Re: docstrings of if-let and when-let incorrect

[Aaron Cohen]

On Mon, May 21, 2012 at 1:43 PM, Jay Fields  wrote:

> There's a few issues there, first of which is that the code doesn't
> evaluate to what's shown:
> REPL started; server listening on localhost port 21867
> user=>
> (if-let [a 1]
>(if-let [b 2]
>   (if-let [c nil]
>   [a b c]
>   [a b c])
>   [a b c])
>[a b c])
> java.lang.Exception: Unable to resolve symbol: c in this context
> (NO_SOURCE_FILE:3)
>
> The c isn't nil in the else form, it's unbound. The same would be true if
> it failed at any of the other levels, if the original if fails, a, b, & c
> are all unbound. So, setting them to nil isn't consistent. It might be a
> good option, but it's not consistent with the code above. I can't imagine
> that you'd want the else statement to have a bunch of possibly nil vars for
> any reason other than printing - otherwise you'd end up putting a bunch of
> conditional logic in the else to know which vars are nil, in which case
> you're better off using nested if-lets anyway. But, maybe the printing
> (i.e. logging) scenario is reason enough to bind these variables. I'd
> probably lean towards keeping them all unbound, as it's clear that each var
> would be bound (if form) or unbound (else form), versus each var being
> possibly truthy or nil in the else form.
>
>
Yeah, I was typing theory code. However, "none defined in the else" doesn't
fully match the "nested if-lets" behavior either. In the second if-let
stanza, "a" would be bound in the else case.

In any event, this is all just bike-shedding and illustrating that what
appears "obvious" isn't necessarily.

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Re: docstrings of if-let and when-let incorrect

[Jay Fields]

There's a few issues there, first of which is that the code doesn't
evaluate to what's shown:
REPL started; server listening on localhost port 21867
user=>
(if-let [a 1]
   (if-let [b 2]
  (if-let [c nil]
  [a b c]
  [a b c])
  [a b c])
   [a b c])
java.lang.Exception: Unable to resolve symbol: c in this context
(NO_SOURCE_FILE:3)

The c isn't nil in the else form, it's unbound. The same would be true if
it failed at any of the other levels, if the original if fails, a, b, & c
are all unbound. So, setting them to nil isn't consistent. It might be a
good option, but it's not consistent with the code above. I can't imagine
that you'd want the else statement to have a bunch of possibly nil vars for
any reason other than printing - otherwise you'd end up putting a bunch of
conditional logic in the else to know which vars are nil, in which case
you're better off using nested if-lets anyway. But, maybe the printing
(i.e. logging) scenario is reason enough to bind these variables. I'd
probably lean towards keeping them all unbound, as it's clear that each var
would be bound (if form) or unbound (else form), versus each var being
possibly truthy or nil in the else form.

But, I don't feel strongly either way.

On Mon, May 21, 2012 at 1:32 PM, Borkdude  wrote:

> I guess it wouldn't hurt having them available in the else, even if people
> won't use them often.
>
> On Monday, May 21, 2012 7:11:05 PM UTC+2, Aaron Cohen wrote:
>>
>> On Wed, May 16, 2012 at 9:53 AM, Walter Tetzner <
>> robot.ninja.saus...@gmail.com**> wrote:
>>
>>> On Wednesday, May 16, 2012 9:16:29 AM UTC-4, Aaron Cohen wrote:

 Saying something is obvious and then using the word monad a paragraph
 later is contradictory. ;)

 What should happen on the else branch of the if-let; which bindings are
 in scope and what would be their values?


>>> None of the bindings should be available in the else branch, since there
>>> would be no way to know which will succeed before run-time.
>>>
>>
>> I actually think that having all the bindings available and just nil for
>> everything past the first failure would be more useful, and also matches
>> the intuition that it expands out to nested if-lets
>>
>> (if-let [a 1 b 2 c nil] [a b c])
>>
>>
>> (if-let [a 1]
>>(if-let [b 2]
>>   (if-let [c nil]
>>   [a b c]
>>   [a b c])
>>   [a b c])
>>[a b c])
>>
>> => [1 2 nil]
>>
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Re: docstrings of if-let and when-let incorrect

[Borkdude]

I guess it wouldn't hurt having them available in the else, even if people 
won't use them often.

