which, when called with no arguments, return 1 or 0, respectively. save it to a file for printing. Say you want to make a multiplication table for an elementary school kid near you. 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. 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}. A matter of style and taste, in a way multable is 10 LOC and depends on nothing but Tcl, which is good; multable2 describes quite concisely what it does, and builds on a few other procs that are highly reusable. The other words (arguments) are not substituted because they're curly-braced, so either 0 or 1 is invoked, and does its simple job. 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. I first don't understand why all premises can be just written in a row, which amounts to implicit "or", but it seems to work out well. Learn and practice Tcl by completing 122 exercises that explore different concepts and ideas. This idea may have been first brought up in Functional programming (Backus 1977), if not in Forth and Joy, and it's an interesting simplification compared to the lambda calculus. I added converters between characters and integers, and between strings and lists (see the dictionary below). Sorting can be done when pushing, or when popping, and since our push is so nicely generic I prefer the second choice (as the number of pushs and pops should be about equal, it does not really matter). The following scripts are plain Tcl, they don't use the Tk GUI toolkit (there's a separate chapter for those). In addition to extensive program-ming work on Tcl, Clif offers Tcl/Tk training sessions with in-class exercises. Tcl - Environment Setup . A math book showed me the Stirling approximation to n! 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. For example, in. 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). Tcl is a string based scripting language. 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. line-ends \r\n are not standardized to \n as usual in C), and prints as many lines as needed which each contain 16 bytes in hexadecimal notation, plus, where possible, the ASCII character. Exercism is fun, effective and Nth Prime (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. Clif is the author of the TclTutor package2 and the books Tcl/Tk for Real Programmers and Tcl/Tk: A Developer's Guide3. Runtime of bit vector accesses is constant, except when a vector has to be extended to much larger length. 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. The source code is compiled into bytecode, which is later interpreted by the Tcl interpreter. Running a Tcl/Tk applet within a Tcl/Tk program. It includes a short introduction to TCP/IP, introductions on writing client-side scripts and GUI interfaces as well as integrating scripts with C/C++. and the experimental alpha version 8.1/8.1. J's "from" operator { takes zero or more elements from a list, possibly repeatedly. After version 8.0/8.0, the unusually fast development of Tcl/Tk has slowed to a more normal pace. Accessing fields in a table is more fun with the field names than the numeric indexes, which is made easy by the fact that the field names are in the first row: Here is how to filter a table by giving pairs of field name and glob-style expression in addition to the header line, all rows that satisfy at least one of those come through (you can force AND behavior by just nesting such calls): This filters (and, if wanted, rearranges) columns, sort of what is called a "view": In the following few chapters you'll see how easy it is to emulate or explore other programming languages with Tcl. The print version is available from Amazon in USA/Canada and their European sites including UK , Germany , France , Spain and Italy . 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. For Tcl, there have been several OO extensions/frameworks (incr Tcl, XOTcl, stooop, Snit to name a few) in different flavors, but none can be considered as standard followed by a majority of users. Another example, cooked up by myself this time, computes the average of a list. Newbie Tcl/Tk exercises. After some head-scratching, I find it plausible, and possibly it is even the simplest possible solution, given the poorness of this RPN language. Procedural, OO, functional; builtin event loop for network programming and asynchronous file I/O. 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). See all Tcl exercises Get started with the Tcl track The best part, it's 100% free for everyone. No con-/destructors are needed, in contrast to the heavierweight matrix in Tcllib. The source files for Tcl programs are named with the extension ".tcl". But func isn't limited to math functions (which, especially when recursive, come out nice), but for expr uses in testing predicates as well: Exposing expr binary arithmetic operators as Tcl commands goes quite easy too: For "-", we distinguish unary and binary form: Having the modulo operator exposed, gcd now looks nicer: For unary not I prefer that name to "! Saving also goes a good way to what is ceremonially called "committing" (you'll need write-locking for multi-user systems), while loading (without saving before) might be called a "one-level rollback", where you want to discard your latest changes. lines make the self-test; otherwise they just illustrate how the operations should work. Here I want to explore how a database can be implemented in the Tcl spirit of simplicity, and how far that approach takes us. 122 exercises to help you write better code. in the forum However, as integer division takes place, it would be better to make that. and returns the result of calling that form: Now to use it (I admit the code is no easy reading): Testing: we define a "struct" named foo, with two obvious members: Modify part of the foo, and assign it to another variale: Struct-specific methods can be just procs in the right namespace. It was created by John Osterhout in 1988. For instance, here's how to make an authors' index in four lines: gives us a books list of all authors matching the given glob pattern (we reuse Tcl's functionality, instead of reinventing it). 