3.6.4 Serializable Closures

(require web-server/private/closure)

The defunctionalization process of the Web Language (see Stateless Servlets) requires an explicit representation of closures that is serializable. "private/closure.ss" is this representation. It provides:

(make-closure-definition-syntax   tag             fvars             proc)   →   syntax?

tag : syntax?

fvars : (listof identifier?)

proc : syntax?

Outputs a syntax object that defines a serializable structure, with tag as the tag, that represents a closure over fvars, that acts a procedure and when invoked calls proc, which is assumed to be syntax of lambda or case-lambda.

(closure->deserialize-name c) → symbol?

c : closure?

Extracts the unique tag of a closure c.

These are difficult to use directly, so "private/define-closure.ss" defines a helper form:

(require web-server/private/define-closure)

(define-closure tag formals (free-vars ...) body)

Defines a closure, constructed with make-tag that accepts closure that returns freevars ..., that when invoked with formals executes body.

Here is an example:

#lang scheme

(require scheme/serialize)

(define-closure foo (a b) (x y)

(+ (- a b)

(* x y)))

(define f12 (make-foo (lambda () (values 1 2))))

(serialize f12)

'((1) 1 (('page . foo:deserialize-info)) 0 () () (0 1 2))

(f12 6 7)

1

(f12 9 1)

10

(define f45 (make-foo (lambda () (values 4 5))))

(serialize f45)

'((1) 1 (('page . foo:deserialize-info)) 0 () () (0 4 5))

(f45 1 2)

19

(f45 8 8)

20