我开始hmatrix在 Haskell 中进行矩阵操作。我发现创建矩阵非常容易：
ghci> let m = (10><10) [1..]
ghci> m
(10><10)
[ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0
, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 17.0, 18.0, 19.0, 20.0
, 21.0, 22.0, 23.0, 24.0, 25.0, 26.0, 27.0, 28.0, 29.0, 30.0
, 31.0, 32.0, 33.0, 34.0, 35.0, 36.0, 37.0, 38.0, 39.0, 40.0
, 41.0, 42.0, 43.0, 44.0, 45.0, 46.0, 47.0, 48.0, 49.0, 50.0
, 51.0, 52.0, 53.0, 54.0, 55.0, 56.0, 57.0, 58.0, 59.0, 60.0
, 61.0, 62.0, 63.0, 64.0, 65.0, 66.0, 67.0, 68.0, 69.0, 70.0
, 71.0, 72.0, 73.0, 74.0, 75.0, 76.0, 77.0, 78.0, 79.0, 80.0
, 81.0, 82.0, 83.0, 84.0, 85.0, 86.0, 87.0, 88.0, 89.0, 90.0
, 91.0, 92.0, 93.0, 94.0, 95.0, 96.0, 97.0, 98.0, 99.0, 100.0 ]
这很容易，即使是矩阵乘法：
ghci> m <> m
(10><10)
[ 3355.0, 3410.0, 3465.0, 3520.0, 3575.0, 3630.0, 3685.0, 3740.0, 3795.0, 3850.0
, 7955.0, 8110.0, 8265.0, 8420.0, 8575.0, 8730.0, 8885.0, 9040.0, 9195.0, 9350.0
, 12555.0, 12810.0, 13065.0, 13320.0, 13575.0, 13830.0, 14085.0, 14340.0, 14595.0, 14850.0
, 17155.0, 17510.0, 17865.0, 18220.0, 18575.0, 18930.0, 19285.0, 19640.0, 19995.0, 20350.0
, 21755.0, 22210.0, 22665.0, 23120.0, 23575.0, 24030.0, 24485.0, 24940.0, 25395.0, 25850.0
, 26355.0, 26910.0, 27465.0, 28020.0, 28575.0, 29130.0, 29685.0, 30240.0, 30795.0, 31350.0
, 30955.0, 31610.0, 32265.0, 32920.0, 33575.0, 34230.0, 34885.0, 35540.0, 36195.0, 36850.0
, 35555.0, 36310.0, 37065.0, 37820.0, 38575.0, 39330.0, 40085.0, 40840.0, 41595.0, 42350.0
, 40155.0, 41010.0, 41865.0, 42720.0, 43575.0, 44430.0, 45285.0, 46140.0, 46995.0, 47850.0
, 44755.0, 45710.0, 46665.0, 47620.0, 48575.0, 49530.0, 50485.0, 51440.0, 52395.0, 53350.0 ]
但是我如何访问一个元素？例如，我想阅读m[10][10]，但我真的不知道该怎么做。
ghci> m[10][10]
<interactive>:30:1:
The function `m' is applied to two arguments,
but its type `Matrix Double' has none
In the expression: m [10] [10]
In an equation for `it': it = m [10] [10]