如何在 PicoLisp 中使用 `cond` return 默认值

Question

当 cond 语句不满足其他条件时，我正在尝试 return 默认值。我怎样才能在 PicoLisp 中实现这一点？

(de fib (n)
  (cond
    ((= n 0) 0)
    ((= n 1) 1)
    (+ (fib (- n 1)) (fib (- n 2))) ) )

(prinl (fib 1)) # prints 1
(prinl (fib 5)) # prints nothing
(bye)

Example coded with this reference code.

(let (Foo "bar")
  (cond
    ((not Foo) "No foo for you")
    ((lst? Foo) (map 'my-list-function Foo))
    ((= Foo "bar") "Foobar")
    "Nothing is true" ) )

Answer 1

您必须使用 T global to return a default value with cond。

(de fib (n)
  (cond
    ((= n 0) 0)
    ((= n 1) 1)
    (T (+ (fib (- n 1)) (fib (- n 2)))) ) )

(prinl (fib 1)) # prints 1
(prinl (fib 5)) # prints 5
(bye)