Wed, 08 Feb 2023 10:19:54 GMT

From: | anton@mips.complang.tuwien.ac.at (Anton Ertl) |

Newsgroups: | comp.compilers |

Date: | Wed, 08 Feb 2023 10:19:54 GMT |

Organization: | Institut fuer Computersprachen, Technische Universitaet Wien |

References: | 23-01-092 23-02-003 23-02-019 23-02-025 23-02-026 23-02-029 |

Injection-Info: | gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="11788"; mail-complaints-to="abuse@iecc.com" |

Keywords: | arithmetic, comment |

Posted-Date: | 08 Feb 2023 11:49:47 EST |

Hans-Peter Diettrich <DrDiettrich1@netscape.net> writes:

*>AFAIK use IEEE-754 floating point numbers still sign-magnitude*

*>representation.*

*>Then the same representation of integral numbers may have advantages in*

*>computations.*

Such as? Anyway, whatever these advantages may be, they have not been

enough to prevent the extermination of sign-magnitude integers.

*>[I presume the sign-magnitude is to enable the hidden bit trick,*

*>which doesn't apply in unscaled integers. -John]*

With a ones-complement or two's-complement mantissa the hidden bit

would just have the same sign as the sign bit, so this trick is not

tied to sign-magnitude representation.

Some years ago someone sketched a two's-complement representation for

FP (that also includes the exponent), but I did not quite get the

details. Anyway, I expect that whatever the advantages of that

representation are, they are not enough to justify the transition

cost.

- anton

--

M. Anton Ertl

anton@mips.complang.tuwien.ac.at

http://www.complang.tuwien.ac.at/anton/

[PDP-6/10 floating point was two's complement. As someone else recently noted, that

meant they could use fixed point compare instructions. -John]

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