resonate command #1204
resonate command #1204
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src/Swarm/Game/Value.hs
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| pattern VRect :: Integer -> Integer -> Integer -> Integer -> VRect | ||
| pattern VRect x1 y1 x2 y2 = VPair (VPair (VInt x1) (VInt y1)) (VPair (VInt x2) (VInt y2)) | ||
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| {-# COMPLETE VRect #-} |
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I don't think we want this COMPLETE pragma. The meaning of such a pragma would be that pattern-matching on VRect is sufficient to cover all possible Values, but that is certainly not true. And indeed, the rectCells function is in fact a partial function, and we don't want to just paper over that with a bogus COMPLETE pragma. We never want partial functions (even in cases where bad inputs "shouldn't ever happen"), since as a matter of policy/quality control we want to try to make sure that the game can not possibly crash.
src/Swarm/Game/Step.hs
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| @@ -1243,14 +1243,21 @@ execConst c vs s k = do | |||
| let Location x y = loc | |||
| return $ Out (VPair (VInt (fromIntegral x)) (VInt (fromIntegral y))) s k | |||
| Detect -> case vs of | |||
| [VText name, VPair (VPair (VInt x1) (VInt y1)) (VPair (VInt x2) (VInt y2))] -> do | |||
| [VText name, r] -> do | |||
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There is a subtle issue here, which is that this pattern now matches any Value as the second argument to Detect instead of only pairs of pairs of ints. In theory, if typechecking works, that is the only possible value we could ever get here. But in case there is ever any kind of bug that causes the wrong kind of Value to end up here, previously it would have fallen through to the badConst case, which throws an appropriate in-game exception; with the current code, it will instead actually crash the whole game with a non-exhaustive pattern match error in the rectCells function.
We should be using a VRect pattern here, in the pattern for vs, and then pass the resulting four Int values to rectCells. That way rectCells will be a total function.
Towards #1171
The
resonatecommand counts entities of a given type within a rectangle.This PR also fixes a bug in
detectwhen the rectangle coords are non-ascending.