reduce函数

    在openCypher中，reduce()函数没有定义。nGQL使用了Cypher方式实现reduce()函数。

    1. nebula> RETURN reduce(totalNum = 10, n IN range(1, 3) | totalNum + n) AS r;
    2. +----+
    3. | r  |
    4. +----+
    5. | 16 |
    6. +----+
    8. nebula> RETURN reduce(totalNum = -4 * 5, n IN [1, 2] | totalNum + n * 2) AS r;
    9. +-----+
    10. | r   |
    12. | -14 |
    14. nebula> MATCH p = (n:player{name:"LeBron James"})<-[:follow]-(m) \
    15.         RETURN  nodes(p)[0].age AS src1,  nodes(p)[1].age AS dst2,  \
    16.         reduce(totalAge = 100, n IN nodes(p) | totalAge + n.age) AS sum;
    17. +------+------+-----+
    18. | src1 | dst2 | sum |
    19. +------+------+-----+
    20. | 34   | 31   | 165 |
    21. +------+------+-----+
    22. | 34   | 29   | 163 |
    23. +------+------+-----+
    24. | 34   | 33   | 167 |
    25. +------+------+-----+
    26. | 34   | 26   | 160 |
    28. +------+------+-----+
    29. | 34   | 37   | 171 |
    30. +------+------+-----+
    32. nebula> LOOKUP ON player WHERE player.name == "Tony Parker" \
    33.         |  GO FROM $-.VertexID over follow \
    34.         WHERE follow.degree != reduce(totalNum = 5, n IN range(1, 3) | $$.player.age + totalNum + n) \
    35.         YIELD $$.player.name AS id, $$.player.age AS age, follow.degree AS degree;
    36. +---------------------+-----+--------+
    37. | id                  | age | degree |
    38. +---------------------+-----+--------+
    39. | "Tim Duncan"        | 42  | 95     |
    40. +---------------------+-----+--------+
    41. | "LaMarcus Aldridge" | 33  | 90     |
    42. +---------------------+-----+--------+
    43. +---------------------+-----+--------+