Scripting Languages

www.php.net

www.python.org

www.ruby-lang.org

www.perl.org

www.tcl.tk/

http://dmoz.org/Computers/Programming/Languages/Scripting

www.vendian.org/language_year

Scripting?

A short, somewhat misleading, way to say programming in a very high level language

But what is a VHLL?

It depends on who you talk to...

Is Prolog a scripting language? Scheme? Java? Javascript?

I claim no..

But maybe important: www.oreillynet.com/pub/wlg/3190

Fundamental Properties of Scripting

Easy to use

• Typeless?
• Interpreted
• Simple?

Lot's of available functionality

• Built-in data structures (lists, associative arrays)
• Built-in string processing (strings and regexps)
• User community writes lots of modules
• Network, DB, XML, GUI, WWW, etc., etc.

Extensible

• "Easy" to write native code that is accessible from script

Embeddable

• "Easy" to access script from native code
• Is this an architectural style? (embedded interpreter)
• E.g., http://www.gimp.org/scripts.html?

Dynamic

• Code is data, data is code
• Typically have an "eval" command

But is this software engineering?

Scripting languages can:

• Be ill defined
• Change their semantics at will
• Encourage BAD programming
• Have little support for modularity
• Dynamically fail (e.g., octal input)

Uses of scripting in SE

Prototyping

• write a prototype in a scripting language
• select critical piece, convert to system language
• repeat until performance requirements are satisfied
• package into an executable

Is this a new software development model?

CBSE Glue (CBSE==Component-Based-SE)

• Buy components or code your own in a system PL
• Glue together with a scripting language
• Revert to SD process above if needed

Tcl calling DLLs: http://www.elf.org/ffidl/

Perl calling DLLs: http://dada.perl.it/

Tcl DII into CORBA: http://www.cerc.wvu.edu/iss/TclDii.htm

A Python ORB: http://www.fnorb.org/

Test harnesses

• write scaffolding in scripting language
• optionally make use of tools like SWIG (http://www.swig.org/)
• easy to create and update tests
• can create automatic "user" scenarios (with, e.g., Expect ( http://expect.nist.gov/)
• Whole test packages, e.g., Dejagnu ( http://www.gnu.org/software/dejagnu/)

Other uses

Other scaffolding -- skeletons, stubs, input generators, output summarizers

Special development tools -- project-specific code generators, file managers, report generators, etc.

Automating anything you can in the SE process

Do many IDE's support a scripting language?

Can Eclipse use a scripting language?