They're making a connection between non-jumping code with a list, and jumping code, like classes, functions, etc. with a graph. A list can be iterated from beginning to end and read in sequence, or can be jumped into at any point in the code at arbitrary points. Similarly, if I open a file and want to read code, I can jump to any arbitrary line in the code and go forwards or backwards to see what the sequence of code is like. I can guarantee that line n happens before line n+1.
With functions, classes, modules, whatever, the actual code is located somewhere else. So for me to understand what the program is doing I have to trust that the function is doing what it says it's doing, or "jump" in the code to that section. My sequence is broken. Furthermore, because I am now physically in a new part of the code, my own internal "cache" is insufficient. It takes me some effort to understand this new piece of code and re-initialize the cache in my mind.
The overall thrust of DRY is overrated is that we often times take DRY too literally. If I have repeated myself I MUST find a way to remove that repetition; this typically means writing a function. Whereas previously the code could be read top to bottom now I must make a jump to somewhere else to understand it. The question isn't whether this is valuable, rather, whether it is overused.
They're making a connection between non-jumping code with a list, and jumping code, like classes, functions, etc. with a graph. A list can be iterated from beginning to end and read in sequence, or can be jumped into at any point in the code at arbitrary points. Similarly, if I open a file and want to read code, I can jump to any arbitrary line in the code and go forwards or backwards to see what the sequence of code is like. I can guarantee that line n happens before line n+1.
With functions, classes, modules, whatever, the actual code is located somewhere else. So for me to understand what the program is doing I have to trust that the function is doing what it says it's doing, or "jump" in the code to that section. My sequence is broken. Furthermore, because I am now physically in a new part of the code, my own internal "cache" is insufficient. It takes me some effort to understand this new piece of code and re-initialize the cache in my mind.
The overall thrust of DRY is overrated is that we often times take DRY too literally. If I have repeated myself I MUST find a way to remove that repetition; this typically means writing a function. Whereas previously the code could be read top to bottom now I must make a jump to somewhere else to understand it. The question isn't whether this is valuable, rather, whether it is overused.