> On Mar 10, 2018, at 6:46 PM, Alex Knauth <alexan...@knauth.org> wrote:
> The macro expander merges syntax properties between the input of a macro and
> the output of a macro using `cons`. That means that if there is an
> identity-macro call like this:
> (identity-macro x)
> where both `x` and `(identity-macro x)` have the property `'prop = 5`, the
> final result has the property `'prop = (cons 5 5)`.
> To avoid this merging, I would like to "delete" the `'prop` property on the
> `x`. According to the docs for syntax property, it returns #false if no value
> is associated with the key. So it seems like the way to "delete" it is to set
> it to #false.
> However, this method of "deleting" doesn't get rid of the merging. Instead I
> get `'prop = (cons #false 5)`.
> Is there a better way of deleting properties?
In the expander code I found this :
(define (syntax-property-remove s key)
(if (hash-ref (syntax-props s) key #f)
(struct-copy syntax s
[props (hash-remove (syntax-props s) key)])
Is there a reason why this is not provided as part of the syntax property
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