错误:Haskell中的非穷尽模式 [英] Error: Non-exhaustive patterns in Haskell
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问题描述
N
或 B
。我想为每一行代表矩阵,数量为 N
s。例如: [[B,B,N],[N,N,N]]
由 [1,3]
这是我的代码:
data Case = B | N导出(Show,Eq)
type Grille = [[Case]]
g0,g1 :: Grille
g0 = [[B,B,B, B,B,B,N],[B,B,N,B,N,B,B],[N,B,N,N,N,N,N],[B,B,B,N, N,B,N],[N,N,N,B,B,B,B],[B,B,B,N,N,B,N]]
g1 = [[B,B ,B,B,B,B,B],[B,B,N,N,N,B,B],[B,B,N,N,N,N,N],[B,B,B ,N,N,N,N],[N,N,N,B,B,B,B],[B,B,B,N,B,B,B]]
projH ::格栅 - > [Int]
projH [[]] = []
projH(x:xg)= testCase(x)++ projH(xg)
testCase :: [Case] - > [int] dans une ligne
testCase [] = [0]
testCase(x:xs)
| x == N = [head(testCase(xs))+ 1]
|否则= testCase(xs)
问题出在函数 projH
,我显然缺少一个模式,但是我使用
来处理
函数和 [[],...]
testCase [[]]
case。我不知道为什么会给我这个错误:
*主> projH g0
[1,2,6,3,3,3 ***例外:devoir.hs:(17,1) - (18,39):函数中的非穷尽模式projH
解决方案
projH [] = []
而不是您的
projH [[]] = []
通过分配 x = []
和 xg = []
由另一个语句处理
I have some code that deals with a list of lists (that represents a matrix). Each cell is an N
or a B
. I want to represent the matrix with the number of N
s for each line. For example: [[B,B,N],[N,N,N]]
is represented by [1,3]
.
Here's my code:
data Case = B|N deriving (Show, Eq)
type Grille =[[Case]]
g0,g1 :: Grille
g0 = [[B,B,B,B,B,B,N],[B,B,N,B,N,B,B],[N,B,N,N,N,N,N],[B,B,B,N,N,B,N],[N,N,N,B,B,B,B],[B,B,B,N,N,B,N]]
g1 = [[B,B,B,B,B,B,B],[B,B,N,N,N,B,B],[B,B,N,N,N,N,N],[B,B,B,N,N,N,N],[N,N,N,B,B,B,B],[B,B,B,N,B,B,B]]
projH :: Grille -> [Int]
projH [[]] = []
projH (x:xg) = testCase(x) ++ projH(xg)
testCase :: [Case] -> [Int]dans une ligne
testCase [] = [0]
testCase (x:xs)
| x == N = [head(testCase(xs))+1]
| otherwise = testCase(xs)
The problem is in the function projH
, I'm obviously missing a pattern, but I do handle the case with [[],...]
with the testCase
function and the [[]]
case. I don't know why it throws me this error:
*Main> projH g0
[1,2,6,3,3,3*** Exception: devoir.hs:(17,1)-(18,39): Non-exhaustive patterns in function projH
解决方案
projH [] = []
instead of your
projH [[]] = []
As the case you wrote is already handled by the other statement by assigning x = []
and xg = []
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