# Normalization by Evaluation

• Evaluation = Compute the value of closed expressions (no free variables)
• E.g. evaluation of arithmetic expressions in primary school: $$(11 + 9) \times (2 + 4) = 120$$
• Normalization = Bring expressions with unknowns into a canonical form
• E.g. simplification in secondary school: $$(a + b)(a - b) = a^2 - b^2$$
• Normalization of Evaluation (NBE) = Adaption of an interpreter to simplify expressions containing unknowns