* bug#32847: Wrong macro expansion in eval
@ 2018-09-26 20:02 Stefan Israelsson Tampe
2018-09-27 2:16 ` Mark H Weaver
0 siblings, 1 reply; 3+ messages in thread
From: Stefan Israelsson Tampe @ 2018-09-26 20:02 UTC (permalink / raw)
To: 32847
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This for guile 2.4 and master,
> (eval `(let-syntax ((f (lambda (x) ,#'(+ (pk 'a 1) 2)))) f) (cu
rrent-module))
;;; (#<syntax a> 1)
But without eval:
> (let-syntax ((f (lambda (x) #'(+ (pk 'a 1) 2)))) f)
;;; (a 1)
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^ permalink raw reply [flat|nested] 3+ messages in thread
* bug#32847: Wrong macro expansion in eval
2018-09-26 20:02 bug#32847: Wrong macro expansion in eval Stefan Israelsson Tampe
@ 2018-09-27 2:16 ` Mark H Weaver
2018-09-27 8:33 ` Stefan Israelsson Tampe
0 siblings, 1 reply; 3+ messages in thread
From: Mark H Weaver @ 2018-09-27 2:16 UTC (permalink / raw)
To: Stefan Israelsson Tampe; +Cc: 32847
Hi Stefan,
Stefan Israelsson Tampe <stefan.itampe@gmail.com> writes:
> This for guile 2.4 and master,
>
>> (eval `(let-syntax ((f (lambda (x) ,#'(+ (pk 'a 1) 2)))) f) (current-module))
>
> ;;; (#<syntax a> 1)
>
> But without eval:
>> (let-syntax ((f (lambda (x) #'(+ (pk 'a 1) 2)))) f)
>
> ;;; (a 1)
I think the mistake is in your code above. In the first case, what you
want is this:
(eval `(let-syntax ((f (lambda (x) ,'#'(+ (pk 'a 1) 2)))) f)
(current-module))
Note the addition of a quote (') between the unquote (,) and syntax (#')
above.
The expression that follows unquote (,) should evaluate to an
s-expression. In this case, you want it to evaluate to the s-expression
#'(+ (pk 'a 1) 2), i.e. (syntax (+ (pk 'a 1) 2)), i.e. a list with two
elements, the first being the symbol 'syntax'. But that's not what
you're doing above. Instead, you are returning the syntax object
itself, which is being spliced directly into the code.
Does that make sense?
Mark
^ permalink raw reply [flat|nested] 3+ messages in thread
* bug#32847: Wrong macro expansion in eval
2018-09-27 2:16 ` Mark H Weaver
@ 2018-09-27 8:33 ` Stefan Israelsson Tampe
0 siblings, 0 replies; 3+ messages in thread
From: Stefan Israelsson Tampe @ 2018-09-27 8:33 UTC (permalink / raw)
To: Mark H Weaver; +Cc: 32847
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yes that makes sense. thanks!
On Thu, Sep 27, 2018 at 4:16 AM Mark H Weaver <mhw@netris.org> wrote:
> Hi Stefan,
>
> Stefan Israelsson Tampe <stefan.itampe@gmail.com> writes:
>
> > This for guile 2.4 and master,
> >
> >> (eval `(let-syntax ((f (lambda (x) ,#'(+ (pk 'a 1) 2)))) f)
> (current-module))
> >
> > ;;; (#<syntax a> 1)
> >
> > But without eval:
> >> (let-syntax ((f (lambda (x) #'(+ (pk 'a 1) 2)))) f)
> >
> > ;;; (a 1)
>
> I think the mistake is in your code above. In the first case, what you
> want is this:
>
> (eval `(let-syntax ((f (lambda (x) ,'#'(+ (pk 'a 1) 2)))) f)
> (current-module))
>
> Note the addition of a quote (') between the unquote (,) and syntax (#')
> above.
>
> The expression that follows unquote (,) should evaluate to an
> s-expression. In this case, you want it to evaluate to the s-expression
> #'(+ (pk 'a 1) 2), i.e. (syntax (+ (pk 'a 1) 2)), i.e. a list with two
> elements, the first being the symbol 'syntax'. But that's not what
> you're doing above. Instead, you are returning the syntax object
> itself, which is being spliced directly into the code.
>
> Does that make sense?
>
> Mark
>
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