stack - 如何进行 OpenSCAD 类堆栈操作？

Question

我对 OpenSCAD 还很陌生，但大部分内容都已完成。但是，我不确定如何进行类似堆栈的操作。只要我可以推送和弹出数字，使用什么数据结构并不重要。这可能吗？

Answer 1

I worked extensively with stacks while implementing a string processing library.

The trick is to use nested right associative lists of size = 2, e.g. ["foo", ["bar", []]].

If you want to push something to a stack:

function push(stack, item) = [item, stack];

If you want to pop the stack:

function pop(stack) = stack[1];

And if you want to peek or retrieve the value that was popped:

function peek(stack) = stack[0];

You can also implement map/reduce functions using recursion:

function map(stack) = 
    push(
         map(pop(stack)),  
         f(peek(stack)) 
    );

function reduce(stack) = 
    f(peek(stack))? 
        push(
             reduce(pop(stack)),
             f(peek(stack))
        ) 
    : 
        reduce(pop(stack))
    ;

Of course, now that version 2015.03 is out you might consider using list comprehension, assuming that's what you really need.