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Date: Mon, 22 Oct 2012 04:46:09 -0700 (PDT)
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Subject: Duplicate identifiers in let - difference between CL and Scheme
From: jurgen_defurne <jurgen.defu...@pandora.be>
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Hello,

While trying out some things, I noticed there is a big difference in interp=
retation between CL and Scheme for the following expression:

(let ((a 100)
      (a 200))
  (print a)) ;;e.g.

In Common Lisp the value 200 is printed, in Scheme an error occurs.

Is this for backwards compatibility of CL with older Lisps, is this to make=
 it easier to implement, or are there other reasons?

I must say that I have already written some programs in Common Lisp, some n=
ot so easy, e.g. a simulation of microprocessor on the signal level, and I =
have not had the problem that I by accident created variables with almost t=
he same name, and then had typos. Common Lisp invites for a strong decompos=
ition, which together with almost no restrictions on identifiers, lowers th=
e chance of name clashes.

Taking it then from the Scheme side: is there advantage in detecting name c=
lashes, aside from it being part of the Scheme standard?

Regards,

Jurgen