>Autochrome and difftastic represent diffing as a shortest path problem on a directed acyclic graph. A vertex represents a pair of positions: the position in the left-hand side s-expression (before), and the position in the right-hand side s-expression (after).
>The goal is to find the shortest route from the start vertex (where both positions are before the first item in the programs) to the end vertex (where both positions are after the last item in the program).
I don't understand what this means at all? What is a "position" here? Position of what? If it's a graph, what do the edges represent? The diagrams afterwards aren't very helpful either, I can't make head nor tail of them. They talk about a "start" vertex and an "end" vertex, but before that it said that a vertex is a pair of start-end positions ... I'm totally lost.