pair method

@override LambdaBuilder pair()

The church pair.

Implementation

@override
LambdaBuilder pair() => LambdaBuilder.abstract(
      LambdaBuilder.abstract(
        LambdaBuilder.abstract(
          LambdaBuilder.applyAll(
            [
              LambdaBuilder.fromVar(name: 'z'),
              LambdaBuilder.fromVar(name: 'x'),
              LambdaBuilder.fromVar(name: 'y'),
            ],
          ),
          'z',
        ),
        'y',
      ),
      'x',
    );