J's "from" operator { takes zero or more elements from a list, possibly repeatedly. (I might have called it fun as well it sure is.) 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. # That's it. with automatic analysis 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). #-- Two abbreviations for frequently used list operations: #-- So let's try to implement "mean" in tacit Tcl! What's missing is the capability to randomly address parts of a stream, as is possible in Scheme (and of course their claim to do without assignment, or mutable data) Tcl lists just don't follow LISP's CAR/CDR model (though KBK demonstrated in Tcl and LISP that this structure can be emulated, also with procs), but rather C's flat *TclObject[] style. #-- 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:). Here is a routine for querying or setting single bits in vectors, where bits are addressed by non-negative integers. 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 @. Here I want to explore how a database can be implemented in the Tcl spirit of simplicity, and how far that approach takes us. 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. 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;-). ACM 21.8, Aug. 1978, 613-641), he developed an amazing framework for functional programming, from theoretical foundations to implementation hints, e.g. Tcl/Tk 8.5 Programming Cookbook (2011) , by Bert Wheeler, provides over 100 recipes to effectively use Tcl/Tk 8.5. #--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. "Hello, World!" is the traditional first program for beginning programming in a new language or environment. The toplevel proc takes a paired list of inputs and expected output. fractions, can be thought of as pairs of integers {numerator denominator}, such that their "real" numerical value is numerator/denominator (and not in integer nor "double" division!). 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). Note however that you need stdin for this implementation, which excludes wishes on Windows (one might easily write a UI-more that reacts on mouse clicks, though). 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. 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. 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. was instigated by the fact that in J, "NB." Tcl is available for Linux, Windows, Mac OS X, as well as other platforms, as open-source software under BSD-like license, or as pre-built binaries. It just remains to check whether it does what we want. All Tcl files will have an extension, i.e., .tcl. (A && B) is false. All the rest would be there. 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. It aims at providing ability for programs to interact with other programs and also for acting as an embeddable interpreter. The task is to conclude something from the following premises: These are encoded to the following one-letter predicates: So the problem set can be restated, in Spencer-Brown's terms, as. As everything is a string, and to Tcl "a" is {a} is a , Joy's polymorphy has to be made explicit. This is provided e.g. Ah, the joys of weekend Tcl'ing and belatedly, Happy Birthday, John! As a second step, we create the If command that wraps the expr invocation: This again passes impromptu tests, and adds the feature that any non-zero value counts as true and returns 1 if we neglect the other syntactic options of if, especially the elseif chaining. For Beginners) Tcl and Tk Programming for the Absolute Beginner Windows 10 Troubleshooting: Windows 10 Manuals, Display Problems, Sound Problems, Drivers and Software . For this we need to introduce a short-term memory also in the filter: which, tested on a n-element stream, returns n-1 averages: Yet another challenge was to produce an infinite stream of pairs {i j} of positive integers, i <= j, ordered by their sum, so that more pairs produces consecutively. in the forum Procedures are just like functions we use in any other programming language such as C, Java, Python, etc. If you use the tiny testing framework explained earlier, the e.g. 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. However, as integer division takes place, it would be better to make that. But the admittedly still very trivial challenge was met in truly function-level style, concerning the definitions of median, center and mean no variable left behind. The correct hypot() function would be. The book includes a short introduction to TCP/IP, as well as longer introductions to writing client . Tcl 8.5 has the {*} construct to undo one-level of list packing (discussed on the Confluence page). For easier handling, it's a good idea to classify records somehow (we'll want to store more than books), so we add. in a priority queue, the object with the highest priority comes first. As we've seen that
x is true for any x, we can cancel out such tautologies. $ wish ex1proc.tcl. Tests are done with this minimal "framework": The dot product of two vectors is a scalar. #puts "$mem($pc)\tA:$::A B:$::B C:$::C D:$::D E:$::E Z:$::Z", #----------------- "machine opcodes" implemented as procs, ; idiomatic: get over the initial variable(s), ; load double registers H+L with the address INCR, ; load byte to register B from the address pointed to in HL, "$body \$x [string repeat \] [llength $args]]". Tcl - Environment Setup . Classes in C++ started out as structs, so I take a minimal struct as example, with generic get and set methods. following Backus' FP language with the "Def" command. priority queue is any of the more clever ways: A*, Greedy, builds up a nest of foreachs suiting the problem, quick kills (with continue) to force unique values for the variables, and. 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. From Grade School to Raindrops. 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". Maybe another weekend John Backus turned 80 these days. Clif first learned to program in high school in machine language on a Monroe 600 programmable . 13Solving cryptarithms 14Database experiments 14.1A simple array-based database 14.2Tables as lists of lists 15Programming Languages Laboratory 15.1GOTO: a little state machine 15.2Playing Assembler 15.3Functional programming (Backus 1977) 15.4Reusable functional components 15.5Modelling an RPN language 15.6Tacit programming 16Vector arithmetics 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. 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). Assume John Smith borrows "The Tempest". The following example code opens a file, configures it to binary translation (i.e. # 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. All Exercises 122 Completed 0 In Progress 0 Available 122 Locked 0 Hello World Tutorial Exercise The classical introductory exercise. Join Exercisms Tcl Track for access to After some head-scratching, I find it plausible, and possibly it is even the simplest possible solution, given the poorness of this RPN language. The "machine" itself takes a list of alternating labels and state code; if a state code does not end in a goto or break, the same state will be repeated as long as not left, with goto or break (implicit endless loop). One could edit that file (not recommended), or rename unknown to something else and provide one's own unknown handler, that falls through to the original proc if unsuccessful, as shown in Radical language modification. In these Tcl experiments, I use "" for "" and angle-brackets <> for the overbar-hook (with zero or more operands in between). 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. The partitioning helps very much in reducing the number of candidates. They can be more precise than any "float" or "double" numbers on computers, as those can't exactly represent any fractions whose denominator isn't a power of 2 consider 13 which can not at any precision be exactly represented as floating-point number to base 2, nor as decimal fraction (base 10), even if bignum. Rational numbers, a.k.a. The special item "" (the empty string) indicates that the stream is exhausted. In addition to extensive program-ming work on Tcl, Clif offers Tcl/Tk training sessions with in-class exercises. Tcl Scripting Basic Examples Introducing 4th Gen Intel Xeon Scalable Processors Introducing 4th Gen Intel Xeon Scalable Processors Introducing 4th Gen Intel Xeon Scalable Processors The browser version you are using is not recommended for this site. # 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}}. Learning Objectives The first two days of this course provide a . Tcl is a high-level language well suited for rapid development and prototyping. 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