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Conditionals

Conditionals. animation scripting. c sc 233. Conditionals. Variables Conditionals Boolean Expressions Conditional Statements How a program produces different results based on varying circumstances if, else if, else Boolean variables. What is a Boolean Expression?. AND.

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Conditionals

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  1. Conditionals animation scripting csc 233

  2. Conditionals • Variables • Conditionals • Boolean Expressions • Conditional Statements • How a program produces different results based on varying circumstances • if, else if, else • Boolean variables

  3. What is a Boolean Expression? AND • Something that resolves to either true or false (yes or no) • Not maybe… • Computers think in 1’s and 0’s • Remember truth tables • 1 = ON = True • 0 = OFF = False • Usually based on a comparison • Are you 21 years old? • Is changeCount less than 5? • Is myScore between 80 and 89? • Is lastName ‘Smith’? OR

  4. Boolean Comparison Operators • Similar to Algebra • > greater than • < less than • >= greater than or equal to • <= less than or equal to • == equality (equal to) • Note: ‘=‘ is the ‘assignment’ operator: x = 5; • != inequality (not equal to) Learning Processing: Slides by Don Smith

  5. Boolean Expressions and if • What is a Boolean Expression? • A comparison that results in either a true or a false • Where do I use it? • Usually in parenthesis, after an if: • if (age >= 21) • // True Action • if (mouseX < width/2) • // True Action • Only do ‘Action’ if condition is • True Condition True False Action

  6. Two-way conditionals: if else • Use elsefor ‘false’ actions after an iftest: • ‘Binds’ with the closest if: • if (age >= 21) • // True Action • else // age < 21 • // False Action • Take one of the two paths: • True or False • Good idea to use curly braces: • if (age >= 21){ • // True Action • } else { • // False Action • } Condition True False False Action True Action

  7. Multiple Actions2 options if else • What if I have more than one thing to do if true? • Make a ‘block’ of code after the if: • if (age >= 21) { • // True Action 1 • // True Action 2 • } else • // False Action • Indentation is for humans • if (age >= 21) • // True Action 1 • // True Action 2 • Without the curly braces: • Only the first statement after a conditional is executed • True Action 2 is executed no matter what age is! • And don’t forget to ‘match’ your curly braces! Condition True False False Action True Action 1 True Action 2

  8. Multiple-Way Branching: else if • What if you want more than two paths? • Use else if: • if (age >= 21) • // First True Action • else if (age > 18) • // Second True Action • else if (age > 5) • // Third True Action • Only one action done • Then go to the ‘bottom’ First Condition True First True Action False Second Condition True Second True Action False Third Condition True Third True Action False

  9. else if with elseat the end • Two ‘true’ paths and one ‘neither’ path? • Useelse if: • if (age >= 21) • // First True Action • else if (age > 18) • // Second True Action • else • // Both False Action True First Condition First True Action False True Second Condition Second True Action False Both False Action

  10. Try This: else if elseAn example of Multi-way Branching • Where the mouse is determines the background color void setup(){ size (500, 500); } void draw(){ if (mouseX < width/3){ background(255); } else if (mouseX < 2*width/3){ background(127); } else { background(0); } }

  11. Multi-way Branching: Be careful how you arrange tests. // vs 1. How will this evaluate? int x = 75; void setup() { // set up start if (x > 50) { println( x + " is greater than 50"); } else if (x > 25) { println( x + " is greater than 25"); } else { println( x + " is 25 or less"); } } // setup close // vs 2. How will this evaluate? int x = 75; void setup() { // set up start if (x > 25) { println( x + " is greater than 25"); } else if (x > 50) { println( x + " is greater than 50"); } else { println( x + " is 25 or less"); } } // setup close

  12. Try this:Gradebook Application • Determine the letter grade for a number 0-100 • 90 – 100: A • 80 – 89.999 B • 70 – 79.999 C • 60 – 69.999 D • Below 60: F • How would you plan/code a solution? • What would you test for first? • What second? • How many tests do you need?

  13. Numeric Range testing • You often have to determine if a number is in a specific range (min to max) • Example: Which range is a number in? • 0-25: Print “Young” • 26-50: Print “Mid-Age” • >50: Print “Mature” • How would you plan/code a solution? • What would you test for first? • What second? • Can this be done with only two tests?

  14. Try This:if else Examples float r = 150; // variables float g = 0; float b = 0; void setup() { size(200,200); } void draw() { background(r,g,b); stroke(255); // Line down center line(width/2, 0, width/2, height); if (mouseX > width/2) // If right r = r + 1; // more red else // Else left r = r - 1; // less red if (r > 255) // Range Check r r = 255; if (r < 0) // Range Check r r = 0; } else ‘binds’ with closest if You can useifwith no else clause!

  15. Range check with constrain( ) float r = 150; // variables float g = 0; float b = 0; void setup() { size(200,200); } void draw() { background(r,g,b); stroke(255); // Line down center line(width/2, 0, width/2, height); if (mouseX > width/2) // If right r = r + 1; // more red else // Else left r = r - 1; // less red r = constrain(r,0,255); // Range Check r }

  16. Three-way branching float r = 150; // variables float g = 0; float b = 0; void setup() { size(200,200); } void draw() { background(r,g,b); stroke(255); line(width * 2/3, 0, width * 2/3, height); line(width * 1/3, 0, width * 1/3, height); if (mouseX > (width * 2/3)){ // right 3rd r = r + 1; println("r = " + r);} else if (mouseX < (width * 1/3)){ // left 3rd r = r -1; println("r = " + r);} else{ // center 3rd ellipse(mouseX, mouseY, 30,30); println("r = " + r); } r = constrain(r,0,255); // Range Check r }

