Update for recent nim versions and add simple example

examples/simple.nim

@@ -0,0 +1,52 @@
+# Copyright 2021 Mattia Giambirtone
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# A simple REPL to parse and evaluate mathematical expressions
+
+
+import nimkalc
+
+import strformat
+import strutils
+
+
+proc repl() =
+  ## A simple REPL to demonstrate NimKalc's functionality
+  var result: AstNode
+  while true:
+    try:
+      stdout.write("=> ")
+      result = eval(stdin.readLine())
+      case result.kind:
+        # The result is an AstNode object, specifically
+        # either a node of type NodeKind.Float or a NodeKind.Integer
+        of NodeKind.Float:
+          echo result.value
+        of NodeKind.Integer:
+          echo int(result.value)
+        else:
+          discard  # Unreachable
+    except IOError:
+      echo "\nGoodbye."
+      break
+    except ParseError:
+      echo &"A parsing error occurred: {getCurrentExceptionMsg()}"
+    except MathError:
+      echo &"An arithmetic error occurred: {getCurrentExceptionMsg()}"
+    except OverflowDefect:
+      echo &"Value overflow/underflow detected: {getCurrentExceptionMsg()}"
+
+
+when isMainModule:
+  repl()

src/nimkalc/parsing/parser.nim

@@ -23,9 +23,6 @@ import strformat
 import tables
 
 
-{.experimental: "implicitDeref".}
-
-
 type
   Parser* = ref object
     tokens: seq[Token]