6.001 Structure and Interpretation of Computer Programs. Copyright o 2004 by Massachusetts Institute of Technology Slide 30.1.3 So what problem domain should we use? Well, we are going to target-the art of M. C. Escher create a language that describes pictures such as this famous one by m.C. Escher, called"quadratlimit"or"square limit". Not only will our language let us describe the process by which such pictures can be created, it will also let us create our own variations on this theme, leading to pictures that have a resemblance to the kind of elegant structure shown here in this Escher print 8m00 Slide 30.1. 4 So how do we describe such a system? Well, let's start with a simpler example. Here is a picture of my friend George. At an abstract level. what kinds of things would i like to do with George? 6001 SICP Slide 30.1.5 First, I might like to flip him, either about the vertical axis or about the horizontal one. By this I mean literally taking this portrait of George and spinning it 180 degrees out of the plane, then setting it back down 4 87/2003 6m13P Slide 30.1.6 V/ Alternatively, I might like to rotate him about an axis coming out the picture, causing him to do a cartwheel as I rotate his picture by increments of 90 degrees. Conceptually this is easy If I think of George as a picture, I can easily envision grabbi the whole picture and doing something to it. But how do i do this in practice? 6001S1CP6.001 Structure and Interpretation of Computer Programs. Copyright © 2004 by Massachusetts Institute of Technology. Slide 30.1.3 So what problem domain should we use? Well, we are going to create a language that describes pictures such as this famous one by M.C. Escher, called "quadratlimit" or "square limit". Not only will our language let us describe the process by which such pictures can be created, it will also let us create our own variations on this theme, leading to pictures that have a resemblance to the kind of elegant structure shown here in this Escher print. Slide 30.1.4 So how do we describe such a system? Well, let's start with a simpler example. Here is a picture of my friend George. At an abstract level, what kinds of things would I like to do with George? Slide 30.1.5 First, I might like to flip him, either about the vertical axis or about the horizontal one. By this I mean literally taking this portrait of George and spinning it 180 degrees out of the plane, then setting it back down. Slide 30.1.6 Alternatively, I might like to rotate him about an axis coming out the picture, causing him to do a cartwheel as I rotate his picture by increments of 90 degrees. Conceptually this is easy. If I think of George as a picture, I can easily envision grabbing the whole picture and doing something to it. But how do I do this in practice?