[plt-dev] feature request

Yes, but I think the library should be combined with struct, which is why I am asking. 


On Apr 14, 2010, at 6:23 PM, Robby Findler wrote:

> This is probably obvious but you could write a pretty simple function
> to build the prefab struct out of the sexp and even put it in a
> library to be used as a replacement for read.
> 
> Robby
> 
> On Wednesday, April 14, 2010, Eli Barzilay <eli at barzilay.org> wrote:
>> On Apr 14, Matthias Felleisen wrote:
>>> A lot of libraries read in file content as lists (or S-expressions)
>>> of list-based structures (see csv on planet for one example, which I
>>> am currently incorporating to a small degree into
>>> 2htdp/batch-io). If I had this structure -- including in teaching
>>> languages -- I could easily 'view' these S-expressions/lists as
>>> structs, making for much more readable code.
>> 
>> +1 for the use case (but I don't have an opinion on whether it
>> justifies implementing them or not).  And here is how you do it in CL:
>> 
>> Plain list -- with the default keyworded constructor
>> 
>>  CL-USER(1): (defstruct (foo (:type list)) x y)
>>  FOO
>>  CL-USER(2): (make-foo :y 2 :x 1)
>>  (1 2)
>>  CL-USER(3): (foo-x (list 1 2))
>>  1
>> 
>> 
>> Tagged list, with a positional constructor with arguments in reverse
>> 
>>  CL-USER(4): (defstruct (foo (:type list) :named (:constructor mkfoo (y x)))
>>                x y)
>>  FOO
>>  CL-USER(5): (mkfoo 2 1)
>>  (FOO 1 2)
>>  CL-USER(6): (foo-p '(1 2))     ; ("-p" is a bad spelling for "?")
>>  NIL
>>  CL-USER(7): (foo-p '(foo 1 2))
>>  T
>>  CL-USER(8): (foo-x (mkfoo 2 1))
>>  1
>> 
>> 
>> --
>>          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
>>                    http://barzilay.org/                   Maze is Life!
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