[r6rs-discuss] [Formal] SRFI-39 should be made an R6RS library

[John Cowan]

R. Kent Dybvig scripsit:

> Global parameters are typically but not always set once and forgotten; an
> application might change the collection parameters, for example, to suit
> different modes of operation.  It generally doesn't make sense to localize
> them, however, or they would be defined as thread parameters.

Why not just use ordinary Scheme top-level variables, then, and use
SET! to change them on the occasions when it might be required?
Why use separate machinery for them?

OT: I've noticed a tendency in Scheme libraries to eschew global value
definitions for functions that return a constant value.  Has anyone
else noticed this (I can't point to evidence offhand), and does anyone
know why?

> In contrast, a much wider range of parameters are thread parameters:  

[examples snipped]

That's the sort of thing I'd expect to use parameters for, when localizing
is important.

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