#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]]". # 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}}. Completing it unlocks the rest of the Tcl Track. * Edit and save ex1proc.tcl using the dosum proc and accompanying Tcl/Tk code from Tcl Syntax (procedures) Run ex1proc.tcl. Clif is the author of the TclTutor package2 and the books Tcl/Tk for Real Programmers and Tcl/Tk: A Developer's Guide3. 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..). 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;-). OO (Object Orientation) is a style in programming languages popular since Smalltalk, and especially C++, Java, etc. bit foo 32 will turn foo into a list of two integers, if it was only one before. 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. There are over 200 exercises with solutions that run on both Unix and Windows platforms. 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. Nth Prime After version 8.0/8.0, the unusually fast development of Tcl/Tk has slowed to a more normal pace. Another test, inequality: Trying to call 14 (OR) with more than two args: The constant 0 result is a subtle indication that we did something wrong:). 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. # That's it. The language is commonly used for rapid prototyping, scripted applications, GUIs, and testing. 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:^). 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). is a popular function with super-exponential growth. TCL Scripting Training. It tries in brute force all programs up to the specified maximum Goedel number and returns the first one that complies with all tests: But iterating over many words is still pretty slow, at least on my 200 MHz box, and many useless "programs" are tried. Get better at programming through fun, rewarding coding exercises that test your understanding of concepts with Exercism. Called Logical OR Operator. 100% free. Try to swap the inputs: Another dirty trick: get square root of 4, add to 3 presto, 5. Tcl is a scripting language somewhat like Perl but extensible and clearer. 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. 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. Discover new exercises as you progress and get engrossed in learning new concepts and improving the way you currently write. They are for instance the building blocks of relational databases and spreadsheets. Of course I can't use circumfix brackets as operator name, so let's call it constr: which returns correctly 3. A filter takes one or more streams, and possibly other arguments, and reacts like a stream too. reports the results as wanted in the paper, on stdout: Streams are a powerful concept in (not only functional) programming. For instance, if the test has two inputs and wants one output, the stack balance is -1 (one less out than in). I won't go into all details of the above code, just some: (<.,>.) 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. Adding a book to the database can be simply done by, Note that, as we never specified what fields a record shall contain, we can add whatever we see fit. I only had to take care that when moving beyond its ends, I had to attach a space (written as _) on that end, and adjust the position pointer when at the beginning. 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. But this version, that maps double first, works: One more experiment, just to get the feel: which gives 5.0. Easily done in a few lines of Tcl code: The code does not directly puts its results, but returns them as a string you might want to do other things with it, e.g. 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}. Rules in this little challenge are of the form a bcD e, where, Here's my naive implementation, which takes the tape just as the string it initially is. Another example is this integer range generator (starts from 1, and is inclusive, so [iota1 5] == {1 2 3 4 5}): "NAND is not AND." For instance, if you would like to simplify the for loop, for the typical simple cases so you can write instead. Testing: Here's a different way to do it la functional programming: The body is nice and short, but consists of all unfamiliar commands. So [or] == 0 and [and] == 1. in the forum 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. #-- Highlight the head position on the tape. 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. Tcl/Tk for Programmers is an introduction to the high-level Tcl/Tk scripting language for experienced programmers with either Unix or Windows background. ACM 21.8, Aug. 1978, 613-641), he developed an amazing framework for functional programming, from theoretical foundations to implementation hints, e.g. 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. #-- We need basic scalar operators from expr factored out: "length mismatch [llength $a]!= [llength $b]". The book includes a short introduction to TCP/IP, as well as longer introductions to writing client . Here are some Tcl codelets to demonstrate how all Boolean operations can be expressed in terms of the single NAND operator, which returns true if not both his two inputs are true (NOR would have done equally well). 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. Implication (if a then b, a -> b) can in expr be expressed as $a <= $b just note that the "arrow" seems to point the wrong way. The Tcl track on Exercism has In the algebra introduced here, with a variable "a", no further simplification was so far possible. However, this is no fundamental problem consider that. 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? with our unique blend of learning, practice and mentoring. 560 pages, Paperback. 1. But bare-bones has its advantages too: in order to see how a clockwork works, you'd better have all parts visible:). }. The test suite at end should give many examples of what one can do in "r". 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. If we give only this test, another solution is found: "Take x to the x-th" power" pow(0,0) gives indeed 1, but that's not the generic successor function. 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. A program without such extravaganzas is shorter and yet does the same job, so it will have been tested earlier anyway. For Beginners) Tcl and Tk Programming for the Absolute Beginner Windows 10 Troubleshooting: Windows 10 Manuals, Display Problems, Sound Problems, Drivers and Software . in a priority queue, the object with the highest priority comes first. Tcl/Tk for Programmers is an introduction to the high-level Tcl/Tk scripting language for experienced programmers with either Unix or Windows background. 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. 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. It provides all the usual high-level programming features that we've come to expect from languages like the Unix shell, Awk, Perl, or Rexx, such as: Variable-length strings Associative arrays Lists In both cond and body you may use the variable args that holds the problem command unknown was invoked with. 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. However, most of these share the features. On the other hand, the present approach is pretty economic, since it does not use field widths (all strings are "shrink-wrapped"), and omits empty fields, while at the same time allowing to add whatever fields you wish. In Spencer-Brown's terms, [] (which is "", the empty string with no arguments) is false ("nil" in LISP), and [<>] is the negation of "", i.e. The following "General Problem Solver" (for small values of General) uses heavy metaprogramming: it. Here single bracing is correct. "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. Maybe another weekend John Backus turned 80 these days. 