Hello Processing - Vula

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An Introduction To Programming With Processing Logical Errors Logical errors are errors that do not cause the program to halt, crash or throw an error but will cause the program to act in an unexpected manner or produce unintended results. Logical errors can therefore be difficult to track down and rectify because the PDE does not indicate the specific location of an error. Keeping track of your data through documentation and organizing it into small manageable chunks can be one method of avoiding logical errors. If your program seems to have a logical error you might have to use the println() function to track the values you were hoping to have your program return to you. Display Window In our Hello World 1.0 program after pressing the Run button you will notice that a new smaller window was created. This is the Display Window and because Processing is a visually oriented language it automatically creates this window which you will usually use to draw to. The default Display window has dimensions 100 pixels in width by 100 pixels in height. Hello World Program 1.0 50
An Introduction To Programming With Processing Lets take a look at how we can control the Display window with the size() function. The size() function allows you to specify the dimensions of the Display window in pixels. You use the size() function by supplying two parameters to it, an x value which defines the horizontal dimension of the Display window and a y value which defines the vertical dimension of the Display window. Just like the println() function, parameters for the size() function are entered between the function's parenthesis. For example if we wanted the dimension of the Display window to be 640 pixels across by 480 pixels down we would type: size(640,480); Note that because we have just entered a statement telling Processing how big we want the Display window to be we must terminate this statement with a semicolon. You will also note that the two values 640 and 480 are separated with a comma. Do not try to separate values with a semi-colon because the statement is incomplete at that point and you are therefore attempting to terminate it prematurely. This will most commonly result in a syntax error or even worse in a logical error in some cases. Parenthesis following a function's name is usually reserved for parameters relating to the function and these parameters are most commonly separated by commas. This is pretty easy to remember because in English you generally list items by separating them with a comma in Processing and many other higher level languages you separate parameter values for a function with a comma. The two values 640 and 480 have been “listed” in this particular order because when Processing accepts parameters of dimensional type like x and y (in 2 dimensions) or x, y and z (in 3 dimensions) it will generally accept values in the order x first, y second and z third. This is with the exception of a trigonometric function called atan2() in which y is read first followed by x due to the special circumstances of how this function works. Add the second statement to your Hello World 1.0 program Below the first statement type the second statement so that your code reads: println("Hello World"); size(640,480); Hello World Program 1.0 51
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Hello Processing - Vula

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