for S being Language
for U being non empty set
for phi being 0wff string of S
for I being b₁,b₂ -interpreter-like Function holds
( ( (S -firstChar) . phi <> TheEqSymbOf S implies I -AtomicEval phi = (I . ((S -firstChar) . phi)) . ((I -TermEval) * (SubTerms phi)) ) & ( (S -firstChar) . phi = TheEqSymbOf S implies I -AtomicEval phi = (U -deltaInterpreter) . ((I -TermEval) * (SubTerms phi)) ) )