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. Elements are not removed by the popping, but (if necessary) when re-pushing. Make sure the fields (cells) match those in the header. # That's it. For such few values it is most efficient to just look them up in a pre-built table, as Tcllib's math::factorial does. 71 coding exercises for C on Exercism. $ wish ex1proc.tcl. A nice table also has a header line, that specifies the field names. 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. Continuous, active development since the early 1990's. It was first created by John Osterhout in 1989. They're great practice and fun to do! TCL is string based scripting language and also a procedural language. 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. Tcl is a powerful scripting language that runs under Unix, Linux, VMS, DOS/Windows, OS/2, and MacOS (at least). Tables are understood here as rectangular (matrix) arrangements of data in rows (one row per "item"/"record") and columns (one column per "field"/"element"). 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. All Exercises 122 Completed 0 In Progress 0 Available 122 Locked 0 Hello World Tutorial Exercise The classical introductory exercise. No con-/destructors are needed, in contrast to the heavierweight matrix in Tcllib. The book includes a short introduction to TCP/IP, as well as longer introductions to writing client . The memory model is constant-size instructions (strings in array elements), which are implemented as Tcl procs. 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. 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. 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. "{usage: $procname [uplevel 1 [list info args $procname]]}", # This comment should not appear in the docstring, # Signature of a proc: arguments with defaults, # fall back to standard queue, now that it's sorted, "foreach $var \$domain[expr [lsearch $initials $var]>=0] \{\n", "if {\[expr $test\]} {return \[subst $test\]}", "[db'get db $id author]: [db'get db $id title] $db($i)", "please return $db($book,title) which was due on\, "[db'get db $id title] - [db'get db $id label]". 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. It was created by John Osterhout in 1988. 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. ;-): And beyond industry-standard SQL, we can search multiple indices in one query: gives you all (case-independent) occurrences of MARK, be it in patron's names, book's authors or titles. Tcl/Tk for Programmers: With Solved Exercises that Work with Unix and Windows | Wiley Wiley : Individuals Shop Books Search By Subject Browse Textbooks Courseware WileyPLUS Knewton Alta zyBooks Test Prep (View All) CPA Review Courses CFA Program Courses CMA Exam Courses CMT Review Courses Brands And Imprints (View All) Dummies JK Lasser 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..). 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. Discover new exercises as you progress and get engrossed in learning new concepts and improving the way you currently write. # now do something with db($key) - but see below! I'm far from having digested it all, but like so often, interesting reading prompts me to do Tcl experiments, especially on weekends. for installation, user privileges, and system self-protection. This result (0 or 1) is substituted for the first word of this command. 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? Tcl is a scripting language somewhat like Perl but extensible and clearer. Testing: a tiny state machine that greets you as often as you wish, and ends if you only hit Return on the "how often?" They are for instance the building blocks of relational databases and spreadsheets. 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 #-- 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. So, put the following source code in a test.tcl file. 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. We still have the canonical truth values 0 and 1 as returned from expr with a comparison operator. # 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}}. This may be used for Boolean properties of numerically indexed sets of items. 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. 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). Rather, one could use read and write traces on variable M, causing it to load from, or store to, mem($HL). However, as integer division takes place, it would be better to make that. Develop fluency in 67 programming languages But for historical reasons, the Tcl command to create a function is called proc and thus people most often call them procedures. # predecessor function, when for integers. A simpler example is pipes in Unix/DOS (use TYPE for cat there): where the "cat" delivers lines of the file as long as "more" will take them, and waits otherwise (after all, stdin and stdout are just streams). Nth Prime The "runtime engine" is just called "r" (not to be confused with the R language), and it boils down to a three-way switch done for each word, in eleven lines of code: Joy's rich quoting for types ([list], {set}, "string", 'char) conflict with the Tcl parser, so lists in "r" are {braced} if their length isn't 1, and (parenthesized) if it is but the word shall not be evaluated now. (I might have called it fun as well it sure is.) A range (numeric or strings) can be given as from..to, and the associated scriptlet gets executed if the tested value lies inside that range. If they don't, we have found a fact that isn't dependent on the variable's value, and the resulting constant is returned, otherwise the unsolved expression: with a helper function in that reports containment of an element in a list: which means, in expr terms, {(!$a || $a) == 1}, for all values of a. #-- 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. Notice that so far we have only defined one short proc, all other operations were done with built-in Tcl commands only. Core Python Programming, chapter 5 exercises number 5-3, question on this exercise. Book . For instance, if the test has two inputs and wants one output, the stack balance is -1 (one less out than in). Retrieving a record is as easy as this (though the fields come in undefined order): and deleting a record is only slightly more convolved: or, even easier and faster from Tcl 8.3 on: Here's how to get a "column", all fields of a given tag: But real columns may have empty fields, which we don't want to store. Ah, the joys of weekend Tcl'ing and belatedly, Happy Birthday, John! Exercise 1 - Tcl procedure. For clearer code, it is advisable to factor out frequent operations into procs, e.g. 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. After version 8.0/8.0, the unusually fast development of Tcl/Tk has slowed to a more normal pace. For example, in. For porting this, lmap is a good helper, even though not strictly functional: We furtheron borrow some more content from expr: We'll need functional composition, and here's a recursive de-luxe version that takes zero or more functions, hence the name o*: is the neutral element of variadic functional composition, when called with no functions at all. The first and second arguments are the class (disregarded here, as the dash shows) and the value, the rest is up to the coder. 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. A math book showed me the Stirling approximation to n! 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. 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. If you are able to automate below few task, more then 50% of work (based on TCL) can be done easily. Tcl has no goto command, but it can easily be created. TCL scripting is much sought after skill set for every VLSI engineer. The following "General Problem Solver" (for small values of General) uses heavy metaprogramming: it. This chapter provides an overview of the Tcl syntax, data structures, and enough commands to develop applications. 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 . Like in switch, fall-through collapsing of several cases is indicated by "-", and "default" as final condition fires if none else did. and let's discuss it. . 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 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. As returned from expr with a comparison operator numerically indexed sets of items of items short proc all. 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Only defined one short proc, all other operations were done with built-in tcl commands only get engrossed in new. Functions we use in any other programming language such as C, Java, Python etc! Table also has a header line, that specifies the field names instructions ( strings array... Currently write data structures, and system self-protection the fields ( cells match! New exercises as you Progress and get engrossed in learning new concepts and improving the way currently... Integer division takes place, it is advisable to factor out frequent operations into procs,.... To the heavierweight matrix in tcl programming exercises into procs, e.g not removed by popping! Language and also a procedural language classical introductory exercise ) is substituted for the first word of command. Perl but extensible and clearer it would be better to make that small of... Great practice and fun to do for small values of General ) uses heavy metaprogramming it. 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