  17. Exercise: Move a rectangle… but stop! float x = 0; void setup() { size(200,200); } void draw() { background(255); fill(0); rect(x,100,20,20); x = x + 1; // Keep x in left half // Conditional version: // constrain version: }

  18. Logical Operators: AND • Sometimes two (or more) things need to be true before you want to do something • Example: • If age >= 16 AND permit == 1 • Print “OK to drive” • How do we spell ‘AND’? && • ‘Nested ifs:’ One if, compound condition int age = 17; int permit = 1; if (age >= 16) if (permit == 1) print(“OK to Drive”); else print(“Ride the bus”); else print(“Ride the bus”); int age = 17; int permit= 1; if (age >= 16 && permit == 1) print(“OK to Drive”); else print(“Ride the bus”); Remember: else ‘binds’ with closest if (without an else)

  19. Logical Operators: OR • Sometimes one of (two or more) things is enough to decide int age = 17; int permit = 1; if (age >= 18 || (age >= 16 && permit == 1)) print(“OK to Drive”); else print(“Ride the bus”);

  20. Logical Operators: OR • Sometimes one of (two or more) things is enough to decide • Example: • If age >= 18 OR (age >= 16 AND permit == 1) • Print “OK to drive” • How do we spell ‘OR’? || (two vertical bars) int age = 17; int permit = 1; if (age >= 18 || (age >= 16 && permit == 1)) print(“OK to Drive”); else print(“Ride the bus”); • Note the use of parenthesis to ‘connect’ the AND clause

  21. Exercise:Simple Rollover int x = 50; int y = 50; int w = 100; int h = 75; void setup() { size(200,200); } void draw() { background(255); stroke(255); // test if mouse is over the rectangle if ( mouseX.. && mouseY.. && ??? // Change the color of the rectangle rect(x,y,w,h); }

  22. Second half • Multiple Rollovers • Boolean Variables • A bouncing ball • Physics 101

  23. Try this:multiple roll overs • Steps: • Draw a white background • Draw horizontal and vertical lines down the center • If mouse is in top left, draw black rectangle in that quadrant • If mouse is in top right, draw black rectangle in that quadrant • If mouse is in bottom left, draw black rectangle in that quadrant • If mouse is in bottom right, draw black rectangle in that quadrant • But how can we tell which quadrant it is in? • Upper Left: x = 0 to 99, y = 0 to 99 • Upper right: x = 100 to 199, y = 0 to 99 • …

  24. boolean variables • You may want to ‘remember’ if something is true or false and store it in a variable • Then you can compare it to true or false • Example: • If age >= 16 AND permit == true • Print “OK to drive” int age = 17; boolean permit = true; if (age >= 16 && permit == true) print(“OK to Drive”); else print(“Ride the bus”);

  25. Try this:A Button as a switch This sketch will use a Boolean value as a variable which can then be used to act like a switch to activate or deactivate the movement of the object. New idea is “!” or not equal to. click = !click; This makes the value of click become its opposite. In this case it toggles back and forth from true to false each time the mouse button is pressed. try it out for yourself. // Declare variables boolean click = false; // assigns a value of false to boolean intcircleX = 0; intcircleY = 0; void setup() { size(200,200); } void draw() { background(100); stroke(255); fill(0); ellipse(circleX, circleY, 50, 50); // Move the circle only after a click if (click){ // if Boolean click is true (pressed) circleX = circleX + 1; // then add 1 to x and y pos. circleY = circleY + 1; println (circleX); }else{ // if click is not pressed do nothing circleX = circleX; circleY = circleY; } } void mousePressed() { // change the value of the Boolean to click = !click; // the opposite: if true then false, if false then true/ // Location of the mouse doesn’t matter }

  26. Try this : Modulation A bouncing ‘ball’ intcircleX = 0; int speed = 1; void setup() { size(200,200); smooth(); } void draw() { background(255); circleX = circleX + speed; if ( circleX > width || circleX < 0) speed = speed * -1; // reverse course // Display the circle at x location stroke(0); fill(175); ellipse(circleX, 100, 32, 32); } • Use a variable speed which can be positive or negative. • Change speed to negative if we bounce off the right edge. // What will this do? void mousePressed() { speed = speed + 1; }

  27. A note about debugging… intcircleX = 0; int speed = 1; void setup() { size(200,200); smooth(); } void draw() { background(255); circleX = circleX + speed; if ( circleX > width || circleX < 0) speed = speed * -1; // reverse course // Display the circle at x location stroke(0); fill(175); ellipse(circleX, 100, 32, 32); } • You can print the variable speed to see what it is doing. • Use println(speed)if you want one number per line. void mousePressed() { speed = speed + 1; println(speed); }

  28. Summary • Conditionals allow you to control the flow • if, else, else if allow many options • Boolean expressions are used inside if(… ) tests • Resolve to either true or false • Boolean expressions use comparison operators: • >, <, >=, <=, ==, != • Boolean variables can be set to true or false, and also used in conditional expressions • AND and OR (&& and ||) are used to combine conditionals • You can use print()and println()to help debug your programs while you are testing them

  29. Exercises • 1.) Take your project 1 design and add more functionality to it that applies these concepts. Create roll over actions, movement around the screen, conditions, mouse interactivity. Build on to your project with this new knowledge. • 2.) Create a mock web navigation that utilizes roll over functionality and conditional statements to reveal content, create animation or draw images to the screen. Look ahead at text to add text to the screen also look at how to import images to your canvas and create web links.

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