Re: CLTL compatible type contagion?

[Raymond Toy <toy@rtp.ericsson.se>]

>>>>> "Bruno" == Bruno Haible <haible@ilog.ilog.fr> writes:


    Bruno> Raymond Toy writes:
    >> 
    >> (+ 1d50 1.0)
    >> 
    >> does not return 1d50.  Instead, it signals a floating-point
    >> overflow.  I presume that clisp does the addition in

[nice example of why clisp does it this way deleted]

    Bruno> then of course the implementation shall do its best to
    Bruno> guarantee that if the arguments of the function `+' satisfy
    Bruno> this assumption, then the result of (+ 1d40 1e37) satisfies
    Bruno> this assumption as well. If it can't, I prefer to see an
    Bruno> error.

By your example, (+ 1d40 1e37) does not satisfy the assumption right?
Should clisp then signal an error?  

I don't know what the "right" answer would be.  At times I like
promoting to the bigger type, but at other times, I like instantly
seeing when I've lost precision in clisp.

However, I have discovered the "errant" part of my program.  I lose
precision because I had something like

	(sqrt 22/7)

and clisp returned a float value.  I guess the result would depend on
whether 22/7 has infinite precision/accuracy in which case the answer
should be a long-float (?) or whether 22/7 has accuracy of +/- 1/14 in
which case the answer should be short-float or less.  The assumption
that 22/7 is a single-float is a bit hazy.

Ray