%-------------------------------------%
% Lab 2 : MATLAB Statements           %
% Date: 9/10/2002                     %
%                                     %
% Gun Srijuntongsiri                  %
% gs61                                %
% ??????                              %
%-------------------------------------%


%------------------------------------------------------------------------------
% CS99 Lab 2
% 9/10/2002
% MATLAB Statements
%------------------------------------------------------------------------------
% (0) Read these objectives of today's lab:
%
%     + practice with MATLAB tokens (see matlabtokens.txt)
%     + learn about general MATLAB statements
%     + learn about input/output (I/O) statements
%------------------------------------------------------------------------------
% (1) What to hand in:
%
%     + Create a file called lab2.m.
%     + Write a comment block in the required format at the top
%       (see Syllabus)
%     + Complete the *entire* document in your file.
%     + Run each command in the command window to learn about it's behavior.
%       - for commands that are deliberate errors, comment out the 
%         erroneous command after testing it
%     + When you're done, this file will be a runnable MATLAB file!
%     + Due: submit by e-mail to Gun no later than noon on Fri 9/13.
%
% Handy things to set up!

  clear all % clear all variable assignments
  more off   % turn off pager
  clc       % clear screen

%------------------------------------------------------------------------------
% (2) Statements
%
% Tasks:
%
% Complete these comments and write inside lab2.m:
%
%   A written language uses an __alphabet__ to create its words.
%   A computer language uses a __character__ for its words.
%   A computer language's "words" are really called __tokens__ .
%   To communicate in a written language, you combine words to
%      form __sentences__. These __sentences__ are called
%      __statements__ in a computer language.
%   Each statement is essentially a command or instruction that you give
%   to the computer.
%------------------------------------------------------------------------------
% (3) Empty statements
%
% + An EMPTY STATEMENT is the simplest form of a command.
% + MATLAB automatically succeeds at an empty statement.
%
% Tasks: Show two examples (pressing Return and a semicolon):

  % Return:  

  
  % Semicolon:
  ;
  
%------------------------------------------------------------------------------
% (2) Expression
%
% + MATLAB evaluates all arithmetic/logic operations
% + MATLAB reports the result as output
% + The result us automatically stored in variable $ans$ if you do not 
%   specify something else
% + You can suppress output with semicolon (;)
% + Want list of arithmetic operators? see $help arith$
% + Want list of logic operators? see $help relop$
%
% Tasks:

  % Add 1 and 1 and show output:
  1+1

  % Multiply 1 and 2 and suppress output: 
  1*2;

% + operator precedence:
%    - some operators come before others:
%      1+2*3 means 1+(2*3) automatically
%    - can change behavior with parentheses
%      (1+2)*3 means just that!
% + operator associativity
%    - operators have a "direction" when confronting themselves....
%      1-2-3 means (1-2)-3 because minus associates left
%
% Tasks:


  % Show how 1/(2+3) differs from 1+2/3:
  1/(2+3)
  1+2/3

    % alternatively,
    1/(2+3)==1+2/3    % will output 1 if equal, 0 if not.


  % Show how 1*(2*3) is identical to (1*2)*3:
  1*(2*3)
  (1*2)*3
  
    % alternatively,
    1*(2*3)==(1*2)*3  % will output 1 if equal, 0 if not.


%------------------------------------------------------------------------------
% (3) Declaration
%
%     + in other languages, need to tell MATLAB about the data types
%     + MATLAB is weakly typed!
%     + everything is an array 
%       - will demonstrate later...
%       - if curious, try this: x = 11:15, x(3), x + 1, x(1:5) + 1
% 
% Tasks:


  % Show how entering an unassigned variable causes an error:
  % k

%------------------------------------------------------------------------------
% (4) Assignment
%
%     + you *will* want to reuse values
%     + store results of expressions in variables
%     + syntax: $var=value$
%     + think in terms of "variable gets value"
%       or pseudocode: variable<-value
%     + to see a variable's value, enter variable at the prompt
%     + cannot use a variable until it's assigned
%     + variables assigned in the command window are GLOBAL
%       (known until you reassign or clear)
%     + examples)
%       clear   % removes all assignments
%       x       % causes an error because x is not assigned yet
%       y+1     % same problem: y isn't assigned yet!
%       x = 1   % x gets the value 1
%       x+2     % MATLAB knows that x means 1, so x+1 produces 3
%       clear x % remove the value in x
%       x       % uh oh: cannot use x now because value is removed
%
% Tasks:


  % Assign the value 10 to variable y:
  y = 10;
 
  % Clear variable y:
  clear y

  % Demonstrate the variable y is cleared:
  % y    % which yields "Undefined..." error.

