Feature: explicit string representation for enum fields

doc/manual.txt

@@ -634,6 +634,24 @@ enums as an index type for arrays. The procedures ``inc``, ``dec``, ``succ``
 and ``pred`` are not available for them either.
 
 
+The compiler supports the built-in stringify operator ``$`` for enumerations.
+The stringify's result can be controlled by specifying the string values to
+use explicitely:
+
+.. code-block:: nimrod
+
+  type
+    TMyEnum = enum
+      valueA = (0, "my value A"),
+      valueB = "value B",
+      valueC = 2,
+      valueD = (3, "abc")
+
+As can be seen from the example, it is possible to both specify a field's 
+ordinal value and its string value by using a tuple construction. It is also
+possible to only specify one of them.
+
+
 Subrange types
 ~~~~~~~~~~~~~~
 A `subrange`:idx: type is a range of values from an ordinal type (the base

rod/ccgtypes.nim

@@ -1,14 +1,14 @@
 #
 #
 #           The Nimrod Compiler
-#        (c) Copyright 2009 Andreas Rumpf
+#        (c) Copyright 2011 Andreas Rumpf
 #
 #    See the file "copying.txt", included in this
 #    distribution, for details about the copyright.
 #
 
 #var
-#  newDummyVar: int; // just to check the symbol file mechanism
+#  newDummyVar: int # just to check the symbol file mechanism
 
 # ------------------------- Name Mangling --------------------------------
 
@@ -688,7 +688,11 @@ proc genEnumInfo(m: BModule, typ: PType, name: PRope) =
     assert(typ.n.sons[i].kind == nkSym)
     field = typ.n.sons[i].sym
     elemNode = getNimNode(m)
-    app(enumNames, makeCString(field.name.s))
+    if field.ast == nil:
+      # no explicit string literal for the enum field, so use field.name:
+      app(enumNames, makeCString(field.name.s))
+    else:
+      app(enumNames, makeCString(field.ast.strVal))
     if i < length - 1: app(enumNames, ", " & tnl)
     if field.position != i: 
       appf(specialCases, "$1.offset = $2;$n", [elemNode, toRope(field.position)])

rod/semfold.nim

@@ -58,7 +58,11 @@ proc ordinalValToString(a: PNode): string =
     for i in countup(0, sonsLen(n) - 1): 
       if n.sons[i].kind != nkSym: InternalError(a.info, "ordinalValToString")
       var field = n.sons[i].sym
-      if field.position == x: return field.name.s
+      if field.position == x: 
+        if field.ast == nil: 
+          return field.name.s
+        else:
+          return field.ast.strVal
     InternalError(a.info, "no symbol for ordinal value: " & $x)
   else:
     result = $x

rod/semtypes.nim

@@ -1,7 +1,7 @@
 #
 #
 #           The Nimrod Compiler
-#        (c) Copyright 2010 Andreas Rumpf
+#        (c) Copyright 2011 Andreas Rumpf
 #
 #    See the file "copying.txt", included in this
 #    distribution, for details about the copyright.
@@ -25,7 +25,6 @@ proc semEnum(c: PContext, n: PNode, prev: PType): PType =
     counter, x: BiggestInt
     e: PSym
     base: PType
-    v: PNode
   counter = 0
   base = nil
   result = newOrPrevType(tyEnum, prev, c)
@@ -41,12 +40,25 @@ proc semEnum(c: PContext, n: PNode, prev: PType): PType =
     case n.sons[i].kind
     of nkEnumFieldDef: 
       e = newSymS(skEnumField, n.sons[i].sons[0], c)
-      v = semConstExpr(c, n.sons[i].sons[1])
+      var v = semConstExpr(c, n.sons[i].sons[1])
-      x = getOrdValue(v)
+      var strVal: PNode = nil
+      case skipTypes(v.typ, abstractInst).kind 
+      of tyTuple: 
+        if sonsLen(v) != 2: liMessage(v.info, errWrongNumberOfVariables)
+        strVal = v.sons[1] # second tuple part is the string value
+        if skipTypes(strVal.typ, abstractInst).kind notin {tyString, tyCstring}:
+          liMessage(strVal.info, errStringLiteralExpected)
+        x = getOrdValue(v.sons[0]) # first tuple part is the ordinal
+      of tyString, tyCstring:
+        strVal = v
+        x = counter
+      else:
+        x = getOrdValue(v)
       if i != 1: 
         if (x != counter): incl(result.flags, tfEnumHasWholes)
         if x < counter: 
           liMessage(n.sons[i].info, errInvalidOrderInEnumX, e.name.s)
+      e.ast = strVal # might be nil
       counter = x
     of nkSym: 
       e = n.sons[i].sym

tests/accept/run/spec.csv

@@ -20,6 +20,7 @@ tcontinuexc.nim;ECcaught
 tcopy.nim;TEMP=C:\Programs\xyz\bin
 tcurrncy.nim;25
 temit.nim;509
+tenumhole;my value A1my value Bconc2valueCabc4abc
 texcsub.nim;caught!
 texplicitgeneric1.nim;Key: 12 value: 12Key: 13 value: 13 Key: A value: 12 Key: B value: 13
 tfinally.nim;came here 3
@@ -44,6 +45,7 @@ tmultim1.nim;7
 tmultim2.nim;collide: unit, thing collide: unit, thing collide: thing, unit
 tmultim3.nim;Hi derived!
 tmultim4.nim;hello
+tnamedenumfields;my value A0my value Bconc1valueCabc3abc
 tnestif.nim;i == 2
 tnestprc.nim;10
 toop1.nim;34[]o 5

tests/accept/run/tenumhole.nim

@@ -0,0 +1,16 @@
+
+const
+  strValB = "my value B"
+
+type
+  TMyEnum = enum
+    valueA = (1, "my value A"),
+    valueB = strValB & "conc",
+    valueC,
+    valueD = (4, "abc")
+ 
+# trick the optimizer with a variable:
+var x = valueD
+echo valueA, ord(valueA), valueB, ord(valueB), valueC, valueD, ord(valueD), x
+
+

tests/accept/run/tnamedenumfields.nim

@@ -0,0 +1,17 @@
+
+const
+  strValB = "my value B"
+
+type
+  TMyEnum = enum
+    valueA = (0, "my value A"),
+    valueB = strValB & "conc",
+    valueC,
+    valueD = (3, "abc"),
+    valueE = 4
+
+# trick the optimizer with a variable:
+var x = valueD
+echo valueA, ord(valueA), valueB, ord(valueB), valueC, valueD, ord(valueD), x
+
+

todo.txt

@@ -1,5 +1,7 @@
 - we need a way to disable tests
 - deprecate ^ and make it available as operator
+- test branch coverage
+- checked exceptions
 
 
 High priority (version 0.9.0)

web/news.txt

@@ -23,6 +23,13 @@ Bugfixes
   anymore. 
 
 
+Changes affecting backwards compatibility
+-----------------------------------------
+
+- Operators starting with ``^`` are now right-associative and have the highest 
+  priority.
+
+
 Additions
 ---------
 
@@ -37,6 +44,10 @@ Additions
 - Added ``emit`` pragma for direct code generator control.
 - Additional operations were added to the ``complex`` module. 
 - Added ``strutils.formatFloat``,  ``strutils.formatBiggestFloat``.
+- A field in an ``enum`` may be given an explicit string representation. 
+  This yields more maintainable code than using a constant 
+  ``array[TMyEnum, string]`` mapping.
+
 
 
 2010-10-20 Version 0.8.10 released