ITEC 380 2016fall ibarland

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language-families
Families of languages

Three things to consider, in a language:

• Syntax (what strings are legal programs?)
• Semantics (what is the meaning of the program?)
• Pragmatics (what is in/convenient and un/suprising, about different syntactic constructs, and their semantics)

Families of languages:

• low-level
• procedural
• object-oriented
• scripting
• functional
• declarative

  What are various languages you've used?





These categories are (a) very blurry; (b) not informative -- not the fundamental building blocks of language-features.


low-level -- understading the language's semantics requires knowledge of the hardware it runs on.
  C ("high-level assembly"),
   assembly

Procedural: organize code in procedures (like functions/methods, but may have side-effects and not return values)
  Ada - lots of safety features (and, requirements)

scripting: easy to work with files, OS calls, manipulate strings and I/O; glue together parts of other large projects
    perl, python, javascript, php
    ruby -- everything is an object, e.g. 3.plus(4)
    javascript -- uses instance-based inheritance, not class-based inheritance

object-oriented:   objects; inheritance (allows code re-use and code specialization)
                              you don't "call a function", you do "message passing" -- give an object a method (that is, request it to do something)
    Smalltalk -- first O.O. lang;  
    Java,  C++,  C#, Alice -- has some primitive types that are not objects (e.g. int, double, boolean, char)

functional: organize code into pure functions (no side-effects, always *return* value)
                 (If you give the same function the same inputs later, you MUST get the same answer.)
                 No mutation -- don't change variables or fields.
                 higher-order functions: can pass a function as an input, to be (used by) other functions!  ...Can create new functions that didn't exist at compile-time.
                 Tends to have lots of small functions (only a few lines long).
   Lisp (1965 -- 2nd oldest language in use, after Fortran);
                 evolved to Scheme (a streamlined lisp),
                 scheme evolved into racket (an industrial-strength scheme)
   racket, F#
   Haskell -- *pure* functional; lazy (and, very very abstract).

Declarative language -- your program gives the defining properties of the solution, but NOT how to find it.
                                      (don't talk about loops, or variables, or updates; talk about *specifying* the result.)
    Prolog
    SQL, Excel

high-level domain-specific langauge:
   Mathematica, MatLab

html, markup:
    They are data -- not languages.


Side-effect: making a change that can be seen elsehwere.
 Examples: setting global variables; e.g. current-time-of-day; and I/O.

A history overview

  name  yr  family  feature(s)/notables  (descendents/related)  example
  TM, lambda calculus 
  machine / hardware switches (incl. Babbage's Analytic Engine)
  assembly
  Lisp; Scheme, ML, Haskel, F#
  Fortran; PL/I; Algol; 
  SmallTalk; C++, java, C#
  Ada; 
  sh, csh, Tcl/Tk, perl, python, ruby
  rpn; postscript (printer is the interpreter; req'd M68000, not 8088,6502); pdf
  prolog (Japanese "4th wave")
  Basic (Apple II ROM; line#s; goto;'gosub' but no params (only globals) (recursion?!)), 
     http://www.jenutech.com/images/HomeSweetGoto10.gif
     http://theinfosphere.org/File:Gotohell.jpg
  Pascal (teaching; nested procedures)

  language popularity index
  poster: programming languages history
  The hello world collection

- examples: enscript -o foo.ps       (wimpout.ps)
      Example: enscript -o foo.ps ; cat foo.ps ; open foo.ps
      Example: cat wimpoutBoard.ps ; open wimpoutBoard.ps
   also, sh: Example: cd ~/Unix 
                      find . -name \*.ps -print
                      find . -name \*.ps -print | grep -i wimpout

- other notables:
  * postscript
  - C, Ada, Fortran, Pascal, Rexx, ...
  - Smalltalk, Java, C++, C#, ...
  - APL; Mathematica; Matlab
  
  - javascript, perl, etc;   html ?  -- no; data.  But, .css.
  - sh/csh, .bat, applescript; scriptable photoshop?
     Example: cd ~/Unix 
              find \*.ps
              find \*.ps | grep -i wimpout
     Note that we are calling functions.  (How are arguments passed?)
  - a *programmable* calculator.
  * MS Word "macros" and mailing-list scripts
  - abacus-instructions ?

Link: "A new language for phone networks" (declarative; based on F#)
www.technologyreview.com/communications/23330/?a=f

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©2016, Ian Barland, Radford University Last modified 2016.Sep.02 (Fri)

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