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. Zimmer has extensive knowledge of Tcl/Tk programming and currently runs a consulting and training company based on his experience. # - rewrite a proc's default arg with given value. 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. Here I want to explore how a database can be implemented in the Tcl spirit of simplicity, and how far that approach takes us. 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. They are however better reusable than the multable proc above. Factorial (n!) An important functional form is the conditional, which at Backus looks like. input, sorts it, and acts as a stream source on the output: Now for the example in SICP: find the second prime in the interval between 10000 and 1000000. Letter and Legal paper formats are popular in the US and other places. 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). 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. 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. 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. 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: }. Of course this is no real assembler. This is provided e.g. Task 1:- Input Output File Handling & Rearranging Data Step 1: Create a file and named it "file_input1.txt" (Content of "file_input1.txt" is given below - Remember, you have create file exactly same as given. Maybe another weekend John Backus turned 80 these days. Learning Objectives The first two days of this course provide a . Exercism is fun, effective and The special item "" (the empty string) indicates that the stream is exhausted. So to create such a table with a defined field structure, but no contents yet, one just assigns the header list: Note the double bracing, which makes sure tbl is a 1-element list. in a priority queue, the object with the highest priority comes first. And that is one, and not the worst, Tcl way of Tacit programming APL and J (see Tacit programming) have the feature that arithmetics can be done with vectors and arrays as well as scalar numbers, in the varieties (for any operator @): Here's experiments how to do this in Tcl. It augments the current unknown code, at the top, with a handler for. The other words (arguments) are not substituted because they're curly-braced, so either 0 or 1 is invoked, and does its simple job. 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. And three nested calls to vec are sufficient to produce the divisors list:). Note that with this mapping, all valid programs (bytecode sequences) correspond to one unique non-negative integer, and longer programs have higher integers associated: Now out for discovery! In the algebra introduced here, with a variable "a", no further simplification was so far possible. Tcl/Tk 8.2.3 and Tcl/Tk 8.3.0 under windows. A math book showed me the Stirling approximation to n! Assume John Smith borrows "The Tempest". Rather, one could use read and write traces on variable M, causing it to load from, or store to, mem($HL). I won't go into all details of the above code, just some: (<.,>.) # now do something with db($key) - but see below! TCL Practice Task 3 (Scripting Language) TCL is very important from automation point of view in VLSI Industry but somehow students are not ready to learn this. #-- membership information is kept in an alias: #puts rule:$rule,tape:$tape,pos:$pos,char:$char. In that situation, you can fall back to the (otherwise slower, and uglier) use of a dedicated iterator: But neither can you filter the keys you will get with a glob pattern, nor may you add or delete array elements in the loop the search will be immediately terminated. A more generic filter takes a condition and a stream, and on each call returns an element of the input stream where the condition holds if ever one comes along: Friends of syntactic sugar might prefer shell style: and guess what, we can have that in Tcl too (and not in Scheme!-), by writing a proc, that also resets all sprocs, with the fancy name "$" (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!) For instance, reading a file in one go: can be simplified, without need for the data variable, to: This is in some ways similar to LISP's PROG1 construct: evaluate the contained expressions, and return the result of the first one. Whether you need to automate repetitive behavior, extend the functionality of an application, control multiple tools with a single script or create a custom GUI, Tcl is your best choice. Tcl supports multiple programming paradigms, including object-oriented . The entire syntax of Tcl is described in just 12 rules. So here is one model of a state machine in ten lines of code. Procedures are just like functions we use in any other programming language such as C, Java, Python, etc. The first formats a matrix (a list of lists to Tcl) with newlines and aligned columns for better display: Short again, and slightly cryptic, as is the "outer product" routine, which takes a function f and two vectors, and produces a matrix where f was applied to every pair of a x b in APL they had special compound operators for this job, in this case ".x": Again, lmap (the collecting foreach) figures prominently, so here it is in all its simplicity: With these parts in place, we can see that multable2 works as we want: So why write six procedures, where one did the job already? All Tcl files will have an extension, i.e., .tcl. #--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. 100% free. However, it fails to work if we add the successor of 0 as another test case: Nothing coming because zero division made the last test fail. # That's it. 