Map and Filter Algorithms

Easylambda’s predicate function objects consist of logical operations like eq (equals to), gt (greater than) etc. These can be combined with the relational operators &&, || or !. The predicates can take multiple values for comparison with multiple columns e.g. filter<3,2>(gt(7.0, 4)) filters the rows with third column greater than $7.0$ and second column greater than $4$. The logical function objects have column selection for a single column e.g. gt<3>(7.0) && !et<1>('a') creates a predicate that checks for third column be greater than 7.0 and the first column not be equal to ‘a’.

Special algorithms for merging array columns and for exploding arrays are available to the map unit. In addition, the map unit can generally use algorithms from the C++ standard library.

Following are the function object names available. Check demoMapFilter for usage examples of these function objects.

Map

• mergeAr

• explodeAr

• addSerialNo

Filter

• eq
• neq
• gt
• lt
• eqAr
• neqAr
• gtAr
• ltAr
• tautology