"I think the point is to get nil if x does not satisfy some predicate." <--
exactly.
I basically want something like `if-let`, but which returns x instead of
f(x). `(if-let [m-with-k (contains? m k)]...` results in `m-with-k`
evaluating to `true`, not `m`. I *think* it's better to reject something
that doesn't meet your criteria early, as opposed to guarding against not
accidentally doing something like `(.toUpper {:foo m})` and getting an
error every step of the way.
But like I said, I'm totally willing to believe there's a more
idiomatic/appropriate way of doing things.
On Friday, October 24, 2014 4:59:33 AM UTC-4, Gary Verhaegen wrote:
>
> I think the point is to get nil if x does not satisfy some predicate.
>
> The best option would depend on the context in which these expressions are
> used, but one option would be to write your predicates to return the input
> as the truthy value (and nil otherwise).
>
> On Friday, 24 October 2014, Laurens Van Houtven <[email protected]> wrote:
>
>> Hi Sam,
>>
>>
>> I’m not sure I understand. If not for sequences, then what for? `(if
>> (pred x) x)` looks like it’s missing an else-clause; so I don’t know what
>> happens when (not (pred x)).
>>
>> From the rest of your e-mail it sounds a little bit like you might want
>> (get m x x)? (i.e. get me x if x isn’t in m; otherwise give me the value
>> mapped to x in m).
>>
>>
>> hth
>> lvh
>>
>>
>> On 24 Oct 2014, at 06:06, Sam Raker <[email protected]> wrote:
>>
>> > Is there anything simpler/more idiomatic than `(if (pred x) x)`? What I
>> really want is something better than `(if (= (get a-map a-key) a-val)
>> a-map)`/`(if (= (get-in a-map some-keys) a-val) a-map)`, but that might be
>> too specific to have been 'cached' somewhere.
>> >
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