On 08/25/2012 01:08 PM, Neil Toronto wrote:
On 08/25/2012 10:53 AM, Ryan Culpepper wrote:
On 08/25/2012 12:19 PM, Neil Toronto wrote:
I've reordered these a bit:
number
string
bytes
character
regexp
In other words, "literal data". But did you check that the '#%datum'
macro associated with them has the standard meaning? If not, they could
expand into arbitrary expressions (possibly with side effects)!
A number can expand to an arbitrary expression? How?
And what do you mean by "the '#%datum' macro associated with them"?
Applied to them?
> (let-syntax ([#%datum (lambda (stx) #'(printf "hello\n"))]) 5)
hello
In Racket, literal data carry lexical information just like identifiers.
When a literal datum is used as an expression, the macro expander
synthesizes a '#%datum' identifier that determines what to do with the
literal. The Racket '#%datum' macro just expands into a 'quote'
expression if the datum is not a keyword.
The implicit '#%app' syntax works similarly, except it takes its lexical
context from the pair that represents the application.
Ryan
_________________________
Racket Developers list:
http://lists.racket-lang.org/dev
