📅 最后修改于: 2021-01-01 04:38:34 🧑 作者: Mango
可空运运算符用于处理数据库查询。它处理存储在表中代替数据的空值。
| Nullable on left | Nullable on right | Both sides Nullable |
|---|---|---|
| ?> | >? | ?>? |
| ?>= | >=? | ?>=? |
| ?<= | <=? | ?<=? |
| ?< | ?lt:? | |
| ?= | =? | ?=? |
| ?+ | +? | ?+? |
您可以对所有二进制算术和比较操作应用可为空的运算符。
| Operator | Associativity |
|---|---|
as |
right |
| when | right |
| |(pipe) | left |
| ; | right |
| let | nonassociative |
| function,fun,match,try | nonassociative |
| if | nonassociative |
| -> | right |
| := | right |
| , | nonassociative |
| or, || | left |
| &,&& | left |
| :>; , :?>; | right |
!=op, <op, >op, =, |op, &op, &
(including |
left |
^op (including ^^^) |
right |
| :: | right |
:? |
non associative |
-op, +op |
applies to infix uses of these symbols |
*op, /op, %op |
left |
**op |
right |
f x (function application) |
left |
| (pattern match) |
right |
prefix operators (+op, -op, %, %%, &, &&, !op, ~op) |
left |
| . | left |
f(x) |
left |
f<types> |
left |