On Monday, May 21, 2012 7:11:05 PM UTC+2, Aaron Cohen wrote:
>
> On Wed, May 16, 2012 at 9:53 AM, Walter Tetzner <
> robot.ninja.saus...@gmail.com> wrote:
>
>> On Wednesday, May 16, 2012 9:16:29 AM UTC-4, Aaron Cohen wrote:
>>>
>>> Saying something is obvious and then using the word monad a paragraph 
>>> later is contradictory. ;)
>>>
>>> What should happen on the else branch of the if-let; which bindings are 
>>> in scope and what would be their values?
>>>
>>>
>> None of the bindings should be available in the else branch, since there 
>> would be no way to know which will succeed before run-time.
>>
>
> I actually think that having all the bindings available and just nil for 
> everything past the first failure would be more useful, and also matches 
> the intuition that it expands out to nested if-lets
>
> (if-let [a 1 b 2 c nil] [a b c])
>
>
> (if-let [a 1]
>(if-let [b 2]
>   (if-let [c nil]
>   [a b c]
>   [a b c])
>   [a b c])
>[a b c])
>
> => [1 2 nil] 
>

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Re: docstrings of if-let and when-let incorrect

[Aaron Cohen]

On Wed, May 16, 2012 at 9:53 AM, Walter Tetzner <
robot.ninja.saus...@gmail.com> wrote:

> On Wednesday, May 16, 2012 9:16:29 AM UTC-4, Aaron Cohen wrote:
>>
>> Saying something is obvious and then using the word monad a paragraph
>> later is contradictory. ;)
>>
>> What should happen on the else branch of the if-let; which bindings are
>> in scope and what would be their values?
>>
>>
> None of the bindings should be available in the else branch, since there
> would be no way to know which will succeed before run-time.
>

I actually think that having all the bindings available and just nil for
everything past the first failure would be more useful, and also matches
the intuition that it expands out to nested if-lets

(if-let [a 1 b 2 c nil] [a b c])


(if-let [a 1]
   (if-let [b 2]
  (if-let [c nil]
  [a b c]
  [a b c])
  [a b c])
   [a b c])

=> [1 2 nil]

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Re: docstrings of if-let and when-let incorrect

[Borkdude]

Wow, the discussion continued! 

I agree on what most people have said: AND-combined and none of the 
bindings available in the else.

