1 files changed, 85 insertions, 0 deletions
diff --git a/tests/converter/tgenericconverter2.nim b/tests/converter/tgenericconverter2.nim
new file mode 100644
index 000000000..97b7846c1
--- /dev/null
+++ b/tests/converter/tgenericconverter2.nim
@@ -0,0 +1,85 @@
+# bug #3799
+
+import strutils
+
+const output = splitLines("""
+00000000000000000000000000000000000000000
+00000000000001111111111111110000000000000
+00000000001111111111111111111110000000000
+00000000111111111111111111111111100000000
+00000011111222222221111111111111111000000
+00000111122222222222221111111111111100000
+00001112222333333459432111111111111110000
+00011122355544344463533221111111111111000
+00111124676667556896443322211111111111100
+00111126545561919686543322221111111111100
+01111123333346967807554322222211111111110
+01111122233334455582015332222221111111110
+01111122222333344567275432222222111111110
+01111112222222334456075443222222211111110
+01111111222222233459965444332222221111110
+01111111122222223457486554433322222111110
+01111111112222222367899655543333322111110
+01111111111122222344573948465444332111110
+00111111111112222334467987727667762111100
+00111111111111122233474655557836432111100
+00011111111111112233 454433334 4321111000
+00001111111111111122354333322222211110000
+00000111111111111111222222222222111100000
+00000001111111111111111122222111110000000
+00000000111111111111111111111111100000000
+00000000000111111111111111111100000000000
+00000000000000111111111111100000000000000
+""")
+
+const nmax = 500
+
+type
+  Complex*[T] = object
+    re*: T
+    im*: T
+
+converter toComplex*[T](x: tuple[re, im: T]): Complex[T] =
+  result.re = x.re
+  result.im = x.im
+
+
+proc julia*[T](z0, c: Complex[T], er2: T, nmax: int): int =
+  result = 0
+  var z = z0
+  var sre = z0.re * z0.re
+  var sim = z0.im * z0.im
+  while (result < nmax) and (sre + sim < er2):
+    z.im = z.re * z.im
+    z.im = z.im + z.im
+    z.im = z.im + c.im
+    z.re = sre - sim + c.re
+    sre = z.re * z.re
+    sim = z.im * z.im
+    inc result
+
+template dendriteFractal*[T](z0: Complex[T], er2: T, nmax: int): int =
+  julia(z0, (T(0.0), T(1.0)), er2, nmax)
+
+iterator stepIt[T](start, step: T, iterations: int): (int, T) =
+  for i in 0 .. iterations:
+    yield (i, start + T(i) * step)
+
+var errors = 0
+
+let c = (0.36237, 0.32)
+for j, y in stepIt(2.0, -0.0375 * 4, 107 div 4):
+  var row = ""
+  for i, x in stepIt(-2.0, 0.025 * 4, 160 div 4):
+    #let n = julia((x, y), c, 4.0, nmax)         ### this works
+    let n = dendriteFractal((x, y), 4.0, nmax)
+    let c = char(int('0') + n mod 10)
+    let e = output[j][i]  # expected
+    if c != e:
+      errors += 1
+    row.add(c)
+
+  # Printing apparently makes the test fail when joined.
+  # echo row
+
+doAssert errors < 10, "total errors: " & $errors