added a nim implementation of the forward euler method (#543)

Author: c252

contents/forward_euler_method/code/nim/forwardeuler.nim

@@ -0,0 +1,32 @@
+import math
+
+proc solveEuler(timestep: float, n: int): seq[float] =
+  var res = newSeq[float](n)
+  
+  res[0] = 1.0
+
+  for i in 1 .. n - 1:
+    res[i] = res[i - 1] - 3 * res[i - 1] * timestep
+
+  return res
+
+proc check(res: seq[float], timestep, threshold: float): bool =
+  var approx: bool = true;
+
+  for i in 0 .. len(res) - 1:
+    let solution: float = exp(-3.0 * float(i) * timestep)
+    if abs(res[i]) - solution > threshold:
+      echo res[i]
+      echo solution
+      approx = false
+
+  return approx
+
+const
+  timestep: float = 0.1
+  n: int = 100
+  threshold: float = 0.1
+  eulerResult: seq[float] = solveEuler(timestep, n)
+  approx: bool = check(eulerResult, threshold, timestep)
+
+echo approx

contents/forward_euler_method/forward_euler_method.md

@@ -132,6 +132,8 @@ Full code for the visualization follows:
 [import, lang:"asm-x64"](code/asm-x64/euler.s)
 {% sample lang="java" %}
 [import, lang:"java"](code/java/ForwardEuler.java)
+{% sample lang="nim" %}
+[import, lang:"nim"](code/nim/forwardeuler.nim)
 {% endmethod %}
 
 <script>