Haskell hmatrix：vector/scalar 交互输入错误？

Question

我运行研究了标量和矩阵在 hmatrix 中表现奇怪的这些奇怪情况。如果我不输入 annotate，该操作会自动运行 matlab/python。但是，如果我使用 "R" 或类型或 "Double" 对标量进行类型注释，我会收到类型错误。

这是为什么？

λ> 4 +  ([1,2,3] :: Vector R) 
[5.0,6.0,7.0]
λ> (4 :: R) +  ([1,2,3] :: Vector R) 

<interactive>:155:14:
    Couldn't match type ‘Vector R’ with ‘Double’
    Expected type: R
      Actual type: Vector R
    In the second argument of ‘(+)’, namely ‘([1, 2, 3] :: Vector R)’
    In the expression: (4 :: R) + ([1, 2, 3] :: Vector R)
    In an equation for ‘it’: it = (4 :: R) + ([1, 2, 3] :: Vector R)
λ> (4 :: Double) +  ([1,2,3] :: Vector R) 

<interactive>:156:19:
    Couldn't match expected type ‘Double’ with actual type ‘Vector R’
    In the second argument of ‘(+)’, namely ‘([1, 2, 3] :: Vector R)’
    In the expression: (4 :: Double) + ([1, 2, 3] :: Vector R)
    In an equation for ‘it’:
        it = (4 :: Double) + ([1, 2, 3] :: Vector R)
λ> (4 :: R) *  ([1,2,3] :: Vector R) 

<interactive>:157:14:
    Couldn't match type ‘Vector R’ with ‘Double’
    Expected type: R
      Actual type: Vector R
    In the second argument of ‘(*)’, namely ‘([1, 2, 3] :: Vector R)’
    In the expression: (4 :: R) * ([1, 2, 3] :: Vector R)
    In an equation for ‘it’: it = (4 :: R) * ([1, 2, 3] :: Vector R)
λ> 4  *  ([1,2,3] :: Vector R) 
[4.0,8.0,12.0]
λ>

Answer 1

我认为它已记录在案 here

Autoconformable dimensions

In most operations, single-element vectors and matrices (created from numeric literals or using scalar), and matrices with just one row or column, automatically expand to match the dimensions of the other operand

您必须匹配类型和大小，但是您的注释类型是标量，期望第二个操作数中有向量。

Haskell hmatrix：vector/scalar 交互输入错误？

Haskell hmatrix: type errors with vector/scalar interactions?

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