On Friday, May 18, 2012 7:20:06 AM UTC+2, FrankS wrote:
>
> Christophe Grand was "experimenting" with some extensions to if-let and 
> when-let that had implicit ANDs for the let-forms: 
>
>
> https://github.com/cgrand/parsley/blob/master/src/net/cgrand/parsley/util.clj 
>
> It feels intuitive to me to allow multiple if-let-forms like cgrand 
> implements, and I can certainly remember situations where I could have used 
> such a feature. 
>
> -FrankS. 
>
>
>
> On May 16, 2012, at 11:26 AM, dgrnbrg wrote: 
>
> > I too assumed that if/when-let would support multiple bindings, short- 
> > circuiting if one failed, when I started learning Clojure. It seems 
> > that short-circuiting multiple bindings isn't surprising. 
> > 
> > On May 16, 10:56 am, Jay Fields  wrote: 
> >> I've also attempted to use if/when-let with multiple bindings in the 
> past. 
> >> I assumed that it would behave as 'AND' and that no bindings would be 
> >> available in 'else' 
> >> 
> >> Cheers, Jay 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> On Wed, May 16, 2012 at 10:29 AM, Dan Cross  wrote: 
> >>> On Wed, May 16, 2012 at 9:16 AM, Aaron Cohen  
> wrote: 
>  On Wed, May 16, 2012 at 9:10 AM, Walter Tetzner < 
> >>> robot.ninja.saus...@gmail.com> wrote: 
> > To make the bindings work like let, where later bindings can see 
> >>> previous 
> > bindings, I think the most natural way to do it is to have the 
> bindings 
> > behave like the maybe monad. 
> > [...] 
> >> 
>  Saying something is obvious and then using the word monad a paragraph 
> >>> later 
>  is contradictory. ;) 
> >> 
> >>> Hypothetically, "this is obvious, unlike most monads."  Zing! 
> >> 
>  What should happen on the else branch of the if-let; which bindings 
> are 
> >>> in 
>  scope and what would be their values? 
> >> 
> >>> None of the bindings should be in scope. 
> >> 
> >>>- Dan C. 
> >> 
> >>> -- 
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> > 
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>
On Friday, May 18, 2012 7:20:06 AM UTC+2, FrankS wrote:
>
> Christophe Grand was "experimenting" with some extensions to if-let and 
> when-let that had implicit ANDs for the let-forms: 
>
>
> https://github.com/cgrand/parsley/blob/master/src/net/cgrand/parsley/util.clj 
>
> It feels intuitive to me to allow multiple if-let-forms like cgrand 
> implements, and I can certainly remember situations where I could have used 
> such a feature. 
>
> -FrankS. 
>
>
>
> On May 16, 2012, at 11:26 AM, dgrnbrg wrote: 
>
> > I too assumed that if/when-let would support multiple bindings, short- 
> > circuiting if one failed, when I started learning Clojure. It seems 
> > that short-circuiting multiple bindings isn't surprising. 
> > 
> > On May 16, 10:56 am, Jay Fields  wrote: 
> >> I've also attempted to use if/when-let with multiple bindings in the 
> past. 
> >> I assumed that it would behave as 'AND' and that no bindings would be 
> >> available in 'else' 
> >> 
> >> Cheers, Jay 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> On Wed, May 16, 2012 at 10:29 AM, Dan Cross  wrote: 
> >>> On Wed, May 16, 2012 at 9:16 AM, Aaron Cohen  
> wrote: 
>  On Wed, May 16, 2012 at 9:10 AM, Walter Tetzner < 
> >>> robot.ninja.saus...@gmail.com> wrote: 
> > To make the bindings work like let, where later bindings can see 
> >>> previous 
> > bindings, I think the most natural way to do it is to have the 
> bindings 
> > behave like the maybe monad. 
> > [...] 
> >> 
>  Saying something is obvious and then using the word monad a paragraph 
> >>> later 
>  is contradictory. ;) 
> >> 
> >>> Hypothetically, "this is obvious, unlike most monads."  Zing! 
> >> 
>  What should happen on the else branch of the if-let; which bindings 
> are 
> >>> in 
>  scope and what would be their values? 
> >> 
> >>> None of the bindings should be in scope. 
> >> 
> >>>- Dan C. 
> >> 
> >>> -- 
> >>> You received this message because you are subscribed to the Google 
> 

Re: docstrings of if-let and when-let incorrect

[Frank Siebenlist]

Christophe Grand was "experimenting" with some extensions to if-let and 
when-let that had implicit ANDs for the let-forms:

https://github.com/cgrand/parsley/blob/master/src/net/cgrand/parsley/util.clj

It feels intuitive to me to allow multiple if-let-forms like cgrand implements, 
and I can certainly remember situations where I could have used such a feature.

-FrankS.



On May 16, 2012, at 11:26 AM, dgrnbrg wrote:

> I too assumed that if/when-let would support multiple bindings, short-
> circuiting if one failed, when I started learning Clojure. It seems
> that short-circuiting multiple bindings isn't surprising.
> 
> On May 16, 10:56 am, Jay Fields  wrote:
>> I've also attempted to use if/when-let with multiple bindings in the past.
>> I assumed that it would behave as 'AND' and that no bindings would be
>> available in 'else'
>> 
>> Cheers, Jay
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> On Wed, May 16, 2012 at 10:29 AM, Dan Cross  wrote:
>>> On Wed, May 16, 2012 at 9:16 AM, Aaron Cohen  wrote:
 On Wed, May 16, 2012 at 9:10 AM, Walter Tetzner <
>>> robot.ninja.saus...@gmail.com> wrote:
> To make the bindings work like let, where later bindings can see
>>> previous
> bindings, I think the most natural way to do it is to have the bindings
> behave like the maybe monad.
> [...]
>> 
 Saying something is obvious and then using the word monad a paragraph
>>> later
 is contradictory. ;)
>> 
>>> Hypothetically, "this is obvious, unlike most monads."  Zing!
>> 
 What should happen on the else branch of the if-let; which bindings are
>>> in
 scope and what would be their values?
>> 
>>> None of the bindings should be in scope.
>> 
>>>- Dan C.
>> 
>>> --
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Re: docstrings of if-let and when-let incorrect

[dgrnbrg]

I too assumed that if/when-let would support multiple bindings, short-
circuiting if one failed, when I started learning Clojure. It seems
that short-circuiting multiple bindings isn't surprising.

