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added thomas alg in nim #399

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Merged
merged 9 commits into from
Oct 5, 2018
Merged

added thomas alg in nim #399

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818fd32
added thomas alg in nim
c252 Sep 29, 2018
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Update thomas_algorithm.nim
c252 Oct 3, 2018
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Update thomas_algorithm.nim
c252 Oct 3, 2018
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Update thomas_algorithm.nim
c252 Oct 3, 2018
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Update thomas_algorithm.nim
c252 Oct 4, 2018
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c252 Oct 5, 2018
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c252 Oct 5, 2018
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Merge branch 'master' into thomas_algorithm_in_nim
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fixed
c252 Oct 5, 2018
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34 changes: 34 additions & 0 deletions contents/thomas_algorithm/code/nim/thomas_algorithm.nim
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Original file line number Diff line number Diff line change
@@ -0,0 +1,34 @@
proc thomas_algorithm(a,b,c,d: var array[3,float]) =
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It's a personal bias of mine, but I prefer functions that don't modify the input. Is there an easy way to return the modified d without changing the original?

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I can do that, it might look less neat though. Because I would have to create new variables in the thomas alg proc and assign them to the inputs.

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You only need to copy c and d though, it's only a couple more lines... There should be some kind of copy function that does it.

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On that very same line: array[3,float].
Having a 3 there is a big no no!

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is that because the size shouldn't be hard coded?


let n: int = len(d)

c[0] = c[0] / b[0]
d[0] = d[0] / b[0]

for i in 1..n-1:
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There is accidental indentation from here to the end of the procedure. Also n-1 -> n - 1.

let scale: float = (1 / (b[i] - c[i-1] * a[i]))

c[i] = c[i] * scale
d[i] = (d[i] - a[i] * d[i - 1]) * scale

for i in countdown(n-2,0):
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(n-2,0) -> (n - 2, 0)

d[i] -= c[i]*d[i+1]



var x: array[3,float] = [0.0,2.0,3.0]
var y: array[3,float] = [1.0,3.0,6.0]
var z: array[3,float] = [4.0,5.0,0.0]
var w: array[3,float] = [7.0,5.0,3.0]
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If you make your thomas_algorithm pure, then you can change the var to const.


echo "The system,"
echo "[1.0 4.0 0.0][x] = [7.0]"
echo "[2.0 3.0 5.0][x] = [5.0]"
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I would write [y] and [z] instead fo [x] everywhere

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yeah that was a copy paste fail on my part.

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Don't forget to fix this :)

echo "[0.0 3.0 6.0][x] = [3.0]"

echo "has the solution:"

thomas_algorithm(x,y,z,w)

for i in 0..2:
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Can you calculate this range based on the number of equations again, rather than have it be hard-coded?

echo w[i]
4 changes: 3 additions & 1 deletion contents/thomas_algorithm/thomas_algorithm.md
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Expand Up @@ -113,8 +113,10 @@ You will find this algorithm implemented [in this project](https://scratch.mit.e
[import, lang:"haskell"](code/haskell/thomas.hs)
{% sample lang="swift" %}
[import, lang:"swift"](code/swift/thomas.swift)
{%sample lang="nim" %}
[import, lang:"nim"](code/nim/thomas_algorithm.nim)
{% endmethod %}

<script>
MathJax.Hub.Queue(["Typeset",MathJax.Hub]);
</script>
</script>