added thomas alg in nim (#399)

implemented thomas algorithm in nim

Author: c252

contents/thomas_algorithm/code/nim/thomas_algorithm.nim

@@ -0,0 +1,39 @@
+proc thomas_algorithm(a, b, c_in, d_in: seq[float]): seq[float] = 
+
+  let n: int = len(d_in)
+
+  var c: seq[float] = c_in
+  var d: seq[float] = d_in
+    
+  c[0] /= b[0]
+  d[0] /= b[0]
+
+  for i in 1..n - 1:
+    let scale: float = (1 / (b[i] - c[i - 1] * a[i]))
+
+    c[i] *= scale
+    d[i] = (d[i] - a[i] * d[i - 1]) * scale
+
+  for i in countdown(n - 2,0):
+    d[i] -= c[i] * d[i + 1]
+
+  
+  return d
+            
+
+const x: seq[float] = @[0.0, 2.0, 3.0]
+const y: seq[float] = @[1.0, 3.0, 6.0]
+const z: seq[float] = @[4.0, 5.0, 0.0]
+const w: seq[float] = @[7.0, 5.0, 3.0]            
+            
+echo "The system,"
+echo "[1.0 4.0 0.0][x] = [7.0]"
+echo "[2.0 3.0 5.0][y] = [5.0]"
+echo "[0.0 3.0 6.0][z] = [3.0]"
+
+echo "has the solution:"
+
+const soln: seq[float] = thomas_algorithm(x, y, z, w)
+
+for i in 0..len(w) - 1:
+  echo soln[i]

contents/thomas_algorithm/thomas_algorithm.md

@@ -113,6 +113,8 @@ 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)
 {% sample lang="cpp" %}
 [import, lang:"c_cpp"](code/c++/thomas.cpp)
 {% endmethod %}