编写Scheme数据结构，以便可以对它们进行eval-d返回，或者替代
我正在 PLT 方案中编写一个应用程序（杂耍图案动画师）接受Scheme表达式作为某些字段的值。我正在尝试编写一个小型文本编辑器，它让我将表达式“分解”为仍然可以评估但包含文本数据的表达式以进行手动调整。
例如，
(4hss->sexp "747")
是生成合法模式的函数调用。如果我评估并打印它，它就
(((7 3) - - -) (- - (4 2) -) (- (7 2) - -) (- - - (7 1)) ((4 0) - - -) (- - (7 0) -) (- (7 2) - -) (- - - (4 3)) ((7 3) - - -) (- - (7 0) -) (- (4 1) - -) (- - - (7 1)))
可以作为字符串“读取”，但不会像函数一样“评估”。当然，对于这个陈述，我需要的很简单，
(quote (((7 3...
但其他例子并不简单。例如，这个包含打印为向量的结构：
pair-of-jugglers
; -->
(#(struct:hand #(struct:position -0.35 2.0 1.0) #(struct:position -0.6 2.05 1.1) 1.832595714594046) #(struct:hand #(struct:position 0.35 2.0 1.0) #(struct:position 0.6 2.0500000000000003 1.1) 1.308996938995747) #(struct:hand #(struct:position 0.35 -2.0 1.0) #(struct:position 0.6 -2.05 1.1) -1.3089969389957472) #(struct:hand #(struct:position -0.35 -2.0 1.0) #(struct:position -0.6 -2.05 1.1) -1.8325957145940461))
我想到了至少三种可能的解决方案，但我不太喜欢其中任何一个。
在我再次开始做糟糕的递归梦之前帮助我吧。
I'm writing an application (A juggling pattern animator) in PLT Scheme that accepts Scheme expressions as values for some fields. I'm attempting to write a small text editor that will let me "explode" expressions into expressions that can still be eval'd but contain the data as literals for manual tweaking.
For example,
(4hss->sexp "747")
is a function call that generates a legitimate pattern. If I eval and print that, it becomes
(((7 3) - - -) (- - (4 2) -) (- (7 2) - -) (- - - (7 1)) ((4 0) - - -) (- - (7 0) -) (- (7 2) - -) (- - - (4 3)) ((7 3) - - -) (- - (7 0) -) (- (4 1) - -) (- - - (7 1)))
which can be "read" as a string, but will not "eval" the same as the function. For this statement, of course, what I need would be as simple as
(quote (((7 3...
but other examples are non-trivial. This one, for example, contains structs which print as vectors:
pair-of-jugglers
; -->
(#(struct:hand #(struct:position -0.35 2.0 1.0) #(struct:position -0.6 2.05 1.1) 1.832595714594046) #(struct:hand #(struct:position 0.35 2.0 1.0) #(struct:position 0.6 2.0500000000000003 1.1) 1.308996938995747) #(struct:hand #(struct:position 0.35 -2.0 1.0) #(struct:position 0.6 -2.05 1.1) -1.3089969389957472) #(struct:hand #(struct:position -0.35 -2.0 1.0) #(struct:position -0.6 -2.05 1.1) -1.8325957145940461))
I've thought of at least three possible solutions, none of which I like very much.
Help me out before I start having bad recursion dreams again.
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我不确定你想做什么。具体来说，尝试生成具有可 eval 的代码的文件似乎是一个奇怪的选择。无论如何，当您处理结构时，创建随机值的序列化都是一个问题——因为可能存在具有相同名称的不同结构。一些可能与您相关的要点：
有一个未记录的库
scheme/fasl，它可以以二进制格式读取和写入值（对于大数据有用）。还有
mzlib/pconvert—— DrScheme 用来将值打印为可计算表达式的库（但这不适用于所有类型的数据）。如果你想使用很容易以可读形式编写的结构，那么你可以使用“预制”结构。
（有关更多详细信息，最好在邮件列表上询问。）
I'm not sure what you're trying to do. Specifically, trying to produce a file with
eval-able code seems like a strange choice. In any case, creating a serialization of random values is a problem when you're dealing with structs -- since there could be different structs with the same name. Some points that might be relevant for you:There is an undocumented library
scheme/faslthat can read and write values in binary format (useful for large data).There is also
mzlib/pconvert-- a library that DrScheme uses to print values as expressions that can be evaluated (but this won't work on all kinds of data).If you want to use structs that are very easy to write in a readable form, then you can use "prefab" structs.
(For more details it's probably best to ask on the mailing list.)