On May 16, 10:56 am, Jay Fields  wrote:
> I've also attempted to use if/when-let with multiple bindings in the past.
> I assumed that it would behave as 'AND' and that no bindings would be
> available in 'else'
>
> Cheers, Jay
>
>
>
>
>
>
>
> On Wed, May 16, 2012 at 10:29 AM, Dan Cross  wrote:
> > On Wed, May 16, 2012 at 9:16 AM, Aaron Cohen  wrote:
> > > On Wed, May 16, 2012 at 9:10 AM, Walter Tetzner <
> > robot.ninja.saus...@gmail.com> wrote:
> > >> To make the bindings work like let, where later bindings can see
> > previous
> > >> bindings, I think the most natural way to do it is to have the bindings
> > >> behave like the maybe monad.
> > >> [...]
>
> > > Saying something is obvious and then using the word monad a paragraph
> > later
> > > is contradictory. ;)
>
> > Hypothetically, "this is obvious, unlike most monads."  Zing!
>
> > > What should happen on the else branch of the if-let; which bindings are
> > in
> > > scope and what would be their values?
>
> > None of the bindings should be in scope.
>
> >        - Dan C.
>
> > --
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Re: docstrings of if-let and when-let incorrect

[Jay Fields]

I've also attempted to use if/when-let with multiple bindings in the past.
I assumed that it would behave as 'AND' and that no bindings would be
available in 'else'

Cheers, Jay

On Wed, May 16, 2012 at 10:29 AM, Dan Cross  wrote:

> On Wed, May 16, 2012 at 9:16 AM, Aaron Cohen  wrote:
> > On Wed, May 16, 2012 at 9:10 AM, Walter Tetzner <
> robot.ninja.saus...@gmail.com> wrote:
> >> To make the bindings work like let, where later bindings can see
> previous
> >> bindings, I think the most natural way to do it is to have the bindings
> >> behave like the maybe monad.
> >> [...]
> >
> > Saying something is obvious and then using the word monad a paragraph
> later
> > is contradictory. ;)
>
> Hypothetically, "this is obvious, unlike most monads."  Zing!
>
> > What should happen on the else branch of the if-let; which bindings are
> in
> > scope and what would be their values?
>
> None of the bindings should be in scope.
>
>- Dan C.
>
> --
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Re: docstrings of if-let and when-let incorrect

[Dan Cross]

On Wed, May 16, 2012 at 9:16 AM, Aaron Cohen  wrote:
> On Wed, May 16, 2012 at 9:10 AM, Walter Tetzner 
>  wrote:
>> To make the bindings work like let, where later bindings can see previous
>> bindings, I think the most natural way to do it is to have the bindings
>> behave like the maybe monad.
>> [...]
>
> Saying something is obvious and then using the word monad a paragraph later
> is contradictory. ;)

Hypothetically, "this is obvious, unlike most monads."  Zing!

> What should happen on the else branch of the if-let; which bindings are in
> scope and what would be their values?

None of the bindings should be in scope.

- Dan C.

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Re: docstrings of if-let and when-let incorrect

[Walter Tetzner]

On Wednesday, May 16, 2012 9:16:29 AM UTC-4, Aaron Cohen wrote:
>
> Saying something is obvious and then using the word monad a paragraph 
> later is contradictory. ;)
>
> What should happen on the else branch of the if-let; which bindings are in 
> scope and what would be their values?
>
>
None of the bindings should be available in the else branch, since there 
would be no way to know which will succeed before run-time.

-Walter

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Re: docstrings of if-let and when-let incorrect

[Chris Ford]

Personally, I would intuitively assume that none of the bindings from
if-let would be available in the else branch.

