lunduniversity / introprog

Teaching material for "Introduction to Programming using Scala" at Lund University, LTH. http://cs.lth.se/pgk/
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w04 exercise 7c: incorrect solution in answer key #667

Closed snctfd closed 2 years ago

snctfd commented 2 years ago

The exercise description for w04 exercise 7c asks the student to draw a square with its upper left corner at (100, 100). It gives the following code as a start:

1 > curl -sLO https://fileadmin.cs.lth.se/introprog.jar
2 > scala -cp introprog.jar
3 scala> val w = new introprog.PixelWindow(400,300,"HEJ")
4 scala> w.line(100, 100, 200, 100)
5 scala> w.line(200, 100, 200, 200)
6 scala> // fortsätt så att en hel kvadrat ritas

This seems correct, however the answer key ("facit") lists the following solution:

1 > scala -cp introprog_3-1.2.0.jar -repl
2 scala> val w = new introprog.PixelWindow(400,300,"HEJ")
3 scala> w.moveTo(100, 100)
4 scala> w.lineTo(200, 100)
5 scala> w.lineTo(200, 200)
6 scala> w.lineTo(100, 200)
7 scala> w.lineTo(100, 100)

Which uses functions that don't actually exist in the PixelWindow API, leading to errors and thus great confusion and sadness. The functions used seem to possibly be assuming a "turtle" style drawing, like in Kojo?