Erlang Central

Difference between revisions of "Floating Point Rounding"

From ErlangCentral Wiki

m
m (Reverted edits by Kaiserpanda (Talk); changed back to last version by Ayrnieu)
Line 56: Line 56:
  
 
[[Category:CookBook]][[Category:NumberRecipes]]
 
[[Category:CookBook]][[Category:NumberRecipes]]
 
 
 
[http://www.casino-web-gambling.com/blackjack-tips/blackjack-hints.html blackjack hints]
 
[http://www.gambling-online-theory.com/online-casino/online-casino-for-cash.html online casino for cash]
 
[http://www.casino-games-wiki.com/index.php/casino_games_online casino games online]
 
[http://www.casino-theory.com/online-casino-bonus/free-online-casino-tournament.html free online casino tournament]
 
[http://www.casino-theory.com/online-casino-bonus/free-online-casino-tournament.html free online casino tournament]
 
[http://www.gambling-online-theory.com/casinos-portal/internet-casinos-sites.html internet casinos sites]
 
[http://www.casino-games-wiki.com/index.php/play_casino_games_games_online play casino games games online]
 
[http://www.casinos-go.com/online-casino-tips/index.html online casino tips]
 
[http://www.gambling-online-theory.com/casinos-portal/index.html casinos portal]
 
[http://www.gambling-online-theory.com/casinos-portal/casinos-games.html casinos games]
 

Revision as of 08:50, 4 December 2006

Problem

You need to round a floating-point number to an integer.

Solution

Use one of the functions round/1, ceiling/1, floor/1 and trunc/1. Note, the standard Erlang distribution does not come with either floor/1 or ceiling/1, but they can be easily implemented in terms of trunc/1

floor(X) ->
    T = trunc(X),
    case X - T < 0 of
        true -> T - 1;
        false -> T
    end.

ceiling(X) ->
    T = trunc(X),
    case X - T < 0 of
        true -> T;
        false -> T + 1
    end.

1> floor(-4.3).
-5
2> ceiling(-4.3).
-4
3> trunc(-4.3).
-4
4> round(-4.3).
-4
5> floor(3.5).
3
6> ceiling(3.5).
4
7> trunc(3.5).
3
8> round(3.5).
4
9> round(7).
7

The procedures all return integers.

round/1 returns the closest integer to x, rounding to even when x is halfway between two integers. floor/1 returns the largest integer not larger than x. ceiling/1 returns the smallest integer not smaller than x. trunc/1 returns the integer closest to x whose absolute value is not larger than the absolute value of x.

Further general information on math and rounding is available from:

MathWorld definition of the Floor Function. MathWorld definition of the Ceiling Function