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Programming languages - what are the differences between them?

Comparing the programming languages ... the same program in 10 languages

How do I add one to a variable? Some languages have a ++ operator, other languages allow you to use +=, others have an incr command, and in some you have to write a long(er) assignment statement.

How do I set up a variable in the first place? In some languages, simply mention a variable and it will appear as if by magic, nicely initialised to zero or an empty string. In others you need to set an initial value. And in others you need to tell the computer the type of data it will contain as well as defining the type.

How do I output results? There are all sorts of puts and print statements, and even operators such as <<. And how you join values on the same line, and add the end of line character, is a further question.

I can teach you any of ten languages, and one of the big advantages I have of knowing so many is that I can compare and contrast for you if you're in the process of converting, or if you're learning anew and have vague recollections from School days. [Course Schedule]

The sample program I've written takes a variable up from nothing / zero to 7, displaying its value twice and incrementing it twice each time around a loop. Results - consistently in all the languages - look like this:
   wizard:incr graham$ ./incr.sh
   xxx 1
   yyy 1
   xxx 3
   yyy 3
   xxx 5
   yyy 5
   xxx 7
   yyy 7
   wizard:incr graham$


The programs differ - here are links to the code to do that in ... C C++ Java Lua PHP Perl Python Ruby Shell (Bash) and Tcl.

Let's look at just three examples within this main article. Here's the program in Perl:

  #!/usr/bin/env perl
  while ($n < 7) {
    print "xxx ",++$n,"\n";
    print "yyy ",$n++,"\n";
  }


in Tcl:

  #!/usr/bin/env tclsh
  set n 0
  while {$n < 7} {
    puts "xxx [incr n]"
    puts "yyy $n"
    incr n
  }


and in C++:

  #include <iostream>
  using namespace std;
  int main() {
    int n = 0;
    while (n < 7) {
      cout << "xxx " << ++n << endl;
      cout << "yyy " << n++ << endl;
    }
  }


In Perl, the variable is automatically created and assigned an empty value when first encountered, with Perl deciding it has to be a number when it's incremented. In Tcl, variable (almost) always need to be initialised, but you don't need to tell the system the type of data they will contain. And in C you must declare the type, and it's strongly recommended that you intiialise; if you don't, the variable takes the initial value form whatever was left in memory from the previous program.

Both Perl and C++ have the ++ operator to increment a variable. If the ++ is written before the variable name, then it's incremented before it's used for anything else in the context in which it's written. In Tcl, the incr command provides a shortand way of incrementing a variable.

C++ variable names never start with a $. Perl (scalar) variable names always start with a $. And in Tcl, you specify a $ in contexts where you are just using the existing contents of a variable, but never in the contexts where you are (or may be) setting the value.

Perl and Tcl programs start at the top of the file, whereas your C++ program starts at the function called main.

In all 3 of the example languages I have chosen, you indicate the scope of a loop using a {} block. But please note that differs when you look at other languages in other examples such as Ruby (the word end) and Python (where it's done by spacing)

C++ is a compiled language - you need extra instructions to convert the code above into a runnable program. Tcl is a pure interpretter language - each line is interpretted as the program runs (quick to start, slower to run if you have loops). Perl, and most of the other languages for which I've supplied examples, use a Virtual Machine approach which means that the source code is only interpretted once - a little slower to actually start the program than an intepretter, but then much faster to run, and without the hassle of C++'s extra instructions.

If you're unsure which language is right for you, and you're not too far from us, please let me know and we'll arrange for you to pop in for an evening to help you make a choice. There's a lot more to the choice than just the syntax of the source.
(written 2012-06-27, updated 2012-06-30)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
G908 - Well House Consultants - Language Comparisons
  [3169] Rekeying a table - comparison in #Ruby #Perl and #Python - (2011-02-14)
  [3112] Public and private courses - subjects available for 2011 - (2010-12-29)
  [3003] What will we be teaching in six years? - (2010-10-17)
  [2947] Teaching Lua to a Perl advocate - (2010-09-06)
  [2866] Ruby - how does it compare and where is it the right language? - (2010-07-11)
  [2755] Books in the store in the USA - still a portent of the UK market to come? - (2010-05-08)
  [2700] The same very simple program in many different programming languages - (2010-03-31)
  [1990] Speaking all the languages - (2009-01-12)
  [1717] Q - Should I use Perl or Python? - (2008-07-23)
  [1582] Ruby, C, Java and more - getting out of loops - (2008-03-19)
  [209] FAQ - Perl or PHP - (2005-02-11)

Q102 - Choosing your language
  [3764] Shell, Awk, Perl of Python? - (2012-06-14)
  [3619] Ruby v Perl - a comparison example - (2012-02-21)
  [3558] Python or Lua - which should I use / learn? - (2011-12-21)
  [2536] All the Cs ... and Java too - (2009-12-13)
  [2535] When should I use Java, Perl, PHP, or Python? - (2009-12-13)
  [2507] Admission - (2009-11-19)
  [2048] Learning to program in PHP, Python, Java or Lua ... - (2009-02-19)
  [2001] I have not programmed before, and need to learn - (2009-01-19)
  [76] Learning to program in - (2004-10-07)


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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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