Costabs-CoFloCo-TermDepth/calculator_simple.abs:46:38:Name expr cannot be resolved.
def Nat start(Expr exp) = eval_simple(expr);
-------------------------------------^
Costabs-CoFloCo-TermDepth/calculator_simple.abs:46:26:Type <UNKNOWN> does not match declared type CalculatorSimple.Expr.
def Nat start(Expr exp) = eval_simple(expr);
-------------------------^

Compilation failed with syntax errors.