Scripting languages

What is a scripting language?

From Wikipedia we read that:

Scripting languages (commonly called scripting programming languages or script languages) are computer programming languages that are typically interpreted and can be typed directly from a keyboard. Thus, scripts are often distinguished from programs, because programs are converted permanently into binary executable files (i.e., zeros and ones) before they are run. Scripts remain in their original form and are interpreted command-by-command each time they are run. Scripts were created to shorten the traditional edit-compile-link-run process.

Of course any self respecting computer scientist knows that definition is meaningless, because a language is a mathematical constructand is not tied to its implementation. You can write a C interpreter, for example (and there are some). You can also write a compiler for any 'interpreted language' (of course the term 'interpreted language is also meaningless). And there are theoretical constructs (Futamura projections) that given any interpreter are able to build a compiler from it (you could implement them even in practice, though it would be terribly inefficient).

However, any other definition would be misleading as well: if you define a scripting language as a language you can use to "script" (as in "bash script"), then you've got definition that's even more stupid. bash is a scripting language, and so it is Python. However, if someone writes an application that is scripted in C, C becomes a 'scripting language').

Both definitions have an additional problem: scripting languages are considered somewhat inferior to 'non-scripting languages'. Some even use the term 'true programming languages' (and this 'true programming languages' are usually considered to be C and C++, for example).

Lisp, Haskell, OCaml, Prolog

In this dissertation on 'scripting languages', Lisp is quite emblematic. Lisp can be compiled (there are some Lisp compilers around). But Lisp can also be interpreted. This is one of the most widespread Lisp environments (and it is an interpreter). Moreover, in Emacs you can just run some Lisp snippets. And Emacs itself is scripted in Lisp (thus Lisp would be a scripting language according to the second definition). However, no one can assert that it is not a 'true' programming language. Emacs itself is a beautiful (and complex) piece of software, and a lot of 'real' (and extremely difficult) stuff in the AI field has been written in Lisp.

Haskell can be another example. Hugs is an interpreter, ghc is both an interpreter and a compiler. And Haskell is even statically typed (so you see, being dynamic is not necessary ). The very same applies for OCaml or Prolog. And all thislanguages have been used by the most theory-oriented computer scientist toimplement real programs.

I suppose nobody would say that Lisp or Haskell are 'scripting languages' (even if according to the definitions they are -- Haskell is used in many configuration tools by Linspire programmers).

Bash, Perl, Python, Ruby.

All this languages have been labeled as 'scripting languages'. And in fact according to definitions, they are. However, they are very different languages.

Bash is a very simple language designed to do simple things. Unix system administrators used it intensively (along with awk and sed and other utilities) to automate many repetitive tasks. Although this is surely 'programming', in some sense it's different from programming an application from scratch. Some even consider it a 'lower level' kind of programming (and surely we must recognize that skills involved in writing a boot script are different from skills used to write a compiler)

Perl was born in this environment: its goal was textual manipulations and interactions between processes in a system. It is a nicer alternative to bash + awk in many situations. Later it has been added a fully fledged object model, but in the while it has been used to write very complex applications that go outside the 'lower level programming domain' that is usually associated with 'scripting'. Even though I don't like Perl anymore, it is a general purpose language, with the same dignity of C or C++.

The 'scripting language' monicker is not fitting anymore. And it is even less fitting for Python. Python has been an object oriented programming language from the beginning. Good software engineering practices have always been employed. However, many consider it just another scripting language. And of course Python makes a great scripting language.

The domains in which Python excels are the same in which Java is used, for example. However, Python can be used for scripting, too. That is to say... some (and I'd be tempted to say 'most' ) 'scripting languages' can be used both as general purpose languages and automation/scripting.

The reason why they can be used for automation/scripting and that they are easier to use and we can write programs faster. The development cycle is faster, too. And to me, they all seem good properties.

I think that the very same features that make Python (or Ruby) great for scripting, make it even greater for general purpose programming. That is to say we should consider a 'scripting language' not a poorer language, but a better one (yeah, of course this is exaggerated, since there are languages suited for scripting that are not suited for general purpose programming -- AppleScript and bash, for example).