Multivariate function composition

Let's consider the following:

f: Int -> Int -> Int -> Int

f a b c = a + b + c



g: Int -> Int

g x = x * 2

now, I'd like to create a composed function like

f(g(a), g(b), g(c))

how to use << and >> operators to achieve that? Is it even possible to compose multivariadic functions?

edited Nov 25 '18 at 20:16

asked Nov 22 '18 at 8:54

Oskar Szura

1,31552240

add a comment |

Let's consider the following:

f: Int -> Int -> Int -> Int

f a b c = a + b + c



g: Int -> Int

g x = x * 2

now, I'd like to create a composed function like

f(g(a), g(b), g(c))

how to use << and >> operators to achieve that? Is it even possible to compose multivariadic functions?

edited Nov 25 '18 at 20:16

asked Nov 22 '18 at 8:54

Oskar Szura

1,31552240

add a comment |

Let's consider the following:

f: Int -> Int -> Int -> Int

f a b c = a + b + c



g: Int -> Int

g x = x * 2

now, I'd like to create a composed function like

f(g(a), g(b), g(c))

how to use << and >> operators to achieve that? Is it even possible to compose multivariadic functions?

edited Nov 25 '18 at 20:16

asked Nov 22 '18 at 8:54

Oskar Szura

1,31552240

Let's consider the following:

f: Int -> Int -> Int -> Int

f a b c = a + b + c



g: Int -> Int

g x = x * 2

now, I'd like to create a composed function like

f(g(a), g(b), g(c))

how to use << and >> operators to achieve that? Is it even possible to compose multivariadic functions?

elm

edited Nov 25 '18 at 20:16

asked Nov 22 '18 at 8:54

Oskar Szura

1,31552240

edited Nov 25 '18 at 20:16

asked Nov 22 '18 at 8:54

Oskar Szura

1,31552240

edited Nov 25 '18 at 20:16

asked Nov 22 '18 at 8:54

Oskar Szura

1,31552240

asked Nov 22 '18 at 8:54

Oskar Szura

1,31552240

asked Nov 22 '18 at 8:54

Oskar Szura

1,31552240

add a comment |

2 Answers
2

active

oldest

votes

Multivariadic does not really exist in Elm. Best I can suggest is

f : Int -> Int -> Int -> Int

f a b c =

    [ a, b, c ] |> List.map ((<|) g) |> List.sum





g : Int -> Int

g x =

    x * 2

Note that you had an error in the type signature for g

answered Nov 22 '18 at 11:55

Simon H

12.8k74477

Corrected, good point - as every function is curried (as I understand). Thanks for the answer.

– Oskar Szura
Nov 25 '18 at 20:17

add a comment |

how to use << and >> operators to achieve that? Is it even possible to compose multivariadic functions?

Yes, easily:

h = flip flip g << ((<<) (<<)) << ((>>) g) << f << g

h is a <function> : number -> number -> number -> number, which is the same as h a b c = f (g a) (g b) (g c).

I think we don't need to dig deep in the correctness, since it's obvious that the version with arguments is much more readable.

answered Nov 22 '18 at 14:03

Igor Drozdov

12k52444

Note that flip was removed from elm/core in 0.19, so I'd be very hesitant to accept this as a proper solution! /s

– glennsl
Nov 22 '18 at 15:14

thanks for the note about flip. my point in the answer is that it's possible to compose the functions in order to achieve the desired result, but it makes no sense since the code becomes less readable than straight solution

– Igor Drozdov
Nov 22 '18 at 15:29

Yeah, I got that, and I'm actually pretty impressed you managed (and bothered) to figure it out. Hence the (easily missed) "/s" to indicate sarcasm on my end ;)

– glennsl
Nov 22 '18 at 15:42

So practically it's possible but there's no point of doing so... Thanks for the answer :).

