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No instance for (Fractional [Double]) arising from the literal ‘1.0’

Correct usage of the do notationPolyvariadic generalised sumFunction definition problems (No instance for … arising from)Haskell Location Definition “No instance for (Fractional Int) arising from a use of ‘/’”No instance for (Fractional ((Numerator, Denominator) -> Fraction a0 b0))Substitute n in [x|x<-[1..n]]No instance for (Integral Double) arising from a use of 'rem'Haskell No instance for (Fractional a0) arisingHow to convert from Int to Double?Haskell - No instance for (Eq (Int -> Int)) arising from a use of ‘==’

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0

For class, we have to write some code for a given set of problems. One of these problems is to create an identity matrix in the form of a [[Double]] So far, I have come up with the following code. However, when I try to compile I get the following error, not sure of what I did wrong or what it means

CODE:

ident :: Int -> [[Double]]
ident x = identHelper x 0

identHelper :: Int -> Int -> [[Double]]
identHelper y z
 | z == 0 = ([1.0] ++ replicate (y-1) 0.0) : identHelper y 1
 | y == z = replicate (y-1) 0.0 : 1.0
 | otherwise = (replicate z 0.0 ++ [1.0] ++ replicate (y-z-1) 0.0) : identHelper y (z+1)

ERROR:

 • No instance for (Fractional [[Double]])
 arising from the literal ‘1.0’
 • In the second argument of ‘(:)’, namely ‘1.0’
 In the expression: replicate (y - 1) 0.0 : 1.0
 In an equation for ‘identHelper’:
 identHelper y z
 | z == 0 = ([1.0] ++ replicate (y - 1) 0.0) : identHelper y 1
 | y == z = replicate (y - 1) 0.0 : 1.0
 | otherwise
 = (replicate z 0.0 ++ [1.0] ++ replicate (y - z - 1) 0.0)
 : identHelper y (z + 1)

haskell

share|improve this question

edited Apr 12 at 1:23

Michael Litchard

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asked Mar 28 at 20:40

Yogesh PatelYogesh Patel

644 bronze badges

add a comment
 | 

0

For class, we have to write some code for a given set of problems. One of these problems is to create an identity matrix in the form of a [[Double]] So far, I have come up with the following code. However, when I try to compile I get the following error, not sure of what I did wrong or what it means

CODE:

ident :: Int -> [[Double]]
ident x = identHelper x 0

identHelper :: Int -> Int -> [[Double]]
identHelper y z
 | z == 0 = ([1.0] ++ replicate (y-1) 0.0) : identHelper y 1
 | y == z = replicate (y-1) 0.0 : 1.0
 | otherwise = (replicate z 0.0 ++ [1.0] ++ replicate (y-z-1) 0.0) : identHelper y (z+1)

ERROR:

 • No instance for (Fractional [[Double]])
 arising from the literal ‘1.0’
 • In the second argument of ‘(:)’, namely ‘1.0’
 In the expression: replicate (y - 1) 0.0 : 1.0
 In an equation for ‘identHelper’:
 identHelper y z
 | z == 0 = ([1.0] ++ replicate (y - 1) 0.0) : identHelper y 1
 | y == z = replicate (y - 1) 0.0 : 1.0
 | otherwise
 = (replicate z 0.0 ++ [1.0] ++ replicate (y - z - 1) 0.0)
 : identHelper y (z + 1)

haskell

share|improve this question

edited Apr 12 at 1:23

Michael Litchard

2,00122 gold badges1919 silver badges4444 bronze badges

asked Mar 28 at 20:40

Yogesh PatelYogesh Patel

644 bronze badges

add a comment
 | 

For class, we have to write some code for a given set of problems. One of these problems is to create an identity matrix in the form of a [[Double]] So far, I have come up with the following code. However, when I try to compile I get the following error, not sure of what I did wrong or what it means

CODE:

ident :: Int -> [[Double]]
ident x = identHelper x 0

identHelper :: Int -> Int -> [[Double]]
identHelper y z
 | z == 0 = ([1.0] ++ replicate (y-1) 0.0) : identHelper y 1
 | y == z = replicate (y-1) 0.0 : 1.0
 | otherwise = (replicate z 0.0 ++ [1.0] ++ replicate (y-z-1) 0.0) : identHelper y (z+1)

ERROR:

