Opened 6 years ago
Closed 4 years ago
#185 closed defect (wontfix)
Add sixth "centered" division operator
Reported by: | cowan | Owned by: | cowan |
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Priority: | major | Milestone: | |
Component: | WG1 - Core | Keywords: | |
Cc: |
Description
From the Guile manual:
— Scheme Procedure: centered/ x y
— Scheme Procedure: centered-quotient x y
— Scheme Procedure: centered-remainder x y
These procedures accept two real numbers x and y, where the divisor y must be non-zero. centered-quotient returns the integer q and centered-remainder returns the real number r such that x = q*y + r and -|y/2| <= r < |y/2|. centered/ returns both q and r, and is more efficient than computing each separately.
Note that centered-quotient returns x/y rounded to the nearest integer. When x/y lies exactly half-way between two integers, the tie is broken according to the sign of y. If y > 0, ties are rounded toward positive infinity, otherwise they are rounded toward negative infinity. This is a consequence of the requirement that -|y/2| <= r < |y/2|.
Note that these operators are equivalent to the R6RS operators div0, mod0, and div0-and-mod0.
--Andy Wingo
Change History (5)
comment:1 Changed 6 years ago by alexshinn
- Resolution set to fixed
- Status changed from new to closed
comment:2 Changed 6 years ago by cowan
- Resolution fixed deleted
- Status changed from closed to reopened
I'm reopening this ticket based on the arguments below:
AFAIU centered/ is useful when you want to restrict the range of the result of division to be a fixnum, which is useful when implementing Scheme. See http://lists.gnu.org/archive/html/guile-devel/2011-01/msg00136.html .
comment:3 Changed 6 years ago by cowan
- Status changed from reopened to decided
WG1 accepted this proposal.
comment:4 Changed 5 years ago by cowan
- Owner changed from alexshinn to cowan
- Status changed from decided to writing
comment:5 Changed 4 years ago by cowan
- Resolution set to wontfix
- Status changed from writing to closed
Undone by #278.
We voted not to include this.