🐐 Array slicing

centvrion/ast_nodes.py

@@ -847,6 +847,49 @@ class ArrayIndex(Node):
     return vtable, lst[i - 1]
 
 
+def _to_index_int(val):
+  if isinstance(val, ValInt):
+    return val.value()
+  if isinstance(val, ValFrac) and val.value().denominator == 1:
+    return val.value().numerator
+  raise CentvrionError("Array index must be a number")
+
+
+class ArraySlice(Node):
+  def __init__(self, array, from_index, to_index) -> None:
+    self.array = array
+    self.from_index = from_index
+    self.to_index = to_index
+
+  def __eq__(self, other):
+    return (type(self) == type(other)
+      and self.array == other.array
+      and self.from_index == other.from_index
+      and self.to_index == other.to_index)
+
+  def __repr__(self) -> str:
+    return f"ArraySlice({self.array!r}, {self.from_index!r}, {self.to_index!r})"
+
+  def print(self):
+    return f"{self.array.print()}[{self.from_index.print()} VSQVE {self.to_index.print()}]"
+
+  def _eval(self, vtable):
+    vtable, array = self.array.eval(vtable)
+    vtable, from_val = self.from_index.eval(vtable)
+    vtable, to_val = self.to_index.eval(vtable)
+    if not isinstance(array, ValList):
+      raise CentvrionError("Cannot slice a non-array value")
+    from_int = _to_index_int(from_val)
+    to_int = _to_index_int(to_val)
+    lst = array.value()
+    if from_int < 1 or to_int > len(lst) or from_int > to_int:
+      raise CentvrionError(
+        f"Slice [{from_int} VSQVE {to_int}] out of range"
+        f" for array of length {len(lst)}"
+      )
+    return vtable, ValList(lst[from_int - 1 : to_int])
+
+
 class SiStatement(Node):
   def __init__(self, test, statements, else_part) -> None:
     self.test = test