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. This way, they are "pure values" and can be passed e.g. $ mkdir ~/cs498gpl/exercises/tcl $ cd ~/cs498gpl/exercises/tcl. The source code is compiled into bytecode, which is later interpreted by the Tcl interpreter. So, on a morning dogwalk, I thought out this strategy: Here's this version. 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. Clif is the author of the TclTutor package2 and the books Tcl/Tk for Real Programmers and Tcl/Tk: A Developer's Guide3. But I notice more and more that, on my way to functional programming, my proc bodies are a single call to expr which does all the rest (often with the powerful x?y:z operator). 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:-) }. 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. They are however better reusable than the multable proc above. 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). 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. 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. Indexes: As shown, we can retrieve all data by sequential searching over array names. See the examples soon to come. They think it's a programing (like software programing) and they are in VLSI Industry to do some hardware related job. (in a fantasy OO style): which, I admit, reads definitely better. In other words, a tautology. 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 #-- Two abbreviations for frequently used list operations: #-- So let's try to implement "mean" in tacit Tcl! However, most of these share the features. The book includes a short introduction to TCP/IP, as well as longer introductions to writing client . Functions in Tcl are typically written with the proc command. 1. In addition, for all procs, even without docstring, you get the "signature" (proc name and arguments with defaults). Introduction to the Tcl 3 Language The next ve chapters constitute a Tcl language tutorial. Adding "records" to the table is as easy as. TCL Scripting Training. 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. Tcl was developed initially for Unix. Tcl (pronounced "tickle" or as an initialism) is a high-level, general-purpose, interpreted, dynamic programming language.It was designed with the goal of being very simple but powerful. 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. 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. All the rest would be there. They are for instance the building blocks of relational databases and spreadsheets. Of course, with growing databases we may reach memory limits: arrays need some extra storage for administration. 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. 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. 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. 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. Clif first learned to program in high school in machine language on a Monroe 600 programmable . to make it understand and do things that before raised an error, the easiest way is to write a proc. 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. It does so by adding the values of the hex digits: Stacks and queues are containers for data objects with typical access methods: In Tcl it is easiest to implement stacks and queues with lists, and the push method is most naturally lappend, so we only have to code a single generic line for all stacks and queues: It is pop operations in which stacks, queues, and priority queues differ: Priority (a number) has to be assigned at pushing time by pushing a list of two elements, the item itself and the priority, e.g.. 560 pages, Paperback. One point that was new for me is that the distinction between operators and operands is not cast in stone. ", http://csc.smsu.edu/~shade/333/project.txt, https://en.wikibooks.org/w/index.php?title=Tcl_Programming/Examples&oldid=3678753, Common Lisp: (documentation 'foo 'function), The ratio between the longer and the shorter side of an A format is constant, pop: retrieve and remove one object from the container, in a stack, the most recently pushed object is retrieved and removed (last in first out, LIFO), in a (normal) queue, it is the least recently pushed object (first in first out, FIFO). 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;-). 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. This simple example invokes expr if the "command" is digestible for it: Imagine the makers of Tcl had failed to provide the if command. by one the binary operators +-*/. Here's typical set operations. # 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. TCL is shell application that reads TCL command from its standard input or from a file and gives desired results. Especially constants (like "true" and "false" in Boolean algebras) can be equally well expressed as neutral elements of operators, if these are considered variadic, and having zero arguments. Tcl is much similar to other unix shell languages like Bourne Shell (Sh), the C Shell (csh), the Korn Shell (sh), and Perl. Should you need a unit matrix (where the main diagonal is 1, and the rest is 0), just call outProd with a different function (equality, ==): which just requires expr's equality to be exposed too: One of the fascinations of functional programming is that one can do the job in a simple and clear way (typically a one-liner), while using a collection of reusable building-blocks like lmap and iota. For example, in. Especially, indexing the isa field allows iterating over "tables" (which we still don't explicitly have! The following example code opens a file, configures it to binary translation (i.e. $ wish ex1proc.tcl. Discover new exercises as you progress and get engrossed in learning new concepts and improving the way you currently write. true. 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? 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. The following scripts are plain Tcl, they don't use the Tk GUI toolkit (there's a separate chapter for those). 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. Just like functions, procedures take arguments and return some value. 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. #-- We need basic scalar operators from expr factored out: "length mismatch [llength $a]!= [llength $b]". Tcl/Tk for Programmers: With Solved Exercises that Work with Unix and Windows Memory Exercises: Memory Exercises Unleashed: Top 12 Memory Exercises To Remember Work And Life . For instance, reading a file in one go: can be simplified, without need for the data variable, to: This is in some ways similar to LISP's PROG1 construct: evaluate the contained expressions, and return the result of the first one. If they don't, we have found a fact that isn't dependent on the variable's value, and the resulting constant is returned, otherwise the unsolved expression: with a helper function in that reports containment of an element in a list: which means, in expr terms, {(!$a || $a) == 1}, for all values of a. I added converters between characters and integers, and between strings and lists (see the dictionary below). Single bytecodes are executed, only to measure their effect on the stack. Procedural, OO, functional; builtin event loop for network programming and asynchronous file I/O. 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. (One might truncate the list at front if it gets too long). of your code and Tables are understood here as rectangular (matrix) arrangements of data in rows (one row per "item"/"record") and columns (one column per "field"/"element"). There are over 200 exercises with solutions that run on both Unix and Windows platforms. Tcl/Tk for Programmers is an introduction to the high-level Tcl/Tk scripting language for experienced programmers with either Unix or Windows background. A very simple control structure (one might also call it a result dispatcher) is the K combinator, which is almost terribly simple: It can be used in all situations where you want to deliver a result that is not the last. The goto command is defined "locally", and deleted after leaving the state machine it is not meaningfully used outside of it. Arguments are pushed on the stack, and the result of the "software", the stack at end, is returned. A collateral advantage is that all expressions are braced, without me having to care. Implementation is as a "little-endian" list of integers, where bits 0..31 are in the first list element, 32..63 in the second, etc. In TOOT, the values of objects are represented as a list of length 3: the class name (so much for "runtime type information":-), a "|" as separator and indicator, and the values of the object, e.g. If you are able to automate below few task, more then 50% of work (based on TCL) can be done easily. In Tcl, a sensible implementation for compact data storage would be as a list of lists. In Tcl, the two ways of reading a file are a good example: The second construct may be less efficient, but is robust for gigabyte-sized files. 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? So what about a thin abstraction (wrapper) around this recurring pattern? Tcl/Tk 8.2.3 and Tcl/Tk 8.3.0 under windows. Before we start, a word of warning: maintaining state of a procedure is done with default arguments that may be rewritten. Creating a new syntax for a DSL would defeat the purpose of Tcl. Tcl 8.5 Network Programming (2010) , by Kocjan and Beltowski, is targeted towards building network-aware applications using Tcl and includes coverage of many Tcl libraries and extensions. The "main routine" is a single line that dumps all files given on the command line: Sample output, the script applied to itself: Roman numerals are an additive (and partially subtractive) system with the following letter values: Here's some Tcl routines for dealing with Roman numerals. 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 let's get the pieces together. 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