Mailing List Archive: 49091 messages

# Rounding

### [1/7] from: mat:0wnerage at: 29-May-2002 18:54

Librarian comment

the round function is supplied as standard in REBOL 1.3 and later.

Folks,
>> print to-integer 1.6
1 I can't for the life of me find a word which does the same as this but which actually rounds (so you'd get 2) rather than just chopping off the remainder. Is there such a beast or must one write a function to do it? I've actually resorted to doing exactly this and it's pretty ugly :) Regards, Mat

### [2/7] from: greggirwin:mindspring at: 29-May-2002 12:57

Hi Mat, Here's a rounding function that might do what you want. Watch for word-wrap! ; Ladislav Mecir, Gregg Irwin (minor adjustment) mod: func [ {Compute a remainder.} value1 [number! money! time!] {The dividend} value2 [number! money! time!] {The divisor} /euclid {Compute a non-negative remainder such that: a = qb + r and r < b} /local r ] [ either euclid [ either negative? r: value1 // value2 [r + abs value2] [r] ;-- Alternate implementation ;value1 // value2 + (value2: abs value2) // value2 ][ value1 // value2 ] ] ;-- Note: to-interval does mod-like rounding. If the interval you ; specify is not evenly divisble into your base, the result ; may not be what you expect. E.g. round/to-interval 133 30 ; will round to 120, not 130, because 120 is an even multiple ; (read interval) of 30. ; Ladislav Mecir, Gregg Irwin round: func [ {Rounds numeric value with refinements for what kind of rounding you want performed, how many decimal places to round to, etc.} value [number! money! time!] {The value to round} /up {Round away from 0} /floor {Round towards the next more negative digit} /ceiling {Round towards the next more positive digit} /truncate {Remaining digits are unchanged. (a.k.a. down)} /places {The number of decimal places to keep} pl [integer!] /to-interval {Round to the nearest multiple of interval} interval [number! money! time!] /local factor ][ ;-- places and to-interval are redundant. E.g.: ; places 2 = to-interval .01 ; to-interval is more flexible so I may dump places. ;-- This sets factor in one line, under 80 chars, but is it clearer? ;factor: either places [10 ** (- pl)][either to-interval [interval][1]] factor: either places [ 10 ** (negate pl) ] [ either to-interval [interval] [1] ] ;-- We may set truncate, floor, or ceiling in this 'if block. if not any [up floor ceiling truncate] [ ;-- Default rounding is even. Should we take the specified ; decimal places into account when rounding? We do at the ; moment. either (abs value // factor) <> (.5 * factor) [ value: (.5 * factor) + value return value - mod/euclid value factor ] [ ;-- If we get here, it means we're rounding off exactly ; .5 (at the final decimal position that is). either even? value [ truncate: true ] [ either negative? value [floor: true][ceiling: true] ] ] ] if up [either negative? value [floor: true][ceiling: true]] if truncate [return value - (value // factor)] if floor [return value - mod/euclid value factor] if ceiling [return value + mod/euclid (negate value) factor] ] --Gregg

### [3/7] from: chris:ross-gill at: 29-May-2002 14:58

Hi Mat,
> >> print to-integer 1.6 > 1
I don't know of one, but here's my own: round: func [ dec [integer! decimal!] /local int ][ if 0.5 <= (dec - int: to-integer dec) [int: int + 1] int ] - Chris

### [4/7] from: chris:langreiter at: 29-May-2002 21:02

> Is there such a beast or must one write a function to do it?
round: func [x] [to-integer .5 + x] Enjoy ;-)

### [5/7] from: mat:0wnerage at: 30-May-2002 8:43

Hi Christian,
>> Is there such a beast or must one write a function to do it?
Christian> round: func [x] [to-integer .5 + x] Haha, yes. :) Could not see the wood for the trees. I should show you my version for comedy, I was using string manipulation to get the digits after the decimal. <blush> Regards, Mat.

### [6/7] from: rpgwriter:ya:hoo at: 30-May-2002 18:50

--- Mat Bettinson <[mat--0wnerage--com]> wrote:
> Folks, > >> print to-integer 1.6
<<quoted lines omitted: 6>>
> Is there such a beast or must one write a function > to do it?
I don't think there is one, but it shouldn't be too ugly. Rounding fractions >=0.5 away from 0, do this: round-off: func [ x [number!] ] [ return either greater? x 0 [ to-integer x + 0.5 ] [ to-integer x - 0.5 ] ]

### [7/7] from: rpgwriter::yahoo::com at: 30-May-2002 18:52

--- Christian Langreiter <[chris--langreiter--com]> wrote:
> > Is there such a beast or must one write a function > to do it? > > round: func [x] [to-integer .5 + x]
This has results which are probably undesired with negative inputs. Chris Dicely

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