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Difference between revisions of "Datatypes R2 Issue 65"
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| Line 5: | Line 5: | ||
[from Charlie] | [from Charlie] | ||
| − | There is an error in the abstract datatypes that is not helping us | + | There is an error in the abstract datatypes that is not helping us here |
| − | + | ||
| − | + | invariant(IVL<T> x) | |
| − | + | where x.low.isNull.or(x.high.isNull) { | |
| − | + | x.center.notApplicable; | |
| − | + | }; | |
| − | + | ||
| − | > x) | + | This cannot be true -- since center is used exactly when high and low are unknown (ie null). |
| − | + | I think that this should be | |
| − | + | ||
| − | + | invariant(IVL<T> x) | |
| + | where x.low.isNull.xor(x.high.isNull) { | ||
| + | x.center.notApplicable; | ||
| + | }; | ||
| + | |||
| + | [end] | ||
| + | |||
| + | :I think both statements do not belong in the abstract spec. I vote for removing this. (Grahame agreed) [[User:Gschadow|Gschadow]] 22:30, 11 January 2007 (CST) | ||
| + | |||
| + | :As a side note: if you truly don't know any of low, high, or center, then you probably do not know the center. However, in some cases you want to say: "I don't know when it started nor when it ended, but I know at time t it was there. What to do about that? [[User:Gschadow|Gschadow]] 22:30, 11 January 2007 (CST) | ||
== Discussion == | == Discussion == | ||
Revision as of 04:30, 12 January 2007
Contents
Data Types Issue 65: IVL low/high and center/width issue
Introduction
[from Charlie]
There is an error in the abstract datatypes that is not helping us here
invariant(IVL<T> x)
where x.low.isNull.or(x.high.isNull) {
x.center.notApplicable;
};
This cannot be true -- since center is used exactly when high and low are unknown (ie null). I think that this should be
invariant(IVL<T> x)
where x.low.isNull.xor(x.high.isNull) {
x.center.notApplicable;
};
[end]
- I think both statements do not belong in the abstract spec. I vote for removing this. (Grahame agreed) Gschadow 22:30, 11 January 2007 (CST)
- As a side note: if you truly don't know any of low, high, or center, then you probably do not know the center. However, in some cases you want to say: "I don't know when it started nor when it ended, but I know at time t it was there. What to do about that? Gschadow 22:30, 11 January 2007 (CST)
Discussion
Links
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