!=

Set a value using a lens into state. Forces both the value and the whole state.
Fulfill a promise. Each promise should only be fulfilled once.
>>> runLazy_ $ \p -> p != "good"
"good"
>>> runLazy_ $ \p -> do q <- promise_; p != "yay! " ++ demand q; q != "it works."
"yay! it works."
>>> runLazy_ $ \p -> return ()
*** Exception: BrokenPromise
>>> runLazy (\p -> return ()) "default"
"default"
Non-equality check.

Examples

selectSimon :: MonadIO m => ReaderT SqlBackend m [Entity User]
selectSimon = selectList [UserName !=. "SPJ" ] []
The above query when applied on dataset-1, will produce this:
+-----+-----+-----+
|id   |name |age  |
+-----+-----+-----+
|2    |Simon|41   |
+-----+-----+-----+
Equality == lifted over errorToLeft
> 1 `div` 1  !==!  2 `div` 2
True
> 1 `div` 1  !==!  1 `div` 2
False
> 1 `div` 1  !==!  1 `div` 0
False
> 6 `mod` 0  !==!  2 `div` 0
True
> head []  !==!  tail []
False
> error "a"  !==!  error "a"
True
> error "a"  !==!  error "b"
False
On error, this function returns the result of comparing the first line of error values.
The connective between route patterns and the handler that parses the body, which allows post params to be extracted with param and allows file to work (otherwise, it will trigger a runtime error).
Helper for use in combination with .:? to provide default values for optional JSON object fields. This combinator is most useful if the key and value can be absent from an object without affecting its validity and we know a default value to assign in that case. If the key and value are mandatory, use .: instead. Example usage:
v1 <- o .:? "opt_field_with_dfl" .!= "default_val"
v2 <- o .:  "mandatory_field"
v3 <- o .:? "opt_field2"
Strictly modify a field of the state.
Strictly modify a field of the state.