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). 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. 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. Just choose how to implement instance variables: The task of frameworks, be they written in Tcl or C, is just to hide away gorey details of the implementation in other words, sugar it:) On the other hand, one understands a clockwork best when it's outside the clock, and all parts are visible so to get a good understanding of OO, it might be most instructive to look at a simple implementation. This means that subsequent calls to know stack up, last condition being tried first, so if you have several conditions that fire on the same input, let them be "known" from generic to specific. Ah, the joys of weekend Tcl'ing and belatedly, Happy Birthday, John! 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. 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. 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. 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. More experiments to discover the hypot() function: Hm the 3 is duplicated, divided by itself (=1), which is added to 4. Tcl/Tk for Programmers introduces high-level Tcl/Tk scripting language to experienced programmers with either Unix or Windows backgrounds. 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!) 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. Tables are understood here as rectangular (matrix) arrangements of data in rows (one row per "item"/"record") and columns (one column per "field"/"element"). In Tcl, a sensible implementation for compact data storage would be as a list of lists. Notice that so far we have only defined one short proc, all other operations were done with built-in Tcl commands only. 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..). Though slick at first sight, we actually have to type more. 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. Try to swap the inputs: Another dirty trick: get square root of 4, add to 3 presto, 5. {&&, ||,! TCL is string based scripting language and also a procedural language. Exercise 1 - Tcl procedure. As you see below, many functionalities can be "implemented" by just using Tcl's list functions. Introduction to the Tcl 3 Language The next ve chapters constitute a Tcl language tutorial. 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. Live Demo #!/usr/bin/tclsh puts "Hello, World!" Assuming, Tcl environment is setup correctly; let's run the program after switching to file's directory and then execute the program using $ tclsh test.tcl It was then ported to Windows, DOS, OS/2, and Mac OSX. The partitioning helps very much in reducing the number of candidates. 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. of your code and Here single bracing is correct. 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). #-- Highlight the head position on the tape. 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. 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. 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:-) }. 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. An important functional form is the conditional, which at Backus looks like. Here's our recommended free books that'll help you master Tcl. Like in switch, fall-through collapsing of several cases is indicated by "-", and "default" as final condition fires if none else did. But bare-bones has its advantages too: in order to see how a clockwork works, you'd better have all parts visible:). Mathematically put. Tcl's lists are well suited to represent sets. 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 # This filter collects its input (should be finite;-) into a list: # $ streamlist {foo bar grill a} | sort | collect => a bar foo grill. The book includes a short introduction to TCP/IP, as well as longer introductions to writing client . 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. Single bytecodes are executed, only to measure their effect on the stack. For a real 8080, one would have to say. In the algebra introduced here, with a variable "a", no further simplification was so far possible. The language is commonly used for rapid prototyping, scripted applications, GUIs, and testing. They think it's a programing (like software programing) and they are in VLSI Industry to do some hardware related job. Get better at programming through fun, rewarding coding exercises that test your understanding of concepts with Exercism. Factorial (n!) Tcl was designed for creating domain-specific languages. 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). The best part, its 100% free for everyone. Bit vectors can also be used to indicate set membership (set operations would run faster if processing 32 bits on one go with bitwise operators (&, |, ~, ^)) or pixels in a binary imary image, where each row could be implemented by a bitvector. #-- Two abbreviations for frequently used list operations: #-- So let's try to implement "mean" in tacit Tcl! If a field content contains spaces, it must be quoted or braced too: Sorting a table can be done with lsort -index, taking care that the header line stays on top: Removing a row (or contiguous sequence of rows) by numeric index is a job for lreplace: Simple printing of such a table, a row per line, is easy with. (A && B) is false. 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. 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