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*To*: bartley%home%ti-csl.csnet@RELAY.CS.NET*Subject*: number syntax*From*: jinx@GENEVA.AI.MIT.EDU (Guillermo J. Rozas)*Date*: Thu, 9 Apr 87 19:11:01 est*Cc*: rrrs-authors@MC.LCS.MIT.EDU*In-Reply-To*: David Bartley's message of Thu, 9 Apr 87 16:19:28 cdt <8704092119.AA23970@home>

Has anyone implemented exactness using a mechanism substantially different from the one Kent Dybvig describes in his new book? (Quoting his page 111: "In practice, the internal representation for an exact quantity is as an integer or ratio, and the internal representation for an inexact quantity is as a floating point number, although other representations are possible." Also, "The exactness of a complex numeric object depends on the exactness of its real and imaginary parts.") How do people feel about this approach? Does this fulfill the spirit of exactness? Does anyone want to pay for a more orthogonal exactness attribute for numbers? That is very much against the proposal. We have not implemented it at MIT, but the original proposal is such that both exact and inexact flonums are possible (and desirable), and similarly for the other types. Although we have not implemented it, we have an implementation in mind, and it is orthogonal: for each type of number, there is a bit specifying whether it is exact or not. Is it permissible for an exact 3.5 to print (by default) as 7/2 or an inexact 2 to print as 2.0? It depends on the format specification. For the explicit ones, there should be no question. I think, however, that if the format is (HEUR) it should print as #i2 . Has anyone implemented the -1+2i or 5@7 syntax for complex numbers? Is there strong resistance to Common Lisp's #c(-1 2) representation? CPH has implemented the r^3rs complex notation for MIT Scheme. Having the #c notation should be optional. I don't think the syntax becomes ambiguous if it is added, but there is no need for it. In general, is there anyone strongly opposed to the idea that Scheme number representations should be made to look more like Common Lisp's? Not I, as long as it does not run counter to what the report already states.

**Follow-Ups**:**Re: number syntax***From:*willc%tekchips.tek.com@RELAY.CS.NET

**References**:**number syntax***From:*David Bartley <bartley%home%ti-csl.csnet@RELAY.CS.NET>

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