On 16 May 2012 14:36, Moritz Ulrich  wrote:

> On Wed, May 16, 2012 at 3:16 PM, Aaron Cohen  wrote:
> > What should happen on the else branch of the if-let; which bindings are
> in
> > scope and what would be their values?
>
> This is kind of tricky. My opinion tends to "all bindings", but then
> it's difficult to handle lazy evaluation like in (or
> (cheap-computation) (long-computation)).
> One solution for this would be evaluating all arguments 'til the first
> fails, then nil-ing the rest. The problem with this is, that it throws
> away values which could be useful.
>
> --
> Moritz Ulrich
>
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Re: docstrings of if-let and when-let incorrect

[Michael Gardner]

On May 16, 2012, at 8:16 AM, Aaron Cohen wrote:

> Saying something is obvious and then using the word monad a paragraph later 
> is contradictory. ;)

If the word "monad" is scary, just pretend he said "it should short-circuit" 
instead. ;)

> What should happen on the else branch of the if-let; which bindings are in 
> scope and what would be their values?

That's an interesting question. For consistency with the current behavior of 
single-binding if-let, the binding whose value was false should be left unbound 
(as well as successive bindings, given short-circuiting); but I could see going 
either way for the bindings that succeeded. I don't think it matters as much 
that this behavior would be non-obvious, though, because I'd predict the common 
case in the else-branch of a multi-binding if-let would be to not care about 
any of the bindings. That's just my guess, though.

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Re: docstrings of if-let and when-let incorrect

[Moritz Ulrich]

On Wed, May 16, 2012 at 3:16 PM, Aaron Cohen  wrote:
> What should happen on the else branch of the if-let; which bindings are in
> scope and what would be their values?

This is kind of tricky. My opinion tends to "all bindings", but then
it's difficult to handle lazy evaluation like in (or
(cheap-computation) (long-computation)).
One solution for this would be evaluating all arguments 'til the first
fails, then nil-ing the rest. The problem with this is, that it throws
away values which could be useful.

-- 
Moritz Ulrich

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Re: docstrings of if-let and when-let incorrect

[Aaron Cohen]

On Wed, May 16, 2012 at 9:10 AM, Walter Tetzner <
robot.ninja.saus...@gmail.com> wrote:

> On Wednesday, May 16, 2012 9:01:49 AM UTC-4, Stuart Sierra wrote:How would
>> multiple bindings for if-let or when-let work? Should every binding be
>> testedd? Should they be and-ed together? Should it short-circuit if the
>> first is false?
>>
>>
>> I don't think there are obvious answers to those questions.
>>
>
> Well, considering everyone on here that's answered that question said
> 'AND', it seems to be obvious.
>
> To make the bindings work like let, where later bindings can see previous
> bindings, I think the most natural way to do it is to have the bindings
> behave like the maybe monad. The first time you encounter a false value, it
> fails. This way, you are using 'AND', but you don't run the risk of a
> NullPointerException in later bindings if a previous one fails.


Saying something is obvious and then using the word monad a paragraph later
is contradictory. ;)

What should happen on the else branch of the if-let; which bindings are in
scope and what would be their values?

--Aaron

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Re: docstrings of if-let and when-let incorrect

[Walter Tetzner]

>
> On Wednesday, May 16, 2012 9:01:49 AM UTC-4, Stuart Sierra wrote:How would 
> multiple bindings for if-let or when-let work? Should every binding be 
> testedd? Should they be and-ed together? Should it short-circuit if the 
> first is false?
>
> I don't think there are obvious answers to those questions.
>

Well, considering everyone on here that's answered that question said 
'AND', it seems to be obvious.

To make the bindings work like let, where later bindings can see previous 
bindings, I think the most natural way to do it is to have the bindings 
behave like the maybe monad. The first time you encounter a false value, it 
fails. This way, you are using 'AND', but you don't run the risk of a 
NullPointerException in later bindings if a previous one fails.

-Walter

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Re: docstrings of if-let and when-let incorrect

[Stuart Sierra]

How would multiple bindings for if-let or when-let work? Should every 
binding be testedd? Should they be and-ed together? Should it short-circuit 
if the first is false?

I don't think there are obvious answers to those questions.
-S

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Re: docstrings of if-let and when-let incorrect

[Vinzent]

>
> As the logical AND of all of the multiple forms?  The OR?  Only use the 
> first expression?  Only the last?
>

It should be AND.

