6.8.11 Integrable expressions and functions

Compilers act upon “compilation units”, which for Vicare are: R6RS libraries, R6RS programs, symbolic expressions handed to eval; the latter includes standalone expressions typed at the REPL. Under Vicare:

• Whenever a function defined in a compilation unit is called in the same compilation unit: the compiler has access to the source code, so it always attempts to integrate it (expand it inline); such integration can succeed or fail depending on the cost of such operation.
• Whenever a function defined in a compilation unit is called in another compilation unit: the compiler has no access to the source code, so it never attempts to integrate it.

this scenario is somewhat different from the one of languages like C, which make use of object files that allow inlining of functions defined in other files.

Sometimes we do want to always integrate expressions, even across compilation unit boundaries; for this purpose Vicare provides define-inline to integrate expressions and define-integrable to integrate functions.

Syntax: define-inline (?name ?arg ... . ?rest) ?body0 ?body ...

Similar to define, but create a binding for an expression that is always expanded inline and can neither be invoked recursively nor used as function argument. This syntax only defines a syntax embedding the source code of the expression in a syntax object.

(define-inline (incr x)
  (+ x 1))

(incr 2)        ⇒ 3

In the example above, we can think of (incr 2) as expanding to:

(let ((x 2))
  (+ x 1))

Syntax: define-integrable (?name ?arg ... . ?rest) ?body0 ?body ...

Similar to define, but create a binding that is always expanded inline and can be both invoked recursively and used as function argument. This syntax defines both a syntax and a function, with the syntax embedding the source code of the function in a syntax object.

(define-integrable (incr x)
  (+ x 1))

(incr 2)
⇒ 3

(map incr '(10 20 30)))
⇒ (11 21 31)

In the example above, we can think of (incr 2) as expanding to:

((lambda (x)
   (+ x 1))
 2)