d: examples: reduce scopes

* data/skeletons/lalr1.d (YYLocation.step): New.
* examples/d/calc/calc.y (Lexer): Reduce scopes to avoid uninitialized
varibles.
Factor the handling of locations.
We don't need lenChars.

data/skeletons/lalr1.d

@@ -164,7 +164,8 @@ public struct ]b4_location_type[
    * Create a <code>Location</code> denoting an empty range located at
    * a given point.
    * @@param loc The position at which the range is anchored.  */
-  public this (Position loc) {
+  public this(Position loc)
+  {
     this.begin = this.end = loc;
   }
 
@@ -172,16 +173,25 @@ public struct ]b4_location_type[
    * Create a <code>Location</code> from the endpoints of the range.
    * @@param begin The first position included in the range.
    * @@param end   The first position beyond the range.  */
-  public this (Position begin, Position end)
+  public this(Position begin, Position end)
   {
     this.begin = begin;
     this.end = end;
   }
 
+  /**
+   * Reset initial location to final location.
+   */
+  public void step()
+  {
+    this.begin = this.end;
+  }
+
   /**
    * A representation of the location.
    */
-  public string toString () const {
+  public string toString() const
+  {
     auto end_col = 0 < end.column ? end.column - 1 : 0;
     auto res = begin.toString ();
     if (end.filename && begin.filename != end.filename)

examples/d/calc/calc.y

@@ -115,10 +115,10 @@ if (isInputRange!R && is(ElementType!R : dchar))
     // Skip initial spaces
     while (!input.empty && input.front != '\n' && isWhite(input.front))
     {
-      location.begin = location.end;
       location.end.column++;
       input.popFront;
     }
+    location.step();
 
     if (input.empty)
       return Symbol(TokenKind.YYEOF, location);
@@ -126,8 +126,6 @@ if (isInputRange!R && is(ElementType!R : dchar))
     // Numbers.
     if (input.front.isNumber)
     {
-      int ival;
-      int lenChars = 0;
       import std.compiler : version_minor;
       static if (version_minor >= 95)
       {
@@ -136,29 +134,26 @@ if (isInputRange!R && is(ElementType!R : dchar))
         import std.typecons : Flag, Yes;
         import std.conv : parse;
         auto parsed = parse!(int, R, Yes.doCount)(input);
-        ival = parsed.data;
-        lenChars = cast(int) parsed.count;
+        int ival = parsed.data;
+        location.end.column += cast(int) parsed.count;
       }
       else
       {
         auto copy = input;
         import std.conv : parse;
-        ival = input.parse!int;
+        int ival = input.parse!int;
         while (!input.empty && copy.front != input.front)
         {
-          lenChars++;
+          location.end.column++;
           copy.popFront;
         }
       }
-      location.begin = location.end;
-      location.end.column += lenChars;
       return Symbol(TokenKind.NUM, ival, location);
     }
 
     // Individual characters
     auto ch = input.front;
     input.popFront;
-    location.begin = location.end;
     location.end.column++;
     switch (ch)
     {