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Re: docstrings of if-let and when-let incorrect

[Dan Cross]

On Tue, May 15, 2012 at 3:47 PM, Walter Tetzner
 wrote:
> On Tuesday, May 15, 2012 3:41:58 PM UTC-4, Dan Cross wrote:
>> My own personal opinion is that it makes sense in combination with 'and',
>> but others may feel differently.  E.g.,
>>
>>     (when-let [a (allocate-thing) b (read-into-thing a) c
>> (extract-something-from-thing b)]
>>       (do-something-with c))
>>
>> makes intuitive sense to me.  If, at any stage of the execution, any of a,
>> b or c was nil, the evaluation would stop and the (when-let) form would
>> return nil.
>
> So judging by both your response and my response, it should behave like the
> maybe monad.

Yes, that's a very good characterization.

- Dan C.

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Re: docstrings of if-let and when-let incorrect

[Michael Gardner]

On May 15, 2012, at 3:15 PM, Andy Fingerhut wrote:

> If if-let/when-let had multiple bindings, how would you propose to define the 
> condition of whether to do the "then" branch?
> 
> As the logical AND of all of the multiple forms?  The OR?  Only use the first 
> expression?  Only the last?
> 
> I don't see that any of those is any more clear or "least surprising" than 
> any of the others.  Permitting only one makes that part of the behavior 
> clear, at least.

AND is the obvious choice, IMO. People will probably still have to look up what 
happens with multiple bindings from time to time, but that doesn't seem worse 
than having to look up whether if-let and when-let even support multiple 
bindings.

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Re: docstrings of if-let and when-let incorrect

[Andy Fingerhut]

If if-let/when-let had multiple bindings, how would you propose to define the 
condition of whether to do the "then" branch?

As the logical AND of all of the multiple forms?  The OR?  Only use the first 
expression?  Only the last?

I don't see that any of those is any more clear or "least surprising" than any 
of the others.  Permitting only one makes that part of the behavior clear, at 
least.

Andy

On May 15, 2012, at 12:09 PM, Hubert Iwaniuk wrote:

> I tried using if-let with multiple binding in past as well.
> Following least surprise principle, I would like to see support for multiple 
> bindings.
> 
> Cheers,
> Hubert.
>>  Vinzent May 15, 2012 5:47 PM
>> Or maybe if-let and when-let should support multiple bindings, like the doc 
>> states.

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Re: docstrings of if-let and when-let incorrect

[Walter Tetzner]

On Tuesday, May 15, 2012 3:41:58 PM UTC-4, Dan Cross wrote:
>
> My own personal opinion is that it makes sense in combination with 'and', 
> but others may feel differently.  E.g.,
>
> (when-let [a (allocate-thing) b (read-into-thing a) c 
> (extract-something-from-thing b)]
>   (do-something-with c))
>
> makes intuitive sense to me.  If, at any stage of the execution, any of a, 
> b or c was nil, the evaluation would stop and the (when-let) form would 
> return nil.
>
>
So judging by both your response and my response, it should behave like the 
maybe monad.

-Walter

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Re: docstrings of if-let and when-let incorrect

[Dan Cross]

On Tue, May 15, 2012 at 3:26 PM, Aaron Cohen  wrote:

> Does the principle of least surprise suggest that multiple bindings be
> combined with AND or OR?


My own personal opinion is that it makes sense in combination with 'and',
but others may feel differently.  E.g.,

(when-let [a (allocate-thing) b (read-into-thing a) c
(extract-something-from-thing b)]
  (do-something-with c))

makes intuitive sense to me.  If, at any stage of the execution, any of a,
b or c was nil, the evaluation would stop and the (when-let) form would
return nil.

- Dan C.

