Changing code into a loop

James' question was concerned with how you might go about repeating the same block of code

    t.push()
    t.turn(turnAngle);
    t.up();
    t.go(1);
    t.down();
    t.push();
    t.turn(-9*pi/10)
    t.go(sin(pi/5)/sin(7*pi/10))
    t.pop();
    t.turn(9*pi/10);
    t.down();
    t.go(sin(pi/5)/sin(7*pi/10));
    t.pop();
    % increment the turn angle

five time with the only difference being the turnAngle.

Answer 1

[Geoff Hayes]

James - just use a local variable to store the turn angle, and update it on each iteration of the for loop. Try something like the following

t=Turtle();

turnAngle = pi/2;

for k=1:5  
    t.push()
    t.turn(turnAngle);
    t.up();
    t.go(1);
    t.down();
    t.push();
    t.turn(-9*pi/10)
    t.go(sin(pi/5)/sin(7*pi/10))
    t.pop();
    t.turn(9*pi/10);
    t.down();
    t.go(sin(pi/5)/sin(7*pi/10));
    t.pop();
    % increment the turn angle
    turnAngle = turnAngle + 2*pi/5;
end

[James Connor]

Thanks a lot. By the way what does the k=1:5 do? Is it because it's a 5 pointed star? would I changed this to k=n for a star that has n points?

[Geoff Hayes]

James - see for loop for details on the usage of a for loop. Since you have five blocks of repeating code, then k=1:5 just executes the block of code five times, setting the indexing variable k to 1, 2, 3, 4, and 5 on each iteration of the loop. Try using the MATLAB debugger and step through the code to see what is happening.