[Haskell-beginners] help with lists and tuples

[Bob Ippolito]

It looks like you want this instead:

nActivationSum :: [(Float, Float)] -> [Float]
nActivationSum (xy : xys) = nActivation xy : nActivationSum xys
nActivationSum [] = []

This pattern is more commonly expressed with map like this:

nActivationSum :: [(Float, Float)] -> [Float]
nActivationSum inputsAndWeights = map nActivation inputsAndWeights

Or you could write it a bit shorter in point-free style:

nActivationSum :: [(Float, Float)] -> [Float]
nActivationSum = map nActivation



On Sun, Apr 14, 2013 at 4:04 PM, Miro Karpis <miroslav.karpis at gmail.com>wrote:

> Please can you help me with this? What I want is to have on input a list
> of tuple (size 2) and on output list of floats. So now I'm returning only
> float instead of a list. But unfortunately I can't figure out how to
> implement the list......
>
>
> sigmoid :: Float -> Float
> sigmoid x = 1.0 / (1 + exp (-x))
>
> nActivation :: (Float,Float) -> Float
> nActivation (x,y) = sigmoid(x*y)
>
> nActivationSum :: [(Float, Float)] -> [Float]
> nActivationSum [] = []
> nActivationSum (inputs:weights) = *nActivation* (inputs, weights)
>
>
>
> Couldn't match expected type `[Float]' with actual type `Float'
>     In the return type of a call of `nActivation'
>     In the expression: nActivation (inputs, weights)
>     In an equation for `nActivationSum':
>         nActivationSum (inputs : weights) = nActivation (inputs, weights)
>
>
> thanks,
> m.
>
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