defstruct could use compiler-syntax to speed up instance creation

[felix winkelmann]

By defining a compiler-macro on the constructor, keyword arguments can be pre-parsed and the constructor call be replaced by a direct structure value construction. Since this is applicable to various procedures, a general library procedure might be handy:

(unit eval)

(parse-keyword-arguments ARGLIST KEYS+DEFAULTS K) -> FORM

where K is a procedure TMPVARS -> BODY that returns a body. FORM is then a let* form binding temporaries to keep the original evaluation order of the arguments. In case of an invalid keyword argument list (computed keyword, missing keyword argument, non-keyword in keyword position, etc.) parse-keyword-arguments returns #f.

[felix winkelmann]

Added ##sys#parse-keyword-argument-list in 8f79e95e7a50a216f1c46e472263d566ef06de66 (experimental).

[felix winkelmann]

Replying to felix:

Added ##sys#parse-keyword-argument-list in 8f79e95e7a50a216f1c46e472263d566ef06de66 (experimental).

... and removed it again. It is better placed inside the defstruct code or into a separate extension.

[felix winkelmann]

No easy implementation: defstruct has to expand into a compiler-syntax definition that must pass a list of keywords and default arguments, but those arguments are quoted in the definition and will lose renaming information.

Currently not worth the trouble.