[Development] Adding support for version number comparisons

[Keith Gardner]

On Sat, May 31, 2014 at 2:09 PM, Jake Petroules <
jake.petroules at petroules.com> wrote:

> On 2014-05-31, at 03:00 PM, Thiago Macieira <thiago.macieira at intel.com>
> wrote:
>
> Em sex 09 maio 2014, às 11:36:08, Keith Gardner escreveu:
>
> I have been working on adding a class to QtCore (QVersion) to support
> storing version numbers, convert to/from QString, and having comparison
> operators.  My goal was to provide an API to assist in the following use
> cases:
>
>   - Plugin loading where there are multiple versions on the same system.
>   - File format validation.
>   - Executing an already installed command line application where the
>   behavior is dependent on the called application's version.
>   - Performing software installations and updates.
>   - QMake support for version number comparisons.
>
> Please share other potential use cases where this might be useful.
>
>
> Ok, since we can't seem to agree, let's settle on the maximum common
> denominator: QVersion will only compare the numeric part of a version
> number.
> By default, two versions with the same numeric part will compare equally,
> regardless of any suffixes that may be present.
>
> Therefore, by default, given:
> QVersion a("5.3.0");
> QVersion b("5.3.0pl1");
> QVersion c("5.3.0beta1");
>
> a != b != c; // since they aren't equal
>
>
> This seems to contradict your previous statement, unless you're speaking
> conceptually here.
>
> To confirm, as far as the code goes, ((QVersion("5.3.0pl1") ==
> QVersion("5.3.0beta1")) === true), yes?
>
>
> QVersion::compare(a, b) == 0;
> QVersion::compare(b, c) == 0;
>
> We will also provide an overload for the QVersion::compare function taking
> a
> functor:
>
> template <typename SuffixCompare> static inline int
> compare(const QVersion &a, const QVersion &b, SuffixCompare suffixCompare)
> {
>  int cmp = compare(a, b);
>  if (cmp)
>  return cmp;
>  return suffixCompare(a.suffix(), b.suffix());
> }
>
> Thus, if you want to implement a comparison like OpenSSL's, you can do:
>
> QVersion::compare(a, b,
>     [](auto a, auto b) {
>  return QString::compare(a, b, Qt::CaseInsensitive);
>     });
>
> If you want a more complex comparison like I had wanted, you'd do:
>
> static int priorityOrder(const QString &suffix)
> {
> if (suffix.isEmpty())
>  return 0;
> return suffix.startsWith("alpha") || suffix.startsWith("beta") ||
>  suffix.startsWith("rc") ? -1 : 1;
> }
>
> static int myCompare(const QString &a, const QString &b)
> {
> int a_prio = priorityOrder(a);
> int b_prio = priorityOrder(b);
> if (a_prio != b_prio || a_prio == 0)
>  return a_prio - b_prio;
> return QString::compare(a, b, Qt::CaseInsensitive);
> }
>
> And then you'd use: QVersion::compare(a, b, myCompare);
>
>
> Big +1 to everything. This approach should serve everyones' use cases;
> let's get this integration rolling.
>

I can agree to that.  I will have an update this weekend with this spec.
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