Re: [Chicken-users] set! on unbound variable

[John Cowan]

On Sat, Sep 24, 2016 at 11:39 AM, Dan Leslie <address@hidden> wrote:

It seems that Chicken has a parameter to enforce R5RS strictness:

> -r5rs-syntax disables the Chicken extensions to R5RS syntax

All that does is disable the syntax keywords that are normally available but are not part of R5RS, so it's not relevant here.  In any case, R5RS does allow the approach Chicken takes to unknown variables.  Section 5.2.1. says:

Some implementations of Scheme use an initial environment in which all possible variables are bound to locations, most of which contain undefined values. Top level definitions in such an implementation are truly equivalent to assignments.

See http://trac.sacrideo.us/wg/wiki/SetUndefinedVariable for which Schemes do this

and which do not.

-- 

John Cowan          http://vrici.lojban.org/~cowan        address@hidden

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