Added support for specifying the sort order in SPARQL::Client::Query.order()

[ckristo]

Hi,

based on a short discussion (issue #60) -- I added support for specifying the sort order direction with sparql-client's query DSL ::

• query.order(:var1 => :asc, :var2 => :desc)
• query.order([:var1, :asc], [:var2, :desc])

Both -- Arrays and Hashes are supported as arguments. If not both should be supported, I will remove one of them.

Cheers, Chris

[gkellogg]

I'll look at this, but we should also have #desc and #asc methods to keep with the spirit of the DSL.

[ckristo]

@gkellogg something like query.order(asc(:o), desc(:p)) or query.order(:o).asc().order(:p).desc()?

[gkellogg]

The SPARQL Grammar is:

    [23]  OrderClause             ::= 'ORDER' 'BY' OrderCondition+
    [24]  OrderCondition          ::= ( ( 'ASC' | 'DESC' ) BrackettedExpression )
                                    | ( Constraint | Var )

So, it problable need to include things such as:

• query.order(:o)
• query.order.asc(:o)
• query.order.desc(:s).asc(:o)

where order(:c) is a variable, and the arguments to asc and desc are also just variables. Trying to do a BracketedExpression or Constraint would be beyond the scope of the DSL. order.asc(:s) would be equivalent to asc(:s), or even just order(:s), as ASC is the default. order(:s, desc: true) or order(s: :desc) is also reasonable. Adding more variables could loose order, but Ruby 2+ preserves order in hashes, so it's probably also reasonable.

[ckristo]

Hashes preserve ordering since Ruby 1.9 -- I've checked that before implementing the PR (cf. 1

And as far as I remeber, sparql-client requires ruby 1.9, right?

Chris

On 27 Aug 2015, at 00:20, Gregg Kellogg notifications@github.com wrote:

I'll look at this, but we should also have #desc and #asc methods to keep with the spirit of the DSL.

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