Exploring metaprogramming using Ruby language

Exploring metaprogramming using Ruby language

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  Exploring metaprogramming using Ruby language A brief introduction Harshal Ganpatrao Hayatnagarkar PhD Candidate in Dept. of Computer Science 1 Friday, October 3, 2014
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  Engineering marvels FordModel T (approx. 1918) Tesla Model S (2010) 10/24/2014 2
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  Assembly Lines: Processmarvels Ford Model T Assembly Line Tesla Robotic Assembly Line 10/24/2014 3
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  Assembly Lines: Processmarvels People building cars A worker on assembly line does same task repetitively, item after item and day after day. People building robots building cars Is this like programming? People building robots build robots building cars What is this analogous to? Courtesy: http://stackoverflow.com/questions/3468246/whats-the-use-of-metaprogramming 10/24/2014 4
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  Metaphor … Peoplebuilding robots building robots… building cars What is this analogous to? 10/24/2014 5
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  Meta-programming • Meta(‘beyond’ in Greek) + programming  Programming Abstraction – Similar to meta-data, meta-model, meta-physics and so on. • “Writing of computer programs that with ability to treat programs as their data, as it meant that a program could be designed to read, generate, analyse and/or transform other programs, and even modify itself while running. In some cases, this allows programmers to minimize the number of lines of code to express a solution (hence reducing development time), or it gives programs greater flexibility to efficiently handle new situations without recompilation.” - Wikipedia 10/24/2014 6
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  Revelation Data-Code Duality 10/24/2014 7
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  Two aspects ReflectionGenerative programming 10/24/2014 8
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  Reflection • Abilityof a computer program to examine and modify the structure and behavior (specifically values, meta-data, properties and functions) of the program at runtime. – Metalanguage in which metaprogram is written. – object language, programs written in which are manipulated. – reflection or reflexivity is ability of a programming language to be its own metalanguage. • Fairly common in programming languages – C++ (limited) – Java (+ other JVM languages), C# (+ other CLR languages) – JavaScript, Python, PHP, Ruby 10/24/2014 9
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  Generative Programming •“A style of computer programming that uses automated source code creation through generic frames, classes, prototypes, templates, aspects, and code generators to improve programmer productivity.” - Wikipedia • For example, – Internal to language: C/C++ preprocessor macros, C++ templates, LISP macros, Ruby/Python/PHP evaluations. – External: Code generation templates. 10/24/2014 10
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  Ruby Programming Language • Dynamic, reflective, object-oriented, general-purpose programming language. • Influenced by Perl, Smalltalk, Eiffel, Ada, and Lisp. • Supports multiple paradigms functional, object-oriented, and imperative. • With dynamic type system and automatic memory management. Yukihiro "Matz" Matsumoto 10/24/2014 11
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  Meta Object Protocol • Everything is an object, including classes. • Method calling is analogous to message passing where arguments are payload. 10/24/2014 12
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  Open Classes 10/24/201414
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  Dynamic methods 10/24/201415
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  Dynamic methods Rubyon Rails – ActiveRecord example 10/24/2014 16
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  Generative Programming •Code generation – one or more levels – ‘eval’ expression family – Takes source code in string form and embed in current context. 10/24/2014 17
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  Two-level generation •Code generating code generating code Level 1 Level 2  ‘Level 1’ eval  ‘Level 2’ eval 10/24/2014 18
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  Pitfalls • Metabugs? – Bugs generating bugs generating… – And there is no ‘programs debugging programs debugging programs…’. • Increased code complexity 10/24/2014 19
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  Further exploration… •Model-driven development • Domain-specific languages • Ruby on Rails for web development framework – An example of metaprogramming features. 10/24/2014 20
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  Questions? And thankyou for your interest ! 10/24/2014 21