Substitute constant values for DSKIP when initializing symbol table

Previously the interpreter could not handle constructions of the form

   CONSTANT(N, 100)
   DSKIP(N)

No error would be printed but the symbol table would be initialized
incorrectly.

hera/symtab.py

@@ -13,20 +13,26 @@ def get_symtab(program):
     dc = HERA_DATA_START
     for op in program:
         odc = dc
-        if op.name == "LABEL" and len(op.args) == 1:
-            labels[op.args[0]] = pc
-        elif op.name == "DLABEL" and len(op.args) == 1:
-            labels[op.args[0]] = dc
-        elif op.name == "CONSTANT" and len(op.args) == 2:
-            labels[op.args[0]] = op.args[1]
+        if op.name == "LABEL":
+            if len(op.args) == 1:
+                labels[op.args[0]] = pc
+        elif op.name == "DLABEL":
+            if len(op.args) == 1:
+                labels[op.args[0]] = dc
+        elif op.name == "CONSTANT":
+            if len(op.args) == 2:
+                labels[op.args[0]] = op.args[1]
         elif op.name == "INTEGER":
             dc += 1
-        elif op.name == "DSKIP" and len(op.args) == 1 and isinstance(op.args[0], int):
-            dc += op.args[0]
-        elif (
-            op.name == "LP_STRING" and len(op.args) == 1 and isinstance(op.args[0], str)
-        ):
-            dc += len(op.args[0]) + 1
+        elif op.name == "DSKIP":
+            if len(op.args) == 1:
+                if isinstance(op.args[0], int):
+                    dc += op.args[0]
+                elif op.args[0] in labels:
+                    dc += labels[op.args[0]]
+        elif op.name == "LP_STRING":
+            if len(op.args) == 1 and isinstance(op.args[0], str):
+                dc += len(op.args[0]) + 1
         else:
             pc += len(convert(op))
 

test/test_integration.py

@@ -367,13 +367,13 @@ def test_cs240_array_dot_hera():
 
     assert not vm.flag_sign
     assert vm.flag_zero
-    assert not vm.flagoverflow
+    assert not vm.flag_overflow
     assert vm.flag_carry
     assert not vm.flag_carry_block
 
     for i in range(100):
-        assert vm.memory[HERA_DATA_START+i] == i+1
-    assert vm.memory[HERA_DATA_START+100] == 5050
+        assert vm.memory[HERA_DATA_START + i] == i + 1
+    assert vm.memory[HERA_DATA_START + 100] == 5050
 
 
 def test_error_message_for_missing_comma(capsys):