🐐 Array indexing

tests.py

@@ -5,7 +5,7 @@ from unittest.mock import patch
 from parameterized import parameterized
 
 from centvrion.ast_nodes import (
-  Bool, BinOp, BuiltIn, DataArray, DataRangeArray, Defini,
+  ArrayIndex, Bool, BinOp, BuiltIn, DataArray, DataRangeArray, Defini,
   Designa, DumStatement, Erumpe, ExpressionStatement, ID,
   Invoca, ModuleCall, Nullus, Numeral, PerStatement,
   Program, Redi, SiStatement, String, UnaryMinus,
@@ -231,6 +231,8 @@ error_tests = [
   ("DEFINI f (x, y) VT { REDI(x) }\nINVOCA f (I)", TypeError),   # too few args
   ("DEFINI f () VT { REDI(I) }\nINVOCA f (I)", TypeError),        # args to zero-param function
   ("SI NVLLVS TVNC { DESIGNA r VT I }", TypeError),               # NVLLVS cannot be used as boolean
+  ("[(I, II)][III]", IndexError),                                  # index too high
+  ("[(I, II)][-I]", IndexError),                                   # negative index
 ]
 
 class TestErrors(unittest.TestCase):
@@ -604,17 +606,17 @@ class TestEtAvt(unittest.TestCase):
 
 
 # --- Array indexing ---
-# Indexing is 0-based; NVLLVS serves as index 0
+# Indexing is 1-based; I is the first element
 
 array_index_tests = [
   # basic indexing
-  ("[(I, II, III)][NVLLVS]", None, ValInt(1)),   # index 0 → first element
-  ("[(I, II, III)][I]", None, ValInt(2)),          # index 1 → second element
-  ("[(I, II, III)][II]", None, ValInt(3)),          # index 2 → third element
+  ("[(I, II, III)][I]", None, ValInt(1)),    # first element
+  ("[(I, II, III)][II]", None, ValInt(2)),   # second element
+  ("[(I, II, III)][III]", None, ValInt(3)),  # third element
   # index into a variable
-  ("DESIGNA a VT [(X, XX, XXX)]\na[I]", None, ValInt(20)),
+  ("DESIGNA a VT [(X, XX, XXX)]\na[II]", None, ValInt(20)),  # second element
   # index into range array
-  ("[I VSQVE V][II]", None, ValInt(3)),
+  ("[I VSQVE V][II]", None, ValInt(2)),      # second element of [1,2,3,4]
 ]
 
 class TestArrayIndex(unittest.TestCase):