 • No instance for (Fractional [[Double]])
 arising from the literal ‘1.0’
 • In the second argument of ‘(:)’, namely ‘1.0’
 In the expression: replicate (y - 1) 0.0 : 1.0
 In an equation for ‘identHelper’:
 identHelper y z
 | z == 0 = ([1.0] ++ replicate (y - 1) 0.0) : identHelper y 1
 | y == z = replicate (y - 1) 0.0 : 1.0
 | otherwise
 = (replicate z 0.0 ++ [1.0] ++ replicate (y - z - 1) 0.0)
 : identHelper y (z + 1)

haskell

share|improve this question

edited Apr 12 at 1:23

Michael Litchard

2,00122 gold badges1919 silver badges4444 bronze badges

asked Mar 28 at 20:40

Yogesh PatelYogesh Patel

644 bronze badges

ident :: Int -> [[Double]]
ident x = identHelper x 0

identHelper :: Int -> Int -> [[Double]]
identHelper y z
 | z == 0 = ([1.0] ++ replicate (y-1) 0.0) : identHelper y 1
 | y == z = replicate (y-1) 0.0 : 1.0
 | otherwise = (replicate z 0.0 ++ [1.0] ++ replicate (y-z-1) 0.0) : identHelper y (z+1)

 • No instance for (Fractional [[Double]])
 arising from the literal ‘1.0’
 • In the second argument of ‘(:)’, namely ‘1.0’
 In the expression: replicate (y - 1) 0.0 : 1.0
 In an equation for ‘identHelper’:
 identHelper y z
 | z == 0 = ([1.0] ++ replicate (y - 1) 0.0) : identHelper y 1
 | y == z = replicate (y - 1) 0.0 : 1.0
 | otherwise
 = (replicate z 0.0 ++ [1.0] ++ replicate (y - z - 1) 0.0)
 : identHelper y (z + 1)

share|improve this question

edited Apr 12 at 1:23

Michael Litchard

2,00122 gold badges1919 silver badges4444 bronze badges

asked Mar 28 at 20:40

Yogesh PatelYogesh Patel

644 bronze badges

share|improve this question

edited Apr 12 at 1:23

Michael Litchard

2,00122 gold badges1919 silver badges4444 bronze badges

asked Mar 28 at 20:40

Yogesh PatelYogesh Patel

644 bronze badges

edited Apr 12 at 1:23

Michael Litchard

2,00122 gold badges1919 silver badges4444 bronze badges

edited Apr 12 at 1:23

Michael Litchard

2,00122 gold badges1919 silver badges4444 bronze badges

asked Mar 28 at 20:40

Yogesh PatelYogesh Patel

644 bronze badges

asked Mar 28 at 20:40

Yogesh PatelYogesh Patel

644 bronze badges

1 Answer
1

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6

The problem is

 replicate (y-1) 0.0 : 1.0

BTW you can (and should) always leave away trailing zeroes, so

 replicate (y-1) 0 : 1

For example, say y=4. Then this reads

 [0,0,0] : 1

So you're trying to prepend the list [0,0,0] before the... list? 1. How is 1 supposed to be a list?

I'm not sure what you want there, but one plausible option is [[1]].

share|improve this answer

answered Mar 28 at 20:46

leftaroundaboutleftaroundabout

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6

The problem is

 replicate (y-1) 0.0 : 1.0

BTW you can (and should) always leave away trailing zeroes, so

 replicate (y-1) 0 : 1

For example, say y=4. Then this reads

 [0,0,0] : 1

So you're trying to prepend the list [0,0,0] before the... list? 1. How is 1 supposed to be a list?

I'm not sure what you want there, but one plausible option is [[1]].

share|improve this answer

answered Mar 28 at 20:46

leftaroundaboutleftaroundabout

83.6k33 gold badges125125 silver badges250250 bronze badges

add a comment
 | 

6

The problem is

 replicate (y-1) 0.0 : 1.0

BTW you can (and should) always leave away trailing zeroes, so

 replicate (y-1) 0 : 1

For example, say y=4. Then this reads

 [0,0,0] : 1

So you're trying to prepend the list [0,0,0] before the... list? 1. How is 1 supposed to be a list?

I'm not sure what you want there, but one plausible option is [[1]].

share|improve this answer

answered Mar 28 at 20:46

leftaroundaboutleftaroundabout

83.6k33 gold badges125125 silver badges250250 bronze badges

add a comment
 | 

The problem is

 replicate (y-1) 0.0 : 1.0

BTW you can (and should) always leave away trailing zeroes, so

 replicate (y-1) 0 : 1

For example, say y=4. Then this reads

 [0,0,0] : 1

So you're trying to prepend the list [0,0,0] before the... list? 1. How is 1 supposed to be a list?

I'm not sure what you want there, but one plausible option is [[1]].

share|improve this answer

answered Mar 28 at 20:46

leftaroundaboutleftaroundabout

83.6k33 gold badges125125 silver badges250250 bronze badges

 replicate (y-1) 0.0 : 1.0

 replicate (y-1) 0 : 1

 [0,0,0] : 1

share|improve this answer

answered Mar 28 at 20:46

leftaroundaboutleftaroundabout

83.6k33 gold badges125125 silver badges250250 bronze badges

answered Mar 28 at 20:46

leftaroundaboutleftaroundabout

83.6k33 gold badges125125 silver badges250250 bronze badges

answered Mar 28 at 20:46

leftaroundaboutleftaroundabout

83.6k33 gold badges125125 silver badges250250 bronze badges