    % alternatively,
    who     % lists all existing variables. So you shouldn't see y in the list
    % or,
    who y   % lists all variables named y, which are none in this case.

 
  % Clear all variables:
  clear

  % Demonstrate "weakly typed" by assigning a string, an integer,
  % a floating-point number, and an array to the variable x: 
  x = 'cs99'
  x = 12
  x = 3.14
  x = [1 3 5 6 -2]


%------------------------------------------------------------------------------
% (5) Function call
%
%     + exectute a programmed procedure
%     + functions are M-Files that you can "pass" values
%       - you may access builtin functions or write your own!
%       - good for commonly needed evaluations
%     + syntax: name(arguments)
%       - name is the name of the function
%       - arguments are values that you pass to the function
%       - sometimes functions have no arguments
%         (and thus do not need the parentheses)
%     + examples)
%
%       sqrt(4)
%       rand
%
%     + some functions generate values called RETURN VALUES
%     + the return values replace the function's value in the expression
%     + example)
%
%       x = 1 + sqrt(4)   % produces 3
%
% Tasks:

  % Find the square root of 10 and multiply the result by 2:
  sqrt(10)*2
  
  % Generate a random number:
  rand


  % Find the square root of a randomly generated number. Hint: NEST your
  % functions by making the result one function the input of the other:
  sqrt(rand)


  % Find the floor (integer portion) of the number 7.7. Hint: See $help floor$:
  floor(7.7)

  % Find the floor of a randomly generated number:
  floor(rand)


  % Find a random number between 1 and 10:
  rand*9+1


  % Find a random INTEGER between 0 and 2:
  floor(rand*3)      % say x = rand*3. So if x is in (0,1), floor(x)=0,
                     %                    if x is in (1,2), floor(x)=1,
                     %                    if x is in (2,3), floor(x)=2.

 
  % Find a random INTEGER between 1 and 2:
  floor(rand*2)+1
 

  % Find a random INTEGER between two integers (MIN and MAX). Give MIN and
  % MAX initial values to test your code:
  min = -4
  max = 12
  floor(rand*(max-min+1)+min)    % Note that min is inside floor, to correct
                                 %   cases when min < 0.


%------------------------------------------------------------------------------
% (6) I/O statements (examples of functions)
%
% + input:
%   - keyboard: the program prompts the user
%   - file: the program "sucks in" a file with needed information
% + output:
%   - keyboard, file, printer, etc...
%
% Simple input:
% + see $help input$
% + example session:
%
%    >> input('Enter anything: ')
%    Enter anything: 3
%    ans =
%          3
%
% Notes on $input$:
% + $input$ requires a value!
% + a correctly entered value is stored in special variable $ans$
%   ($ans$ is most recently entered value)
% + To store the result of an input, use an assignment with this syntax:
%   var = input('message: ');
%
% Tasks:


  % Prompt the user to enter their name as a string:
  input('What is your name? ','s');

  % Prompt the user to enter their age:
  input('How old are you? ');

  % Prompt the user to enter their age and store the result in variable $age$:
  age = input('How old are you? ');

% Simple output:
% + see $help disp$
% + $disp$ requires a single string or array of strings 
%   - an array is a collection of values
%   - for now, use syntax [element,element,element,...]
%   - example) x = ['s','abc','qwerty']
%   - to print a number with $disp$, you need to convert it to a string
%     with $num2str$
%   - example) x = 1; disp(num2str(x));
%
% + $disp$ examples:
%
%   >> disp('hi!')
%   >> x = 1; disp(['The value of x is: ',num2str(x)]
%
% Tasks:


  % Prompt the user for their favorite color and output the result:
  color = input('What is your favorite color? ','s');
  disp(['Your favorite color is ',color,'.']);


  % Prompt the user for their age and output the result in this format:
  % Your age is 82.
  age = input('How old are you? ');
  disp(['Your age is ', num2str(age), '.']);


% Done!
%------------------------------------------------------------------------------