– Oskar Szura
Nov 25 '18 at 20:16

add a comment |

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

Multivariadic does not really exist in Elm. Best I can suggest is

f : Int -> Int -> Int -> Int

f a b c =

    [ a, b, c ] |> List.map ((<|) g) |> List.sum





g : Int -> Int

g x =

    x * 2

Note that you had an error in the type signature for g

answered Nov 22 '18 at 11:55

Simon H

12.8k74477

Corrected, good point - as every function is curried (as I understand). Thanks for the answer.

– Oskar Szura
Nov 25 '18 at 20:17

add a comment |

Multivariadic does not really exist in Elm. Best I can suggest is

f : Int -> Int -> Int -> Int

f a b c =

    [ a, b, c ] |> List.map ((<|) g) |> List.sum





g : Int -> Int

g x =

    x * 2

Note that you had an error in the type signature for g

answered Nov 22 '18 at 11:55

Simon H

12.8k74477

Corrected, good point - as every function is curried (as I understand). Thanks for the answer.

– Oskar Szura
Nov 25 '18 at 20:17

add a comment |

Multivariadic does not really exist in Elm. Best I can suggest is

f : Int -> Int -> Int -> Int

f a b c =

    [ a, b, c ] |> List.map ((<|) g) |> List.sum





g : Int -> Int

g x =

    x * 2

Note that you had an error in the type signature for g

answered Nov 22 '18 at 11:55

Simon H

12.8k74477

Multivariadic does not really exist in Elm. Best I can suggest is

f : Int -> Int -> Int -> Int

f a b c =

    [ a, b, c ] |> List.map ((<|) g) |> List.sum





g : Int -> Int

g x =

    x * 2

Note that you had an error in the type signature for g

answered Nov 22 '18 at 11:55

Simon H

12.8k74477

answered Nov 22 '18 at 11:55

Simon H

12.8k74477

answered Nov 22 '18 at 11:55

Simon H

12.8k74477

answered Nov 22 '18 at 11:55

Simon H

12.8k74477

Corrected, good point - as every function is curried (as I understand). Thanks for the answer.

– Oskar Szura
Nov 25 '18 at 20:17

add a comment |

Corrected, good point - as every function is curried (as I understand). Thanks for the answer.

– Oskar Szura
Nov 25 '18 at 20:17

Corrected, good point - as every function is curried (as I understand). Thanks for the answer.

– Oskar Szura
Nov 25 '18 at 20:17

add a comment |

how to use << and >> operators to achieve that? Is it even possible to compose multivariadic functions?

Yes, easily:

h = flip flip g << ((<<) (<<)) << ((>>) g) << f << g

h is a <function> : number -> number -> number -> number, which is the same as h a b c = f (g a) (g b) (g c).

I think we don't need to dig deep in the correctness, since it's obvious that the version with arguments is much more readable.

answered Nov 22 '18 at 14:03

Igor Drozdov

12k52444

Note that flip was removed from elm/core in 0.19, so I'd be very hesitant to accept this as a proper solution! /s

– glennsl
Nov 22 '18 at 15:14

thanks for the note about flip. my point in the answer is that it's possible to compose the functions in order to achieve the desired result, but it makes no sense since the code becomes less readable than straight solution

– Igor Drozdov
Nov 22 '18 at 15:29

Yeah, I got that, and I'm actually pretty impressed you managed (and bothered) to figure it out. Hence the (easily missed) "/s" to indicate sarcasm on my end ;)

– glennsl
Nov 22 '18 at 15:42

So practically it's possible but there's no point of doing so... Thanks for the answer :).

– Oskar Szura
Nov 25 '18 at 20:16

add a comment |

how to use << and >> operators to achieve that? Is it even possible to compose multivariadic functions?

Yes, easily:

h = flip flip g << ((<<) (<<)) << ((>>) g) << f << g

h is a <function> : number -> number -> number -> number, which is the same as h a b c = f (g a) (g b) (g c).

