[cfp-interest 3752] Rounding terminology

[Jim Thomas]

This note follows up on the action item

>     Group: Review the rounding direction language, with Jim to provide an email to kick things off.

This note describes and illustrates a potential process CFP might use to address inconsistencies in the terminology for rounding. The work below does not address the degree to which the inconsistencies are a significant problem for implementors or programmers.

Process: 
Search the draft for “rounding”. There are 271 instances in N3685. For each instance, ask whether the use is consistent with the understanding of the terms as noted below. If needed, propose a change.

Understanding of terms:
Rounding direction - method of rounding ("toward zero", “to nearest with ties to even”, ...)
Rounding direction mode - system variable whose values are rounding directions, sometimes used to refer to the value of the mode variable
Current rounding direction - value of applicable (constant or dynamic) rounding direction mode
Default rounding direction - rounding direction in the absence of any constant or dynamic mode change

The following application of the process should be taken as illustration. It needs to be checked and is not complete.

P5
Current rounding mode -> rounding direction

P26
Rounding mode -> rounding direction mode
Rounding mode -> rounding direction mode
Rounding ok

P27
To-nearest rounding ok
Roundings ok
To-nearest rounding ok
Roundings ok

P28
To-nearest rounding ok
Roundings ok

P29
To-nearest rounding ok
Translation-time rounding mode -> translation-time rounding direction

P30
Or as a constant rounding mode set by an FENV_ROUND pragma -> or set by an FENV_ROUND pragma

P63
Rounding ok
Rounding ok
Rounding direction ok
Or a constant rounding mode set by -> or set by
Default rounding ok
Default rounding ok
Default rounding ok
Rounding mode -> rounding direction mode
Default translation rounding-direction mode -> default translation rounding direction

P64
Default execution-time rounding ok
Rounding ok
Rounding ok
Rounding direction ok
Rounding to nearest ok
Rounding toward zero ok
Rounding toward positive infinity ok
Rounding toward negative infinity ok
Rounding ok
Default rounding -> default rounding direction

P74
Rounding errors ok

P75
Required rounding properties -> ???

P158
Rounding direction mode ok

P224
Dynamic rounding direction mode ok
Rounding-direction control modes ok

P225
Rounding directions ok
Rounding direction macros ok

P226
Dynamic rounding direction mode ok
Decimal rounding direction -> decimal rounding direction mode
Constant rounding direction modes ok
Dermal rounding direction mode ok
#15 and #16 must be harmonized with recent proposal for Annex F

P227
Constant rounding direction ok
Static rounding mode -> constant rounding direction mode
Rounding direction macros ok
Constant rounding mode ok
Dynamic rounding ok
Rounding ok
According to the mode -> according to the rounding direction
Dynamic rounding mode -> dynamic rounding mode value
Default rounding mode -> default rounding mode value
Constant rounding mode ok
Constant rounding mode ok

etc.


- Jim Thomas









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