Apply a function as a side effect to each sub-expression during evaluation
TraceScan[f, expr]
TraceScan[f, expr, form]
TraceScan[f, expr, s]
TraceScan[f, expr, form, fp]
TraceScan[Print, f[1, 2 + 3]]
→ f[1, 5]{c = 0;TraceScan[(c++)&, fib[10], fib[_Integer]], c}
→ {fib[10], 1}Block[{c = 0}, {TraceScan[c++&, FixedPoint[(# / 2 + 1 / #)&, 1.], (Plus | Times)[__ ? MachineNumberQ]], c}]
→ {1.414213562373095, 0}