In Common Lisp, evaluate the expression and predicate: What is the result of (minusp (- 20 4 8 8 1)) ?

Introduction / Context: Common Lisp provides arithmetic operators and numeric predicates that return truth values. The function minusp tests whether a number is strictly less than zero. This question combines arithmetic evaluation with a predicate: you must first compute the numeric result of a subtraction expression and then apply minusp to that result.

Given Data / Assumptions:

• Expression to evaluate is (- 20 4 8 8 1).
• Predicate to apply is (minusp <number>), which returns T if <number> < 0, else NIL.
• In Common Lisp, subtraction with multiple arguments computes left-associative subtraction: a - b - c - d ...

Concept / Approach: Compute the inner arithmetic first, then use the predicate. Remember that T is Lisp’s canonical true value and NIL is false. Some Lisps also print NIL for false, not “F”. Therefore, the final answer must respect Lisp’s true/false conventions.

Step-by-Step Solution:

Verification / Alternative check: You can verify in a REPL: evaluating the arithmetic yields -1, and (minusp -1) returns T. Testing a non-negative like 0 would return NIL because 0 is not negative in Lisp’s numeric predicates.

Why Other Options Are Wrong:

• F: not a standard Lisp boolean; false is NIL.
• NIL: would be correct only if the number were non-negative.
• -20: confuses result with the original operand; the arithmetic result is -1, not -20.
• None of the above: incorrect because T is correct.

Common Pitfalls: Mis-evaluating multi-argument subtraction; assuming 0 is negative; confusing NIL with F; forgetting Lisp’s truth values and evaluation order (inner form first).

Final Answer: T