CODEWITHSUNDEEP
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Kevin Choi
Kevin Choi

Reputation: 765

Defining Monad Function?

v=: ((1 2);(3 4);(0 5);<(2 1))
d =: (1,0.5,1,0.25);(0.5,1,0.75,0.25);(1,0.75,1,0);(0.75,0.25,0,1)
force=:(v ((0{>"0 v);])@{~ ] i.4) ,"1 0 <"0>(0{d)
force=:(v ((1{>"0 v);])@{~ ] i.4) ,"1 0 <"0>(1{d)
force=:(v ((2{>"0 v);])@{~ ] i.4) ,"1 0 <"0>(2{d)
force=:(v ((3{>"0 v);])@{~ ] i.4) ,"1 0 <"0>(3{d)
force=:(v ((4{>"0 v);])@{~ ] i.4) ,"1 0 <"0>(4{d)
force=:(v ((y{>"0 v);])@{~ ] i.4) ,"1 0 <"0>(y{d)

Given v and d, 1st column of force gives us (n+1)th vector from v.

2nd column of force gives us each vector from v.

3rd column of force gives us a constant between 2 vectors.

That is, (1 2);(1 2) will have 1 on 3rd column of force, but (1 2);(3 4) might not. I want to make a monad function which gives us

force=:(v ((1{>"0 v);])@{~ ] i.4) ,"1 0 <"0>(1{d)

if we type force_constant 1

or force=:(v ((2{>"0 v);])@{~ ] i.4) ,"1 0 <"0>(2{d)

if we type force_constant 2

Could someone help?

Upvotes: 2

Views: 83

Answers (1)

Dan Bron
Dan Bron

Reputation: 2324

You wrote most of it yourself already. Just take your final version of force, the one you wrote using y, and wrap it in an explicit definition:

    v =:  ((1 2);(3 4);(0 5);<(2 1))
    d =:  (1,0.5,1,0.25);(0.5,1,0.75,0.25);(1,0.75,1,0);(0.75,0.25,0,1)

   force_constant =: monad def '(v ((y{>"0 v);])@{~ ] i.4) ,"1 0 <"0>(y{d)'

   force_constant 1
+---+---+----+
|3 4|1 2|0.5 |
+---+---+----+
|3 4|3 4|1   |
+---+---+----+
|3 4|0 5|0.75|
+---+---+----+
|3 4|2 1|0.25|
+---+---+----+

   force_constant 2
+---+---+----+
|0 5|1 2|1   |
+---+---+----+
|0 5|3 4|0.75|
+---+---+----+
|0 5|0 5|1   |
+---+---+----+
|0 5|2 1|0   |
+---+---+----+

Now, this formulation depends on the nouns v and d being globally defined. You might consider changing that so force_constant or related verbs take these arrays as inputs. The simplest method would be change the monads to dyads, and let v and d come in as the left argument, x¹.

¹But we can keep it simple for now. If you want more feedback on your code, feel free to post it over on http://codereview.stackexchange.com/.

Upvotes: 4

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