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## Re: [PATCH] New module to perform decimal floating point arithmetic for

**From**: |
Ben Pfaff |

**Subject**: |
Re: [PATCH] New module to perform decimal floating point arithmetic for charts. |

**Date**: |
Tue, 13 Jan 2015 21:24:37 -0800 |

**User-agent**: |
Mutt/1.5.23 (2014-03-12) |

On Tue, Jan 13, 2015 at 07:03:17AM +0100, John Darrington wrote:
>* This change adds a small module to perform floating point arithmetic*
>* with a decimal base, and uses it to calculate the graticule marks for*
>* charts.*
>* *
>* Rationale: Graticule marks want to be displayed in decimal. However*
>* not all decimal values can be represented in a double precision*
>* floating point binary. This approach pushes the precision loss from*
>* the value of the mark, to the position on the chart - we don't*
>* particularly care if a tick mark is a fraction of a pixel out of place,*
>* but we do care if 4.0 is displayed as 3.9999999999*
Can you say a few words about the assumptions? At first glance, some of
the functions seem to suffer from catastrophic loss of precision upon
integer overflow, e.g. doesn't that happen in decimal_multiply() if the
intermediate result is greater than ORD_MAX? (Is some kind of care
taken to make sure that this cannot happen?)