XII Computer Science- Chapter 1-Function
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This document discusses computer science functions and their key concepts: - Functions are subroutines or blocks of code that perform a specific task and can be reused. They take parameters as inputs and return an output. - The interface of a function defines what it can do from the outside, while the implementation contains the internal code that carries out its behavior. - Pure functions always return the same output for given inputs, while impure functions may produce side effects or different outputs for the same inputs. - Examples demonstrate defining functions with and without parameters, recursive functions, and using functions to solve problems like determining if a number is even or odd.
XII Computer Science- Chapter 1-Function
- 1. XII- COMPUTER SCIENCE CHAPTER 1 FUNCTION
- 2. INTRODUCTION • The most important criteria in writing and evaluating the algorithm is the time it takes to complete a task. • To have a meaningful comparison of algorithms, the duration of computation time must be independent of the programming language, compiler, and computer used. • If a bulk of statements to be repeated for many numbers of times then subroutines are used to finish the task.
- 3. SUBROUTINES • Subroutines are the basic building blocks of computer programs. • Subroutines are small sections of code that are used to perform a particular task that can be used repeatedly. • In Programming languages these subroutines are called as Functions.
- 4. Function • A function is a unit of code that is often defined within a greater code structure. • A function contains a set of code that works on many kinds of inputs, like variants, expressions and produces a concrete output.
- 5. Function Specification • Let us consider the example a:= (24). a:= (24) has an expression in it but (24) is not itself an expression. • Definitions bind values to names, in this case the value 24 being bound to the name ‘a’. • Definitions are not expressions, at the same time expressions are also not treated as definitions. • Definitions are distinct syntactic blocks.
- 6. Parameters (and arguments) • Parameters are the variables in a function definition and arguments are the values which are passed to a function definition. • 1. Parameter without Type • 2. Parameter with Type
- 8. Parameter with Type With Data type Keyword Recursive Function name
- 9. Syntax for function definitions let rec fn a1 a2 ... an := k ‘fn’ function name. The names ‘a1’ to ‘an’ are variables indicating the identifiers used as parameters. The keyword ‘rec’ is required if ‘fn’ is to be a recursive function; A function definition which call itself is called recursive function.
- 10. Example to check whether the entered number is even or odd All functions are static definitions. There is no dynamic function definitions.
- 11. Interface Vs Implementation • An interface is a set of action that an object can do. • For example when you press a light switch, the light goes on, you may not have cared how it splashed the light. • an Interface is a description of all functions that a class
- 12. Key points • A class declaration combines the external interface (its local state) with an implementation of that interface (the code that carries out the behaviour). • An object is an instance created from the class. • The interface defines an object’s visibility to the outside world.
- 14. Characteristics of interface • The class template specifies the interfaces to enable an object to be created and operated properly. • An object's attributes and behaviour is controlled by sending functions to the object.
- 15. Example
- 16. Pure functions • Pure functions are functions which will give exact result when the same arguments are passed. • For example the mathematical function sin (0) always results 0. •
- 17. Pure functions • strlen (s) is called each time and strlen needs to iterate over the whole of ‘s’. • Evaluation of pure functions does not cause any side effects to its output
- 18. Impure functions • The variables used inside the function may cause side effects though the functions which are not passed with any arguments. In such cases the function is called impure function. • For example the mathematical function random() will give different outputs for the same function call.
- 20. Chameleons of Chromeland problem using function • monochromatize (a, b, c) 6