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Functional Programming 1 Haskell Basics

Functional Programming 1 Haskell Basics. Dr. Ahmed Sallam. Reference. Main: Introduction to Haskell By Brent Yorgey Further. Functional Programming. Function is the atom of the language, and can be used exactly as any other sort of value.

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Functional Programming 1 Haskell Basics

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  1. Haskell Basics Functional Programming1 Haskell Basics Dr. Ahmed Sallam

  2. Reference • Main: Introduction to HaskellBy Brent Yorgey • Further Haskell Basics

  3. Functional Programming • Function is the atom of the language, and can be used exactly as any other sort of value. • Programming style is centered around evaluating expressions rather than executing instructions. Haskell Basics

  4. Haskell • Named after logician Haskell Curry. • It was created in the late 1980 by a committee of academics where everyone had his favorite functional language. • It combines some of the best ideas from existing languages, and a few new ideas. Haskell Basics

  5. Haskell Characteristics • Functional • Pure • Lazy • Statically typed Haskell Basics

  6. Haskell Characteristics • Pure • Immutable declarations • Referential transparency Haskell Basics

  7. Haskell Characteristics • Pure • No side effects: (e.g. updating global variables) • Parallelism: evaluating expressions in parallel. • Lazy • Expressions are not evaluated until their results are needed. • Statically Typed • Each expression has a fixed type. (expression with errors will not compiled) Haskell Basics

  8. Basic concepts • Types • Haskell’s rich of types. • Clarify thinking in the program structure • Serve as documentation • Turns run-time errors into compile-time errors. • Abstraction • “Don’t repeat yourself” • Polymorphism • Higher order functions Haskell Basics

  9. Basic concepts • Wholemeanl programming • first solve a more general problem, then extract the interesting bits and pieces by transforming the general program into more specialised ones. Haskell Basics

  10. Declarations and Variables • Get in the mode Haskell Basics

  11. Basic Types • Int : +/- 2^n (Calculate n as following) • Integer: limited by your machine memory. • Float, Double: real numbers. • Bool: Booleans. • Char: Unicode Characters. • String Haskell Basics

  12. GHCI Tips • :load or :l is used to load .hs file. • :reload or :r is used to reload .hs file • :type or :t is used to ask for expression type • :? Is used to show help (show available commands) Haskell Basics

  13. Arithmetic • Note: mod operation • Note: negative numbers Grave Accent Haskell Basics

  14. Arithmetic • Casting must be explicit • fromIntegral : ineger to all • Round, floor, ceiling • Use (div) instead of (/) with integers Haskell Basics

  15. Logic • Comparisons: ( < , >, <=, >=, =, /=) • Combine : ( ||, && , not () ) Haskell Basics

  16. Logic • Else is mandatory Haskell Basics

  17. Function basic definition Haskell Basics

  18. Using function • Functions has the highest priority. • sum 5 n+1 3 parse as (sum 5 n) + (1 3) • If you want to pass n+1 as argument , write • sum 5 (n+1) 3 Haskell Basics

  19. Lists • a = 1 : [] • b = 3 : (1 : []) • c = [2,3,4] == 2 : 3 : 4 : [] Haskell Basics

  20. Function on lists • We can replace h with _ Haskell Basics

  21. Useful links • Haskell Portal • Haskell Platform Haskell Basics

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