SMath Studio Forum
»
SMath Studio
»
Bugs & Problems
»
Bug/Error in the execution of Range(3) function
 Rank: Newbie
Groups: Registered
Joined: 26/06/2012(UTC) Posts: 9  Location: Massachusetts
|
There's a problem with the Range(3) function. Here's an example: 1. Create a vector for a variable n using the range(3) function such as: n:=0.03, 0.0325.. 0.05 This should produce a vector with 9 elements ranging from 0.03 to 0.05 in 0.0025 increments. However, it actually produces an 8 element vector from 0.03 to 0.0475. It appears the last element (0.05) is truncated. Why? Thanks in advance, Brett
|
|
|
|
|
|
  Rank: Administration Groups: Registered, Advanced Member Joined: 23/06/2009(UTC) Posts: 1,740   Was thanked: 318 time(s) in 268 post(s)
|
Hello Brett, I think it is due to the machine floating point rounding error. Here is the possible explanation of it. n:range(0.03,0.05+10^{-16},0.0325) n=mat(0.03,0.0325,0.035,0.0375,0.04,0.0425,0.045,0.0475,0.05,9,1)Adding a rather small number to the last number (order of magnitude of computing precision ~15 decimal place) might solve this. Regards, Radovan Edited by user 29 November 2012 14:09:05(UTC)
| Reason: Not specified |
When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!" |
|
|
|
|
|
Rank: Newbie
Groups: Registered
Joined: 26/06/2012(UTC) Posts: 9 Location: Massachusetts
|
Thanks Radovan! That worked (though I'm somewhat concerned that an error like this popped up in the first place).
Brett
|
|
|
|
|
|
 Rank: Advanced Member Groups: Registered
Joined: 15/04/2012(UTC) Posts: 1,988  Was thanked: 1126 time(s) in 723 post(s)
|
I agree with Radovan that this feature is not exactly a bug. However, testing the loop exit condition with some tolerance halfway between the iterator increment and machine precision would be a default that might perhaps meet the intent of most users. Then ugly workarounds could be avoided.
|
|
|
|
|
|
|
Rank: Newbie
Groups: Registered
Joined: 26/06/2012(UTC) Posts: 9 Location: Massachusetts
|
I think the easiest (and perhaps cleaner) workaround is the alternate method I included in the attachment. By using a For loop with a dummy (integer) index variable (e.g., i) run through a range of 1 to 9, then under the For loop create the vector n in an equation using the index variable.
For i:=1..9
n:=0.03+(i-1)*0.0025
|
|
|
|
|
|
Rank: Advanced Member Groups: Registered
Joined: 15/04/2012(UTC) Posts: 1,988 Was thanked: 1126 time(s) in 723 post(s)
|
The same without for loop:
0.03+0.0025*(range(0,8))=mat(0.03,0.0325,0.035,0.0375,0.04,0.0425,0.045,0.0475,0.05,9,1)
Both versions of the workaround obfuscate the upper loop limit, that's why I would like the range(3) function to be modified. However, the workarounds make the iterator increment more obvious. Would perhaps be fine to have an alternative range(3) with range(start,stop,step) displaying as
start..stop by step |
|
 1 user thanked mkraska for this useful post.
|
|
|
|
 Rank: Advanced Member Groups: Registered, Advanced Member Joined: 13/01/2012(UTC) Posts: 2,648  Location: Italy Was thanked: 1331 time(s) in 876 post(s)
|
Originally Posted by: mkraska  The same without for loop:
0.03+0.0025*(range(0,8))=mat(0.03,0.0325,0.035,0.0375,0.04,0.0425,0.045,0.0475,0.05,9,1)
Both versions of the workaround obfuscate the upper loop limit, that's why I would like the range(3) function to be modified. However, the workarounds make the iterator increment more obvious. Would perhaps be fine to have an alternative range(3) with range(start,stop,step) displaying as
start..stop by step I agree with Martin  |
If you like my plugins consider to support SMath Studio buying a plan; to offer me a coffee: paypal.me/dcprojects |
|
|
|
|
|
SMath Studio Forum
»
SMath Studio
»
Bugs & Problems
»
Bug/Error in the execution of Range(3) function
Forum Jump
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.
