On Wed, Jul 18, 2018, 2:40 PM Gregg Reynolds <d...@mobileink.com> wrote:
>
>
> On Wed, Jul 18, 2018, 2:25 PM Robert Levy <r.p.l...@gmail.com> wrote:
>
>> > Of course you have to "evaluate" to know that, but you also have to
>> evaluate "2" in the same way to know what it means.
>>
>> I think you're missing the point.
>>
>
> I think maybe we're talking about different things.
>
> 2 is literal because you read it, eval it, print it, and 2 (the result of
>> evaluation) as printed is the same as the original input. A function is
>> read, eval'd, printed and is *not* the same as what was read in. E.g {:a
>> +} => {:a #function[clojure.core/+]}
>>
>
> Same meaning?
>
I.e. alpha conversion. Just a rewrite, not an eval?
>
>> Literals can be persisted to strings and read back in with no problem,
>> whereas non-literals can't.
>>
>
> That's a different definition of "literal", no? James talked about
> evaluation, not printed form. Value != Print representation?
>
>>
>> On Wed, Jul 18, 2018 at 12:19 PM Gregg Reynolds <d...@mobileink.com>
>> wrote:
>>
>>>
>>>
>>> On Wed, Jul 18, 2018, 1:55 PM James Reeves <ja...@booleanknot.com>
>>> wrote:
>>>
>>>> On Wed, 18 Jul 2018 at 19:38, Gregg Reynolds <d...@mobileink.com> wrote:
>>>>
>>>>>
>>>>> On Tue, Jul 17, 2018, 4:11 PM James Reeves <ja...@booleanknot.com>
>>>>> wrote:
>>>>>
>>>>>>
>>>>>> A data literal evaluates to itself. So for example, `2` is a
>>>>>> literal, because we only need to read it to know its value, whereas `(+
>>>>>> 1 1)` isn't a literal, because we also need to evaluate it to work
>>>>>> out the value.
>>>>>>
>>>>>
>>>>> Fair enough. But by that definition function expressions are also
>>>>> literals.
>>>>>
>>>>
>>>> Not at all:
>>>>
>>>> user=> (defn literal? [s] (let [e (read-string s)] (= e (eval e))))
>>>> #'user/literal?
>>>> user=> (literal? "2")
>>>> true
>>>> user=> (literal? "(fn [x] x)")
>>>> false
>>>> user=> (literal? "#(%)")
>>>> false
>>>> user=> (literal? "+")
>>>> false
>>>>
>>>> Function expressions don't evaluate to themselves.
>>>>
>>>
>>> To me that means either the definition is wrong or your literal? is
>>> rigged. Probably the latter; "literal" is meta, it can't be in the language.
>>>
>>> Look at it this way: the meaning ("value") of "lambda x.x+1" is just the
>>> function that increments its arg. Of course you have to "evaluate" to know
>>> that, but you also have to evaluate "2" in the same way to know what it
>>> means. Meaning "reduce", and neither form can be further reduced.
>>>
>>> Anyway my point is that clojure, like lisp, is a form of the lambda
>>> calculus, where everything is a function, even the Nats like 2. To me at
>>> least that is one of the most important lessons of functional programming.
>>> Ymmv.
>>>
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