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Re: docstrings of if-let and when-let incorrect

[Walter Tetzner]

On Tuesday, May 15, 2012 3:26:52 PM UTC-4, Aaron Cohen wrote:
>
> Does the principle of least surprise suggest that multiple bindings be 
> combined with AND or OR?
>
>  
For `when-let', I would expect it to work like nested when-lets:

(when-let [x (exp-1)
   y (exp-2 x)
   z (exp-3 y)]
  [x y z])

would be the same as

(when-let [x (exp-1)]
  (when-let [y (exp-2 x)]
(when-let [z (exp-3 y)]
  [x y z])))

For the behavior of `if-let' to not be suprising given this definition
of `when-let', I think it would have to behave similarily:

(if-let [x (exp-1)
 y (exp-2 x)
 z (exp-3 y)]
  [x y z]
  'failed)

would be the same as

(if-let [x (exp-1)]
  (if-let [y (exp-2 x)]
(if-let [z (exp-3 y)]
  [x y z]
  'failed)
'failed)
  'failed)

So, AND I guess. But later expressions can refer to earlier ones, just
like in `let'.

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Re: docstrings of if-let and when-let incorrect

[Aaron Cohen]

Does the principle of least surprise suggest that multiple bindings be
combined with AND or OR?

--Aaron

On Tue, May 15, 2012 at 3:09 PM, Hubert Iwaniuk  wrote:

> I tried using if-let with multiple binding in past as well.
> Following least surprise principle, I would like to see support for
> multiple bindings.
>
> Cheers,
> Hubert.
>
>   Vinzent 
>  May 15, 2012 5:47 PM
> Or maybe if-let and when-let should support multiple bindings, like the
> doc states.
>
> воскресенье, 13 мая 2012 г., 4:55:40 UTC+6 пользователь Borkdude написал:
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>   Borkdude 
>  May 13, 2012 12:55 AM
> The docstring of if-let is as follows:
>
> bindings => binding-form test
>
> If test is true, evaluates then with binding-form bound to the value of
> test, if not, yields else
>
> I think it should be mentioned in the docs that if-let and when-let
> support only *one binding*, not multiple bindings (like for example
> https://www.refheap.com/paste/2700).
>
> Kind regards,
>
> Michiel
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Re: docstrings of if-let and when-let incorrect

[Evan Gamble]

If if-let and when-let don't get support for multiple bindings, you could 
try https://github.com/egamble/let-else .

On Tuesday, May 15, 2012 12:09:08 PM UTC-7, Hubert Iwaniuk wrote:
>
> I tried using if-let with multiple binding in past as well.
> Following least surprise principle, I would like to see support for 
> multiple bindings.
>
> Cheers,
> Hubert
>  

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Re: docstrings of if-let and when-let incorrect

[Hubert Iwaniuk]

I tried using if-let with multiple binding in past as well.
Following least surprise principle, I would like to see support for 
multiple bindings.


Cheers,
Hubert.

Vinzent 
May 15, 2012 5:47 PM
Or maybe if-let and when-let should support multiple bindings, like 
the doc states.


воскресенье, 13 мая 2012 г., 4:55:40 UTC+6 пользователь Borkdude 
написал: --

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Borkdude 
May 13, 2012 12:55 AM
The docstring of if-let is as follows:

bindings => binding-form test

If test is true, evaluates then with binding-form bound to the value of
test, if not, yields else

I think it should be mentioned in the docs that if-let and when-let 
support only /one binding/, not multiple bindings (like for 
example https://www.refheap.com/paste/2700).


Kind regards,

Michiel
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Re: docstrings of if-let and when-let incorrect

[Vinzent]

Or maybe if-let and when-let should support multiple bindings, like the doc 
states.

воскресенье, 13 мая 2012 г., 4:55:40 UTC+6 пользователь Borkdude написал:
>
> The docstring of if-let is as follows:
>
> bindings => binding-form test
>
> If test is true, evaluates then with binding-form bound to the value of 
> test, if not, yields else
>
> I think it should be mentioned in the docs that if-let and when-let 
> support only *one binding*, not multiple bindings (like for example 
> https://www.refheap.com/paste/2700).
>  
> Kind regards,
>
> Michiel
>

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Re: docstrings of if-let and when-let incorrect

[Stuart Sierra]

Reasonable enough. Patch welcome.
-S

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docstrings of if-let and when-let incorrect

[Borkdude]

The docstring of if-let is as follows:

bindings => binding-form test

If test is true, evaluates then with binding-form bound to the value of 
test, if not, yields else

I think it should be mentioned in the docs that if-let and when-let support 
only *one binding*, not multiple bindings (like for 
example https://www.refheap.com/paste/2700).
 
Kind regards,

Michiel

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