Re: (declare (pure ...))
Hi Al, On a practical level, I would be sad if vector-ref, for example, was "impure", and thus compiling a vector-ref invalidated all previously- checked globals for the current scope. Likewise, I would prefer to declare a procedure using vector-ref as pure, to let csc know that it does not modify globals (or the filesystem etc). The function vector-ref doesn't stop being pure (i.e. referentially transparent) depending how you use it. The function is always referentially transparent -- the expression (vector-ref some-global-vec) isn't. Quoting from "Functional Programming in C++" by Ivan Čukić: > We’re going to define purity more precisely now, through a concept called referential transparency. Referential transparency is a characteristic of expressions, not just functions. Let’s say an expression is anything that specifies a computation and returns a result. We’ll say an expression is referentially transparent if the program wouldn’t behave any differently if we replaced the entire expression with just its return value. If an expression is referentially transparent, it has no observable side effects, and therefore all functions used in that expression are pure. (p.104) I think that part just decides whether the procedure is "pure", for whatever purity means. That doesn't say anything about what compiling a call to such a "pure" procedure means (can memoize the value or not, need to re-check globals or closures afterwards or not etc). Both the Declarations and Types manual pages say clearly it means "referencial transparency." And RE local state, that you asked in another email: my understanding is that that refers to variables belonging to the closure, that survive across calls. E.g.: (define foo (let ((x 0)) (lambda (y) (set! x (add1 x)) (* 2 y siiky
Re: (declare (pure ...))
Hi Al, what does (declare (pure ..)) mean to csc? Is the function supposed to be * only side-effect free, or ... * also return the same value when called with the same arguments? I can't remember where `(declare)` is documented, but I believe this [0] is also relevant. [0] https://wiki.call-cc.org/man/5/Types#purity Good luck! siiky
Re: compiler types: records / collections interaction
Hi Al, What combination of * define-record-type (srfi-9, srfi-99, chicken define-record, whatever) and * (declare type ...) can I use to inform the compiler that (for collections of myrec) vector- ref returns myrec's (likewise list car/cdr, hash-table-ref)? And that it needs not emit any instance-type-checking code for objects extracted from such collections? For "native" Scheme types, there's at least `list-of` and `vector-of` [0]. The type definitions of car/cdr, vector-ref, etc are in the file types.db (you can find it at $PREFIX/lib/chicken/11/types.db). For other data-structures you have to look at the specific implementation. For example, SRFI-69 [1] mentions types in the changelog. They're not mentioned in the docs, however, so you'll have to dig through the code to confirm this. Separately, how can I tell the compiler that fields in these records have certain types? Add type declarations for the implicitly-defined per-field accessors and mutators? To annotate the types of the fields of a record, take a look at defstruct[2]. There may be other alternatives, I only know of this one. [0] https://wiki.call-cc.org/man/5/Types#type-syntax [1] https://wiki.call-cc.org/eggref/5/srfi-69 [2] https://wiki.call-cc.org/eggref/5/typed-records#defstruct Good luck! siiky
Re: compile-time deserialization
Oh I forgot to mention you need an extra compiler flag to use it (-extend). And I also just remembered that I wrote a post about this at the time. (: https://siiky.srht.site/scheme/reader-syntax.html
Re: compile-time deserialization
Hi, You can use reader syntax[0]. Take a look at this SQL reader syntax[1,2] I wrote some time ago for inspiration (it should require very little changing). [0] https://api.call-cc.org/5/doc/chicken/read-syntax/set-read-syntax%21 [1] https://git.sr.ht/~siiky/save-for-later/tree/c7297083127ac1543bf6013e27259b35d07236ee/item/sql-reader-syntax/sql-reader-syntax.scm [2] https://git.sr.ht/~siiky/save-for-later/tree/c7297083127ac1543bf6013e27259b35d07236ee/item/sql-reader-syntax/example.scm siiky
