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The edge iterator, and the dense walks of GridIterator and GridIntoIterator, step x along a row and move to the next row when x comes back to width. With a width of zero x never does, so y never advances and the walk never ends. A grid without columns has no vertices, so all three now yield nothing. Fixes evenfurther#842
| if self.y == self.grid.height { | ||
| // With no columns, `x` would never come back to `width` and the walk would | ||
| // never move on to the next row. | ||
| if self.y == self.grid.height || self.grid.width == 0 { |
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Isn't it a bit strange to redo the self.grid.width == 0 at every iteration of the loop instead of once at the beginning?
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Fixes #842.
Iterating a
Gridwithout columns never returned:Grid::new(0, 5).edges()in any state, anditer()/into_iter()once such a grid is dense, for instance afterfill()or after shrinking a full grid withresize(0, h).All three walks step
xalong a row and move to the next row whenxcomes back towidth. With a width of zero that never happens, soynever advances and they == heightexit is never reached. They now stop straight away when there are no columns, since such a grid has no vertices and no edges.Test
a_grid_without_columns_iterates_to_nothingintests/grid.rscoversedges(),iter()andinto_iter(), both onGrid::new(0, 5)afterfill()and on a full 3x3 grid shrunk to 0x3, and checksvertices_len()along the way. It hangs on currentmainand passes with this change.I also checked the rest of
Gridagainst a plain set of vertices through a few thousand randomadd_vertex,remove_vertex,add_borders,resize,fillandclearoperations, in both diagonal modes, comparing vertices, edges and neighbours after each step. Everything else agreed, so this is limited to the zero-width case.