Final answer:
The evaluation of a let-expression in programming involves environment extension, evaluation of the first expression, substitution of the variable in the second expression, and the final evaluation of the modified second expression.
Step-by-step explanation:
The question refers to the evaluation process of a let-expression in the context of dynamic semantics in programming languages. A let-expression has the form let x = e1 in e2, where e1 is evaluated and bound to the variable x, which is then accessible in the expression e2. The evaluation of this expression involves four parts:
- Environment Extension: A new environment is created where the variable x is bound to the value resulting from evaluating expression e1.
- Evaluation of e1: The expression e1 is evaluated in the current environment to obtain its value.
- Substitution: In expression e2, every occurrence of variable x is replaced with the value obtained from evaluating e1.
- Final Evaluation: The modified expression e2, now with the value of e1 substituted for x, is evaluated to yield the final result of the let-expression.
Understanding these steps is crucial for comprehending how let-expressions function in programming languages that support them.