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comunica / sparqlee

⚙️ SPARQL expression evaluator library - Moved to @comunica/expression-evaluator
https://www.npmjs.com/package/sparqlee
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Document spec link explaining `arithmeticWidening` #107

Closed jitsedesmet closed 3 years ago

jitsedesmet commented 3 years ago

We should make sure we understand why we use arithmeticWidening and where this behaviour is mentioned in the specs. This issue has 2 tasks.

  1. Find the specs surounding arithmeticWidening.
  2. Implement arithmeticWidening like the specs sugest.

arithmeticWidening answers a simple question: what type is the return type of an arithmetic operation. things to consider: it could be that short + short \ne short. Example: is 240 + 100 still a short? It can not be represented as a short. Should we check this? Or do we need to return a short with value 340 which is not a valid short value.

jitsedesmet commented 3 years ago

Here's what I found: https://www.w3.org/TR/xpath20/#mapping .

[Definition: When referring to a type, the term numeric denotes the types xs:integer, xs:decimal, xs:float, and xs:double.] An operator whose operands and result are designated as numeric might be thought of as representing four operators, one for each of the numeric types. For example, the numeric + operator might be thought of as representing the following four operators:

With a table underneath it. I think this is a pretty good solution. It basically means type promotion will handle that problem.