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From "Daniel.Sun" <sun...@apache.org>
Subject [GEP]Lazy evaluation for Groovy 3
Date Sat, 17 Mar 2018 07:35:09 GMT
Hi all,

       Sometimes we do not want evaluate some expression eagerly(Maybe
evaluation is expensive), e.g. a table contains a field `records` whose
content is queried from DB, but we do not get the content of `records`
eagerly util we access `records`.

class SomeTable {
       def records = ( doQueryFromDB() )   // the expression in the
parentheses will be evaluated lazily
       def sum() {
             // access the methods or fields of `records`, trigger
evaluation, i.e. the query of DB
       }
       def getRecords() {
             return records // do NOT trigger evaluation
        }
}

         Lazy evaluation syntax is very simple( just supports 1) and 2) ):
1) def v = ( someExpression() )  // Lazy evaluation for variable declaration
2)  v = ( someExpression )          // Lazy evaluation for assignment
3)  println(( someExpression )) // NOT lazy evaluation

           Any thoughts?

Cheers,
Daniel.Sun



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