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Source for ticket #99

cc

changetime

2010-11-18 14:14:34

component

WG1 - Core

description

Email from Thomas Bushnell:

Ah. The usage case is where I want to have a top-level macro which expands into a series of top-level forms. For example, suppose I want `define-many` which looks like this:

{{{
(define-many foo bar baz quux)
}}}

and expands into:

{{{
(define foo #f)
(define bar #f)
(define baz #f)
(define quux #f)
}}}

However, `syntax-rules` doesn't permit a series of forms, so the R5RS solution is to put a `begin` around it, and then specify that `begin` doesn't change the top-level-ness of the forms inside it.  So this works:

{{{
(define-syntax define-many
  (syntax-rules ()
    ((_ name names ...) (begin (define name #f) (define names #f) ...))))
}}}

So far so good. But suppose now that the forms inside all need to make use of some special bit of local syntax. That is, I want to define some syntax which will ''not'' be visible at top-level, but will be used by the forms that `define-many` expands into. The solution should be to replace `begin` with `let-syntax` above, but you can't do it according to R5RS. Most Scheme folks that I know regard this as a bug, because a top-level `let-syntax` really can't have any other use.

id

99

keywords

milestone

owner

alexshinn

priority

major

reporter

cowan

resolution

duplicate

severity

status

closed

summary

Allow top-level LET-SYNTAX

time

2010-11-17 06:09:06

type

defect

Changes

Change at time 2010-11-18 14:14:34

author

alexshinn

field

comment

newvalue

`let-syntax` is allowed at top-level, as is any Scheme expression.
Using `let-syntax` to expand into definitions is a grey area,
already brought up by #48.

oldvalue

1

raw-time

1290060874000000

ticket

99

time

2010-11-18 14:14:34

Change at time 2010-11-18 14:14:34

author

alexshinn

field

resolution

newvalue

duplicate

oldvalue

raw-time

1290060874000000

ticket

99

time

2010-11-18 14:14:34

Change at time 2010-11-18 14:14:34

author

alexshinn

field

status

newvalue

closed

oldvalue

new

raw-time

1290060874000000

ticket

99

time

2010-11-18 14:14:34