CS99, Fall 2002
Mon 11/11
Lecture 11
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(0) Announcements
    + Prelim 2 on 11/19
    + Final project ("Bahggle")
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(1) Overview

    + programming language
      - words/tokens
        + data types
	+ data structures
      - sentences/statements
        + selection	
        + repetition
        + others?

    + functions
      - justification
      - syntax
      - how/when to use
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(1) Case study: rolldice1.m

    + strengths?



    + weaknesses?



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(2) Improved case study: rolldice2.m

    + strengths?


    + weaknesses?


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(3) Justification of functions

    + goal: 
      - modular programs (small chunks)
      - develop "black boxes" to perform repetitive tasks

    + good style:
      - clarity -- avoids "spaghetti code"
      - reduced redundancy in code

    + debugging and development
      - iterative refinement
      - testing by parts

    + code reuse:
      - reduced redundancy in *time* to program
      - can share code

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(4) Current Approach: Script M-files

    + definition of SCRIPT:
      - the M-files you've written so far
      - collection of commands that you could have entered at the prompt
      - see scripthelp.txt online

    + approach: 
      - write "little" subprograms
      - store them in different m-files
      - call the programs when necessary, but ensure path is set
      - invoke by using the script name as a command
      - use EVAL: ex) >> eval('scriptname')

    + visibility of variables (called SCOPE)
      - all scripts share vars of other scripts
      - called GLOBAL VISIBILITY

ex) 

    restore.m        s1.m              s2.m  
    +--------+ 	    +----------+      +--------+ 
    | clear  | 	    | restore  |      | s1;    | 
    | clc    | 	    | x=1;     |      | x=x+1; | 
    +--------+ 	    | pause    |      +--------+ 
                    +----------+

    >> s2; x; restore

    Output?











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(5) New Approach: Function M-files

    + math definition:
      - correspondance of two sets
      - given input of value from one set produces a value from the other set

        ex) square root of 4
            input:  4, which belongs to set of real numbers
            output: 2, which belongs to set of real numbers

    + programming definition:
      - the gist: sequence of steps to do task
      - name(inputs): given inputs, get output(s)

        ex) >> 1 + sqrt(4)
            >> randInt(0,1)
            >> x = input('enter something')
    
      - functions can be math or task!
      - *MATLAB* functions can zero-many inputs and zero-many outputs
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