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TCL

TCL. Matthew Hamod Nicholas Will. Problem Domain. Designed to act as a powerful command language (scripting language) Could be implemented as a library package Not intended to be a standalone language Easy to create new features as part of the language. Historical Context.

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TCL

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  1. TCL Matthew Hamod Nicholas Will

  2. Problem Domain • Designed to act as a powerful command language (scripting language) • Could be implemented as a library package • Not intended to be a standalone language • Easy to create new features as part of the language

  3. Historical Context • Developed by John Ousterhout • Stands for "Tool Command Language" • GUI applications becoming popular • Tools for creating GUI applications were complex • Some features of Tk may have influenced Java development

  4. Evolution of the Language • Started as a Unix only language • Eventually able to run on Windows and Mac • Started as a slow language • Originally, TCL code was completely interpreted • Brian Lewis created a bytecode compiler • Increased speeds by 5-10x

  5. Language Concepts • ; or newlines are command separators • } are command terminators • A word that starts with a $ is a variable • i.e. $variable • $variable(index) is an array • # is used for one line comments • Ending a line in a \ allows the comment to span multiple lines • A comment should only be placed where a command is expected

  6. Language Concepts • Strings • Don't need quotes • set greeting Hello! # this is perfectly valid • Quotes or braces are used for grouping • set example "this is one group" • set example {this is another} • String groups can span multiple lines and the newline will be included

  7. Examples of Use

  8. Examples of Use

  9. Comparison to Python • Both can be used as an extension or as a standalone language • TCL is weaker on data structures • TCL executes typical code much slower than Python • TCL lacks features needed for writing large programs (for instance, modular namespace) • Tk toolkit adds namespaces and increases speed

  10. Comparison to Perl • TCL passes arrays by name • Perl can pass arrays by reference or by value • Perl can analyze a script for errors in syntax without execution • TCL cannot, because it executes one line at a time • TCL is better at being used as a configuration file parser • TCL's command line library is well suited to being used from Perl

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