bugLiberty Eiffel - Bugs: bug #39194, ROPE assumes lower=1

 
 

bug #39194: ROPE assumes lower=1

Submitted by:  Cyril Adrian <cadrian>
Submitted on:  Fri 07 Jun 2013 11:51:06 AM UTC  
 
Category: Kernel librariesSeverity: 3 - Normal
Priority: 5 - NormalStatus: Invalid
Assigned to: Paolo Redaelli <Tybor>Open/Closed: Closed
Release: adlerFixed Release: None
Planned Release: None

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Tue 30 Jul 2013 12:38:04 PM UTC, comment #1:

This bug is actually invalid since ABSTRACT_STRING clearly states that it is a "Character STRINGs indexed from `1' to `count'." and therefore defines "lower: INTEGER is 1".

My humble opinion is that code dealing with strings of text shall never makes any assumption of the actual value of lower.
In fact C strings set lower to 0 a manifest legacy optimization as comparing to zero has always been a fast operation even on CPU from seventies.

Removing the invariant "lower = 1" would allow to implement fixed substring of fixed strings using only a reference and two offsets.

Do you think it is worth at least a little debate?

Paolo Redaelli <Tybor>
Project AdministratorIn charge of this item.
Fri 07 Jun 2013 11:51:06 AM UTC, original submission:

https://github.com/LibertyEiffel/Liberty/issues/20

While it is customary that ABSTRACT_STRING.lower is 1 it is wiser to remove this assumption even on ROPE.

In fact we may want to change this invariant in future.

Cyril Adrian <cadrian>
Project Administrator

 

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  • -unavailable- added by Tybor (Posted a comment)
  • -unavailable- added by cadrian (Submitted the item)
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    Follow 3 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Tue 30 Jul 2013 12:38:04 PM UTCTyborStatusNone=>Invalid
      Open/ClosedOpen=>Closed
      ReleaseNone=>adler

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