[erlang-questions] feedback on my solutions to programming erlang second edition

Richard A. O'Keefe ok@REDACTED
Tue Aug 18 05:01:34 CEST 2015

On 17/08/2015, at 10:38 pm, Garrett Smith <g@REDACTED> wrote:
> I wonder why stack variables aren't included in stack traces - I've
> never seen that in any language (Richard? :) but it would be
> fantastically useful.

Burroughs MCP: stack *traces* were just a list of lines,
basically, but stack *dumps* showed you details (and since
the B6700 was a tagged machine, it could do a darned good
job of decoding stuff).

The Edinburgh EMAS operating system:  when an IMP (the EMAS
equivalent of C, sort of Algolish) program crashed, you got
a stack dump telling you about variables.  As a user, I was
quite annoyed by this, because of course the internals of a 
program I didn't have the source for were meaningless to me.

Neither of these provided stack traces (or dumps) *to programs*
as a data structure.  It's not clear what a program could *do*
with names and values of variables, considering that the
internal structure of a function can be changed dramatically
while still being the same interface.

In Smalltalk, an exception handler gets full access to
*everything*, because Smalltalk programs have full access
to everything in the stack anyway.  (Start with 'thisContext',
which is the executing frame, and proceed from there.  It's
not in the standard, thankfully.)

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