1. Pages 61-68 Section: Control2: Repetition

2. Introduction Three major types of language constructs or statements:
Sequential statement
Decision/selection statement
Repetition/iteration statement
Iterative statements
Are used to compact length lines of repetitive code
Expresses concisely a repetitive operation
We will learn “for” statement of Processing

3. Examples
line(20, 20, 20, 180); line(30, 20, 30, 180); line(40, 20, 40, 180); line(50, 20, 50, 180); line(60, 20, 60, 180); line(70, 20, 70, 180); line(80, 20, 80, 180); line(90, 20, 90, 180); line(100, 20, 100, 180);
for (i = 20; i< 120; i= i+ 10) { line(i,20,i,180); }

4. For syntax and semantics
for (init; test; update) {
statements }
The init statement is executed
The test is evaluated to true or false
If the test is true, execute the statement within the block indicated by { }
If the test is false skip to the statement after the “for” statement

5. More examples
for (int x = -16; x <100; x = x + 10) { line(x,0,x+15, 50); } strokeWeight(4); for (int x = -8; x , 100; x = x + 10) { line (x,50,x+15, 100); }

6. More Examples
noFill(); for (int d = 150; d > 0; d = d -10) { ellipse (50, 50, d, d); } Try some of the examples in page 64

7. Nested Iteration
A “for” statement produces repetition in one dimension.
Nesting a “for” within a “for” generates “looping” in 2 dimensions.
Lets look at some examples.

8. Nested Loops
strokeWeight(4); for (int y = 10; y <100; y = y+10) // dimension y point(10,y); for (int x = 10; x <100; x = x+10) // dimensión x point(x,10); //nested for .. Two dimensions point(x,y);

9. More Examples
noStroke(); for (int y = 10; y <100; y = y+10) // dimension y for (int x = 10; x <100; x = x+10) // dimensión x { fill((x+y)*1.4); rect(x,y,10,10); }

10. Summary
We studied the syntax, semantics and purpose of “for” statement
We also looked at many examples
Make sure you format the statements for readability, esp. now that we are adding complex statements to your code.