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. Clif first learned to program in high school in machine language on a Monroe 600 programmable . bit foo 32 will turn foo into a list of two integers, if it was only one before. Example: An existence map of ZIP codes between 00000 and 99999 can be kept in a list of 3125 integers (where each element requires about 15 bytes overall), while implementing the map as an array would take 100000 * 42 bytes in worst case, but still more than a bit vector if the population isn't extremely sparse in that case, a list of 1-bit positions, retrieved with lsearch, might be more efficient in memory usage. }. The following scripts are plain Tcl, they don't use the Tk GUI toolkit (there's a separate chapter for those). 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. which is shorter and simpler, but meddles more directly with the stack. From Grade School to Raindrops. 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:). to make it understand and do things that before raised an error, the easiest way is to write a proc. They are for instance the building blocks of relational databases and spreadsheets. It was created by John Osterhout in 1988. 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. 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 result (0 or 1) is substituted for the first word of this command. {AND, OR, NOT} resp. Tests are done with this minimal "framework": The dot product of two vectors is a scalar. The Tcl track on Exercism has 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 my program set (nmax=30000) ends at 5-byte codes, so even by giving another test to force discovery of the real thing, it would never reach a 7-byte code. 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. Tcl - Environment Setup . If you are able to automate below few task, more then 50% of work (based on TCL) can be done easily. 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. The extending code what is prepended to the previous unknown body. An alternative solution could involve recursion (if you can follow this, youre advanced! 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. $ mkdir ~/cs498gpl/exercises/tcl $ cd ~/cs498gpl/exercises/tcl. The following "General Problem Solver" (for small values of General) uses heavy metaprogramming: it. The ebook version (PDF format) is available from Gumroad .. # This filter collects its input (should be finite;-) into a list: # $ streamlist {foo bar grill a} | sort | collect => a bar foo grill. 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!). 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. Compared to an RPN language, hypot would be. 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;-). All the rest would be there. 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. 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++. To extend Tcl, i.e. 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. 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}. with our unique blend of learning, practice and mentoring. with automatic analysis Tcl is a popular and widely used cross-platform script programming language that achieves significant productivity gains when used by skilled engineers. The Tcl track on Exercism has 122 exercises to help you write better code. 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. Threads are for people who can't program state machines.". Exercise 1 - Tcl procedure. This is something like the Goedel number of the corresponding code. 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. 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. 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. 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). Length: 3 days (24 Hours) Tcl has become the de facto standard embedded command language for Electronic Design Automation (EDA) applications. 71 coding exercises for C on Exercism. (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. 122 exercises This makes sense, even in Tcl, where one might implement them as. of your code and 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. The pattern, is a kind of conditional in J, which could in Tcl be written. 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). Tables are understood here as rectangular (matrix) arrangements of data in rows (one row per "item"/"record") and columns (one column per "field"/"element"). So, put the following source code in a test.tcl file. 122 exercises to help you write better code. Get better at programming through fun, rewarding coding exercises that test your understanding of concepts with Exercism. The first and second arguments are the class (disregarded here, as the dash shows) and the value, the rest is up to the coder. Functions in Tcl are typically written with the proc command. 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. 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). Hence, streams can be (and typically are) nested for processing purposes. 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." 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. personal mentoring, In this article, we will know how to use procedures in TCL. A Functional Style and Its Algebra of Programs. Here is a simpler way that allows to extend unknown "in place" and incrementally: We let unknown "know" what action it shall take under what conditions. 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. Proc above programming language such as C, Java, Python, etc do something with db ( key... Into a list of two vectors is a scalar how to use procedures in Tcl proc 's arg. Letter and Legal paper formats are popular in the algebra introduced here, with a handler for all files... The entire syntax of Tcl is a kind of conditional in J, which at Backus like! Alternative solution could involve recursion ( if you can follow this, youre advanced code what is prepended to previous! 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