 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. 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. Continuous, active development since the early 1990's. 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. being any pre- or user-defined function). 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. 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. (A && B) is false. 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: }. The partitioning helps very much in reducing the number of candidates. See all Tcl exercises Get started with the Tcl track The best part, it's 100% free for everyone. Here's our recommended free books that'll help you master Tcl. # Here is another stream producer that returns elements from a list: # This one repeats its list endlessly, so better use it with 'more': # This is sugar for first-time assignment of static variables: # But for a simple constant stream source, just use [subst]: # more {subst 1};# will produce as many ones as you wish. Since the pseudo-register M can also be used for writing back, it cannot be implemented by simply copying the value. Before we start, a word of warning: maintaining state of a procedure is done with default arguments that may be rewritten. 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:-) }. As everything is a string, and to Tcl "a" is {a} is a , Joy's polymorphy has to be made explicit. TCL is string based scripting language and also a procedural language. 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. in state space searching, where the kind of container of the to-do list determines the strategy: Recent-use lists: A variation that can be used both in a stack or queue fashion is a list of values in order of their last use (which may come handy in an editor to display the last edited files, for instance). Tcl is string based scripting language and also a procedural language point numbers commands and techniques and Tcl lists! The table is as easy as should give many examples of what one can do in `` ''! In stone, John the dictionary below ) another list also be used for writing,. 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