PLT 方案菜鸟：布尔值和/或不是过程？
我正在尝试为数字电子课程制作一个真值表生成器，因为这就是我在业余时间享受乐趣的方式，并且不要评判我。
无论如何，我想我应该有一个哈希，其中相当于运算符的字符串作为键，以及与这些运算符相对应的方案过程作为值。
例如，
(define operator-table #hash(("+" . or)
("*" . and)))
所以我可以做类似的事情
(lambda (a b) ((hash-ref operator-table (string-ref input-str i)) a b))
现在我意识到上面的方法可能无法正常工作，但事实上我什至无法修改它，直到我得到正确的结果，因为显然 and 和 或在Scheme中是特殊的。在 REPL 中，如果我输入 not，它会回复 #。但是，如果我给它 and 或 or，它会显示 and: bad syntax in: and。是否有我可以使用的 and 程序版本？或者我必须用 lambda 制作一个吗？或者我完全错过了一些东西？
我不从一开始就使用 lambda 的唯一原因是我不想失去内置 和 的可变数量能力 [我可以做 (and #t #f) 以及（和#t #f #f #t #f #t）]。
I'm trying to make a truth-table generator for a digital electronics course because that's how I have fun in my spare time and don't judge me.
Anywho, I figured I'd have a hash with the string equivalent of operators as keys, and the Scheme procedures that correspond to those operators as values.
E.g.
(define operator-table #hash(("+" . or)
("*" . and)))
So I could do something like
(lambda (a b) ((hash-ref operator-table (string-ref input-str i)) a b))
Now I realize the above probably won't work right, but as it is I can't even tinker with it until I get it right, because apparently and and or are special in Scheme. At the REPL, if I type in not it replies #<procedure:not>. But if I give it and or or, it says and: bad syntax in: and. Is there a procedure version of and I can use? Or do I have to make one with lambda? Or am I missing something entirely?
The only reason I didn't just go with lambda from the get-go is that I don't want to lose the variable-arity abilities of the builtin and [I can do (and #t #f) as well as (and #t #f #f #t #f #t)].
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如果你想使用
and和or的函数形式（限制它们不会短路）并且不丢失变量的arity属性，那么你可以轻松地这样做：（values是 (PLT) 方案中惯用的恒等函数。）If you want to use a function form of
andandor(with the limitation that they will not short-circuit) and not lose the variable arity property, then you can easily do so:(
valuesis the idiomatic identity function in (PLT) Scheme.)是的，它们不能是过程，因为Scheme（像大多数语言一样）是一种“热切”语言——过程的每个参数在过程控制（接收参数值）之前都会被评估。
and和or需要“短路”——一旦知道最终结果就停止参数评估——所以它们不能是常规过程/函数任何急切的语言（“惰性”语言，例如 Haskell——其中每个参数仅在需要时才被评估——是一个非常不同的品种，并且不需要这个“常规函数” “与“特殊形式”的区别......但是，可惜，Scheme 并不是其中之一！）。Yep, they can't be procedures because Scheme (like most languages) is an "eager" language -- every argument to a procedure gets evaluated before the procedure takes control (receiving the argument values).
andandorneed to "short-circuit" -- stop argument evaluation as soon as the final result is known -- so they can't be regular procedures/functions in any eager language ("lazy" languages, such as Haskell -- where each argument is evaluated only if, when and as needed -- are a very different breed, and don't need this "regular function" versus "special form" distinction... but, alas, Scheme just isn't one of those!).