Formal comment #127 (simplification)

Dropping rename and add-prefix from libraries
Reported by:	Abdulaziz Ghuloum

Component:	libraries
Version:	5.91

One sentence summary: The add-prefix and rename forms in libraries'
import form are not necessary if local imports are provided.

Description: 

The syntax of the import form for R6RS libraries provides a way of
renaming and adding a prefix to imported identifiers. The rationale
for providing this facility is to minimize the chance of name
collision amongst identifiers imported from multiple libraries that
are written by many people. This is very likely to happen because all
(possibly thousands of) imported identifiers are dumped into the
library's global environment, making the chance for conflicts much
more likely. Making all identifiers longer by adding prefixes, or
manually renaming all conflicting identifiers is not the optimal
solution to the problem.

When local imports give the programmers the ability to control the
scope of the imported identifiers (possibly limiting the scope to a
single reference if needed), the programmer is unlikely to need having
all imported identifiers to have unique names. In my personal
experience using Chez Scheme's modules for years, I never for once
needed to add prefixes to imported identifiers.

Recommendation: 

The import form of R6RS libraries should be simplified by removing the
rename and add-prefix forms since these two facilities are an artifact
of the lack of scope control in current R6RS libraries.

RESPONSE:

Independent of whether local `import' really negates the usefulness of
prefixes, R6RS will not include local `import' (see the response to
formal comment 126). So, the current draft's motivation for prefixes
remains, and we believe that import prefixes should remain in R6RS.