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. It just remains to check whether it does what we want. so the two-way If is about as mighty as the real thing, give or take a few braces and redundant keywords (then, else). Syntax: foreach var $Var_list { //operations for each $var } Example: Streams are interesting if they don't deliver the same result on every call, which requires them to maintain state between calls e.g. So here is one model of a state machine in ten lines of code. 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. 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. In these Tcl experiments, I use "" for "" and angle-brackets <> for the overbar-hook (with zero or more operands in between). This result (0 or 1) is substituted for the first word of this command. They always return a result (even if it is the empty string ""), so to call them functions might be most appropriate. personal mentoring, Before starting your programming, make sure you have one text editor in place and you have enough experience to write a computer program, save it in a file, build it, and finally execute it. This can be plugged into a filter chain to see what's going on: # or, to get a stream of even numbers, starting from 0: "to recall is to call -- (1 || 1) == 1", "PONG [info hostname] [lindex [split $line] 1]", "Try http://wiki.tcl.tk/[lindex $args end]", "Why do [string map {I you my your your my you me} $args]? Tcl is no different. Getting more daring, let's try a distributive law: Daring more: what if we postulate the equivalence? The pattern, is a kind of conditional in J, which could in Tcl be written. All Tcl files will have an extension, i.e., .tcl. Book . Compared to an RPN language, hypot would be. Don't take this as a fundamental critique of Tcl, though its underlying model is far more simple and elegant than LISP's (what with "special forms", "reader macros"), and yet powerful enough to do just about everything possible which is sort of a mathematical thriller, if you will. Here's typical set operations. 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++. So what about a thin abstraction (wrapper) around this recurring pattern? ", 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). A math book showed me the Stirling approximation to n! but my variant of the median algorithm doesn't need a conditional for lists of odd length it just uses the central index twice, which is idempotent for "mean", even if a tad slower. 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. Clif first learned to program in high school in machine language on a Monroe 600 programmable . 1. foreach loop Use: Where we have to iterate on each element on a list of elements and have to perform some operation on each element. TCL is shell application that reads TCL command from its standard input or from a file and gives desired results. of your code and 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 . However, as integer division takes place, it would be better to make that. Also, memory limits on modern computers are somewhere up high so only at some time in the future you might have (but maybe not want) to change to a complex database;-). After some head-scratching, I find it plausible, and possibly it is even the simplest possible solution, given the poorness of this RPN language. 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. In this article, we will know how to use procedures in TCL. The following scripts are plain Tcl, they don't use the Tk GUI toolkit (there's a separate chapter for those). It is however easy to build an interpreter for a language in Reverse Polish Notation (RPN) like Forth, Postscript, or Joy, and experiment with it. # 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. As everything is a string, and to Tcl "a" is {a} is a , Joy's polymorphy has to be made explicit. The toplevel proc takes a paired list of inputs and expected output. Called Logical AND operator. 4. The coin values should be passed to change as a variable number of arguments which are the coin values in units (e.g., a quarter would be represented as 25) in any order. 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 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. Say you want to make a multiplication table for an elementary school kid near you. 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. 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. was instigated by the fact that in J, "NB." Rather, one could use read and write traces on variable M, causing it to load from, or store to, mem($HL). The goto command is defined "locally", and deleted after leaving the state machine it is not meaningfully used outside of it. All the rest would be there. Write a function to determine if a list is a sublist of another list. I'm far from having digested it all, but like so often, interesting reading prompts me to do Tcl experiments, especially on weekends. #-- a little tester reports the unexpected: #-- The test suite should silently pass when this file is sourced: # reports a proc's args and leading comments. 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. Tcl - Environment Setup . 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 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'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. 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. Tcl/Tk 8.2.3 and Tcl/Tk 8.3.0 under windows. #-- We can compute the modulo of a number by its index vector: #-- and turn all elements where the remainder is 0 to 1, else 0: #-- Hence, 7 is only divisible by 1 and itself, hence it is a prime. In Europe and elsewhere, the most widely used paper format is called A4. #-- Move tape Left or Right as specified in rule. 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. Of it wanted in the paper, on stdout: streams are a powerful concept in ( only... Is commonly used for rapid prototyping, scripted applications, GUIs, and testing especially C++,,... 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Getting more daring, let 's try a distributive law: daring more: if... With solutions that Run on both Unix and Windows platforms and save ex1proc.tcl using dosum! The high-level Tcl/Tk scripting language for experienced Programmers with either Unix or Windows background writing.... I ca n't use circumfix brackets as operator name, so let 's try a distributive law daring... Of two integers, if it was only one before a function to determine a... It includes a short introduction to TCP/IP, introductions on writing client-side scripts GUI... Programming through fun, rewarding coding exercises that test your understanding of concepts tcl programming exercises Exercism integer... A thin abstraction ( wrapper ) around this recurring pattern queue, Object! Results as wanted in the paper, on stdout: streams are a powerful in. More daring, let 's try a distributive law: daring more: what if we the! N'T go into all details of the Tcl Track integer division takes place, it would be is A4. Elementary school kid near you: what if we postulate the tcl programming exercises course I ca use. And get engrossed in learning new concepts and improving the way you currently write Solver '' ( for small of. Used paper format is called A4 approximation to n make that program in high school in language! Of learning, practice and mentoring widely used paper format is called A4 the approximation!