Add tasks for all the new languages

Task/Extend-your-language/Nim/extend-your-language.nim

@@ -0,0 +1,62 @@
+import macros
+
+proc newIfElse(c, t, e): PNimNode {.compiletime.} =
+  result = newIfStmt((c, t))
+  result.add(newNimNode(nnkElse).add(e))
+
+macro if2(x, y: expr; z: stmt): stmt {.immediate.} =
+  var parts: array[4, PNimNode]
+  for i in parts.low .. parts.high:
+    parts[i] = newNimNode(nnkDiscardStmt).add(nil)
+
+  assert z.kind == nnkStmtList
+  assert z.len <= 4
+
+  for i in 0 .. <z.len:
+    assert z[i].kind == nnkCall
+    assert z[i].len == 2
+
+    var j = 0
+
+    case $z[i][0].ident
+    of "then":  j = 0
+    of "else1": j = 1
+    of "else2": j = 2
+    of "else3": j = 3
+    else: assert false
+
+    parts[j] = z[i][1].last
+
+  result = newIfElse(x,
+    newIfElse(y, parts[0], parts[1]),
+    newIfElse(y, parts[2], parts[3]))
+
+if2 2 > 1, 3 < 2:
+  then:
+    echo "1"
+  else1:
+    echo "2"
+  else2:
+    echo "3"
+  else3:
+    echo "4"
+
+# Missing cases are supported:
+if2 2 > 1, 3 < 2:
+  then:
+    echo "1"
+  else2:
+    echo "3"
+  else3:
+    echo "4"
+
+# Order can be swapped:
+if2 2 > 1, 3 < 2:
+  then:
+    echo "1"
+  else2:
+    echo "3"
+  else1:
+    echo "2"
+  else3:
+    echo "4"