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General Computer Science for Engineers CISC 106 Lecture 03

General Computer Science for Engineers CISC 106 Lecture 03. Dr. John Cavazos Computer and Information Sciences 2/16/2009. Lecture Overview. More on Functions -    Overview -    Calling functions from another function M-files -    Scripts versus functions. Functions.

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General Computer Science for Engineers CISC 106 Lecture 03

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  1. General Computer Science for EngineersCISC 106Lecture 03 Dr. John Cavazos Computer and Information Sciences 2/16/2009

  2. Lecture Overview • More on Functions-    Overview -    Calling functions from another functionM-files-    Scripts versus functions

  3. Functions • Analogous to mathematical functions • f(x) = x + 1 • Independent of the other code • Each function is like a mini-program within the larger program itself • Key to breaking problems down

  4. Functions • In MATLAB, the first line of a function takes the following form: function <return value> = <name>(<arguments>)

  5. Functions cont. • The first line of a function: function <return value> = <name>(<arguments>) • The return value can be a number, a string, a matrix, etc. • Arguments • Can be a list of zero or more variables • Can also be numbers, strings, matrices

  6. Functions • Functions can call other functions • Your program is the main function, calling smaller functions to solve subproblems • Like in class on Friday: function outputValue = ringArea(rad_1, rad_2) outputValue = circleArea(rad_1) - circleArea(rad_2);

  7. Functions • In this class you will have to design programs to solve problems • These problems will be best solved (most easily and cleanly) by breaking down into smaller subproblems • The subproblems will be solved using functions • How big/small should a function be? • No more than one page or screen of text

  8. Problem Solving • Examples of big problems and how we might break them down • Scheduling (next slide) • Facebook • user login, ways to store user info, recommend friends • MP3 player • Store song lists, store playlists, import/export songs, shuffle play, repeat play, etc.

  9. Problem solving • Let’s think about some example problems and how we might break them down • How to automatically generate a schedule for an airline/business/school etc.

  10. Course Scheduling Software • What are inputs and outputs? • Inputs: Resources (teachers, students, office staff, classes ) • Output: Schedule of where and when everything and everyone needs to be

  11. Course Scheduling example • What functions might we need? • How many classrooms available? • How much demand is there for each room? • Course requirements? • Break it down even more?

  12. M-files • An m-file is also called a script file • Store commands in • Running a script file (m-file) • A function file • Special type of m-file • Contains a function name, arguments, etc., and implementation

  13. Scripts vs. functions • Functions have input and output parameters • Scripts cannot • Functions are more flexible • Function files have one function per file

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