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Source for ticket #535

cc


    
changetime

    
2013-07-07 03:20:44

    
component

    
WG1 - Core

    
description

    
Michael Montague writes:

  I believe that a library should have at most one `begin` and it should have the semantics of a body (though no expressions are required). This would make the semantics of library bodies clear and make R7RS libraries much closer to R6RS libraries, with little loss in expressiveness.

The question is, what gain is to counterbalance that loss?  It's easy for users who agree with this to make sure their libraries have at most one `begin`, and likewise to reformat existing libraries if they feel strongly about it.  The benefit, then, must be to implementers -- but what benefit is that?  The `define-library` form must be read as a whole, and the first step will normally be to concatenate the `begin` declarations.

In addition, the restriction in the draft that imported identifiers cannot appear in a library textually before the `import` declaration that introduces them (see #353) means that it's possible to construct a library incrementally, adding new `import` and `begin` declarations as you go.  This is a convenience for programs that create libraries.

Without a definite improvement visible from the restriction to a single `begin` declaration, this proposal would indeed be one of those "weaknesses and restrictions" that the Scheme standards denounce.

    
id

    
535

    
keywords

    

    
milestone

    

    
owner

    
alexshinn

    
priority

    
major

    
reporter

    
cowan

    
resolution

    
wontfix

    
severity

    

    
status

    
closed

    
summary

    
Libraries should have at most one begin

    
time

    
2013-05-20 00:00:29

    
type

    
defect

    
Changes

    
Change at time 2013-07-07 03:20:44

    
author

    
cowan

    
field

    
comment

    
newvalue

    
The WG decided by unanimous consent to take no action on this ticket.

    
oldvalue

    
1

    
raw-time

    
1373142044410382

    
ticket

    
535

    
time

    
2013-07-07 03:20:44

    
Change at time 2013-07-07 03:20:44

    
author

    
cowan

    
field

    
resolution

    
newvalue

    
wontfix

    
oldvalue

    

    
raw-time

    
1373142044410382

    
ticket

    
535

    
time

    
2013-07-07 03:20:44

    
Change at time 2013-07-07 03:20:44

    
author

    
cowan

    
field

    
status

    
newvalue

    
closed

    
oldvalue

    
new

    
raw-time

    
1373142044410382

    
ticket

    
535

    
time

    
2013-07-07 03:20:44