I think we don't need to dig deep in the correctness, since it's obvious that the version with arguments is much more readable.

answered Nov 22 '18 at 14:03

Igor Drozdov

12k52444

Note that flip was removed from elm/core in 0.19, so I'd be very hesitant to accept this as a proper solution! /s

– glennsl
Nov 22 '18 at 15:14

thanks for the note about flip. my point in the answer is that it's possible to compose the functions in order to achieve the desired result, but it makes no sense since the code becomes less readable than straight solution

– Igor Drozdov
Nov 22 '18 at 15:29

Yeah, I got that, and I'm actually pretty impressed you managed (and bothered) to figure it out. Hence the (easily missed) "/s" to indicate sarcasm on my end ;)

– glennsl
Nov 22 '18 at 15:42

So practically it's possible but there's no point of doing so... Thanks for the answer :).

– Oskar Szura
Nov 25 '18 at 20:16

add a comment |

how to use << and >> operators to achieve that? Is it even possible to compose multivariadic functions?

Yes, easily:

h = flip flip g << ((<<) (<<)) << ((>>) g) << f << g

h is a <function> : number -> number -> number -> number, which is the same as h a b c = f (g a) (g b) (g c).

I think we don't need to dig deep in the correctness, since it's obvious that the version with arguments is much more readable.

answered Nov 22 '18 at 14:03

Igor Drozdov

12k52444

how to use << and >> operators to achieve that? Is it even possible to compose multivariadic functions?

Yes, easily:

h = flip flip g << ((<<) (<<)) << ((>>) g) << f << g

h is a <function> : number -> number -> number -> number, which is the same as h a b c = f (g a) (g b) (g c).

I think we don't need to dig deep in the correctness, since it's obvious that the version with arguments is much more readable.

answered Nov 22 '18 at 14:03

Igor Drozdov

12k52444

answered Nov 22 '18 at 14:03

Igor Drozdov

12k52444

answered Nov 22 '18 at 14:03

Igor Drozdov

12k52444

answered Nov 22 '18 at 14:03

Igor Drozdov

12k52444

Note that flip was removed from elm/core in 0.19, so I'd be very hesitant to accept this as a proper solution! /s

– glennsl
Nov 22 '18 at 15:14

thanks for the note about flip. my point in the answer is that it's possible to compose the functions in order to achieve the desired result, but it makes no sense since the code becomes less readable than straight solution

– Igor Drozdov
Nov 22 '18 at 15:29

Yeah, I got that, and I'm actually pretty impressed you managed (and bothered) to figure it out. Hence the (easily missed) "/s" to indicate sarcasm on my end ;)

– glennsl
Nov 22 '18 at 15:42

So practically it's possible but there's no point of doing so... Thanks for the answer :).

– Oskar Szura
Nov 25 '18 at 20:16

add a comment |

Note that flip was removed from elm/core in 0.19, so I'd be very hesitant to accept this as a proper solution! /s

– glennsl
Nov 22 '18 at 15:14

thanks for the note about flip. my point in the answer is that it's possible to compose the functions in order to achieve the desired result, but it makes no sense since the code becomes less readable than straight solution

– Igor Drozdov
Nov 22 '18 at 15:29

Yeah, I got that, and I'm actually pretty impressed you managed (and bothered) to figure it out. Hence the (easily missed) "/s" to indicate sarcasm on my end ;)

– glennsl
Nov 22 '18 at 15:42

So practically it's possible but there's no point of doing so... Thanks for the answer :).

– Oskar Szura
Nov 25 '18 at 20:16

Note that flip was removed from elm/core in 0.19, so I'd be very hesitant to accept this as a proper solution! /s

– glennsl
Nov 22 '18 at 15:14

thanks for the note about flip. my point in the answer is that it's possible to compose the functions in order to achieve the desired result, but it makes no sense since the code becomes less readable than straight solution

– Igor Drozdov
Nov 22 '18 at 15:29

Yeah, I got that, and I'm actually pretty impressed you managed (and bothered) to figure it out. Hence the (easily missed) "/s" to indicate sarcasm on my end ;)

– glennsl
Nov 22 '18 at 15:42

So practically it's possible but there's no point of doing so... Thanks for the answer :).

– Oskar Szura
Nov 25 '18 at 20:16

add a comment |

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