Change lookup of Symbol and Bytecode names to use constants

- they used metaprogramming before, but that does not seem to work.
- RPython gives me 'operation cannot succeed' and conflicting types for variables if I try to change the code slightly
-> will just use simple constants instead, less maintainable but it works
Signed-off-by: Stefan Marr <git@stefan-marr.de>

src/som/compiler/symbol.py

-from rpython.rlib.unroll import unrolling_iterable
-
 # Symbol is a 'lightweight' enum, in Python 3.4, we could use Enum as superclass
 class Symbol(object):
     NONE             = -1
@@ -34,17 +32,41 @@ class Symbol(object):
     Keyword          = 28
     KeywordSequence  = 29
     OperatorSequence = 30
+    
+    _names = ("Integer",
+              "Not",
+              "And",
+              "Or",
+              "Star",
+              "Div",
+              "Mod",
+              "Plus",
+              "Minus",
+              "Equal",
+              "More",
+              "Less",
+              "Comma",
+              "At",
+              "Per",
+              "NewBlock",
+              "EndBlock",
+              "Colon",
+              "Period",
+              "Exit",
+              "Assign",
+              "NewTerm",
+              "EndTerm",
+              "Pound",
+              "Primitive",
+              "Separator",
+              "STString",
+              "Identifier",
+              "Keyword",
+              "KeywordSequence",
+              "OperatorSequence")
 
 def symbol_as_str(symbol):
-    symbols = unrolling_iterable(int_constants_of(Symbol))
-    for (key, val) in symbols:
-        if val == symbol:
-            return key
-    raise ValueError('No Symbol defined for the value %d.' % symbol)
-
-def int_constants_of(cls):
-    out = {}
-    for key, value in cls.__dict__.items():
-        if isinstance(value, int):
-            out[key] = value
-    return out
+    if symbol == -1:
+        return "NONE"
+    else:
+        return Symbol._names[symbol]

src/som/interpreter/bytecodes.py

-from rpython.rlib.unroll import unrolling_iterable
-
 class Bytecodes(object):
     
     # Bytecodes used by the Simple Object Machine (SOM)
@@ -58,7 +56,23 @@ class Bytecodes(object):
                               0,                                # return_local    
                               0 )                               # return_non_local
 
-    
+    _bytecode_names = ("HALT",
+                       "DUP",
+                       "PUSH_LOCAL",
+                       "PUSH_ARGUMENT",
+                       "PUSH_FIELD",
+                       "PUSH_BLOCK",
+                       "PUSH_CONSTANT",
+                       "PUSH_GLOBAL",
+                       "POP",
+                       "POP_LOCAL",
+                       "POP_ARGUMENT",
+                       "POP_FIELD",
+                       "SEND",
+                       "SUPER_SEND",
+                       "RETURN_LOCAL",
+                       "RETURN_NON_LOCAL")
+
 def bytecode_length(bytecode):
     return Bytecodes._bytecode_length[bytecode]
 
@@ -77,17 +91,5 @@ def bytecode_stack_effect_depends_on_send(bytecode):
 def bytecode_as_str(bytecode):
     if not isinstance(bytecode, int):
         raise ValueError('bytecode is expected to be an integer.')
-    
-    bytecodes = unrolling_iterable(int_constants_of(Bytecodes))
-    for key, val in bytecodes:
-        if val == bytecode:
-            return key.upper()
-        
-    raise ValueError('No defined defined for the value %d.' % bytecode)
-
-def int_constants_of(cls):
-    out = {}
-    for key, value in cls.__dict__.items():
-        if isinstance(value, int):
-            out[key] = value
-    return out
+    assert bytecode >= 0 and bytecode <= Bytecodes._num_bytecodes
+    return Bytecodes._bytecode_names[bytecode]