[racket-users] Re: Pretty Printing for ASTs represented as structs

[Jeremy Siek]

Thanks for the tip!

I found the following to work pretty well :)

#lang racket
(require racket/match)
(require racket/struct)

(struct Var (name)
   #:methods gen:custom-write
  [(define (write-proc ast port mode)
 (match ast
   [(Var x)
(write x port)]))])

(struct Num (value) 
   #:methods gen:custom-write
  [(define (write-proc ast port mode)
 (match ast
   [(Num n)
(write n port)]))])

(struct Let (var rhs body)
  #:methods gen:custom-write
  [(define write-proc
 (make-constructor-style-printer
  (lambda (obj) 'let)
  (lambda (obj) (list (unquoted-printing-string "([")
  (Let-var obj)
  (Let-rhs obj)
  (unquoted-printing-string "])\n")
  (Let-body obj)])
  
(define x (Var 'x))
(define y (Var 'y))
(define n (Num 42))
(define l (Let x n (Let y n x)))
(pretty-print l)

Produced the output:

(let ([ x 42 ])
 (let ([ y 42 ])
 x))


On Sunday, August 16, 2020 at 5:10:20 PM UTC-4 jackh...@gmail.com wrote:

> I recommend using make-constructor-style-printer 
> ,
>  
> which automates a lot of the fiddly indentation-handling you'd have to do 
> otherwise.
> On Sunday, August 16, 2020 at 1:48:50 PM UTC-7 jerem...@gmail.com wrote:
>
>>
>> Hi All,
>>
>> I'm looking into using Racket structs to represent abstract syntax trees.
>> I've gotten as far as defining gen:custom-write properties, but have not
>> yet figured out how to control indenting. Also, I'm not sure I'm just 
>> calling
>> write-string, write, and newline in my gen:custom-write methods, which I
>> suspect is not exactly correct.
>>
>> Are there some good up-to-date examples of this that I could look at?
>>
>> Thanks,
>> Jeremy
>>
>

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[racket-users] Re: Pretty Printing for ASTs represented as structs

[jackh...@gmail.com]

I recommend using make-constructor-style-printer 
,
 
which automates a lot of the fiddly indentation-handling you'd have to do 
otherwise.
On Sunday, August 16, 2020 at 1:48:50 PM UTC-7 jerem...@gmail.com wrote:

>
> Hi All,
>
> I'm looking into using Racket structs to represent abstract syntax trees.
> I've gotten as far as defining gen:custom-write properties, but have not
> yet figured out how to control indenting. Also, I'm not sure I'm just 
> calling
> write-string, write, and newline in my gen:custom-write methods, which I
> suspect is not exactly correct.
>
> Are there some good up-to-date examples of this that I could look at?
>
> Thanks,
> Jeremy
>

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