Is there any way (or could there be any way, in the future) of getting the code from lambda expressions as a string?

I've noticed that if I have an error with a lambda that looks like, say
  x=>x+a

the error message will come up referring to it as
  (x) => x + a

so some level of processing has already been done on the expression. Can I get at any of it during compilation? It would be useful for automatic program rewriting.

On Tuesday, 31 March 2015 at 12:49:36 UTC, Vlad Levenfeld wrote:
> Is there any way (or could there be any way, in the future) of getting the code from lambda expressions as a string?
>
> I've noticed that if I have an error with a lambda that looks like, say
>   x=>x+a
>
> the error message will come up referring to it as
>   (x) => x + a
>
> so some level of processing has already been done on the expression. Can I get at any of it during compilation? It would be useful for automatic program rewriting.

Short answer: no. .codeof for functions is something I've wanted for ages, but no movement so far.

On Tuesday, 31 March 2015 at 13:25:47 UTC, John Colvin wrote:
> On Tuesday, 31 March 2015 at 12:49:36 UTC, Vlad Levenfeld wrote:
>> Is there any way (or could there be any way, in the future) of getting the code from lambda expressions as a string?
>>
>> I've noticed that if I have an error with a lambda that looks like, say
>>  x=>x+a
>>
>> the error message will come up referring to it as
>>  (x) => x + a
>>
>> so some level of processing has already been done on the expression. Can I get at any of it during compilation? It would be useful for automatic program rewriting.
>
> Short answer: no. .codeof for functions is something I've wanted for ages, but no movement so far.

:(

On Tue, 31 Mar 2015 13:25:46 +0000, John Colvin wrote:

> Short answer: no. .codeof for functions is something I've wanted for ages, but no movement so far.

'cause `.codeof` is a can of worms. it is just a bad replace for AST macros, and having it means that internal string representation should be maintained intact for very long time.

that's if i got you right and you mean that `.codeof` should return something like javascript's, `.toString` on functions: rebuild string representation of function source code.

besides, it is impossible to write `.codeof` for functions without source. ;-)

On Wednesday, 1 April 2015 at 23:29:00 UTC, Vlad Levenfeld wrote:
> On Tuesday, 31 March 2015 at 13:25:47 UTC, John Colvin wrote:
>> On Tuesday, 31 March 2015 at 12:49:36 UTC, Vlad Levenfeld wrote:
>>> Is there any way (or could there be any way, in the future) of getting the code from lambda expressions as a string?
>>>
>>> I've noticed that if I have an error with a lambda that looks like, say
>>> x=>x+a
>>>
>>> the error message will come up referring to it as
>>> (x) => x + a
>>>
>>> so some level of processing has already been done on the expression. Can I get at any of it during compilation? It would be useful for automatic program rewriting.
>>
>> Short answer: no. .codeof for functions is something I've wanted for ages, but no movement so far.
>
> :(

On a more positive note, there's probably an OK way of achieving
your particular goal without this. Do you have an example?

On Thursday, 2 April 2015 at 19:27:21 UTC, John Colvin wrote:
> On Wednesday, 1 April 2015 at 23:29:00 UTC, Vlad Levenfeld wrote:
>> On Tuesday, 31 March 2015 at 13:25:47 UTC, John Colvin wrote:
>>> On Tuesday, 31 March 2015 at 12:49:36 UTC, Vlad Levenfeld wrote:
>>>> Is there any way (or could there be any way, in the future) of getting the code from lambda expressions as a string?
>>>>
>>>> I've noticed that if I have an error with a lambda that looks like, say
>>>> x=>x+a
>>>>
>>>> the error message will come up referring to it as
>>>> (x) => x + a
>>>>
>>>> so some level of processing has already been done on the expression. Can I get at any of it during compilation? It would be useful for automatic program rewriting.
>>>
>>> Short answer: no. .codeof for functions is something I've wanted for ages, but no movement so far.
>>
>> :(
>
> On a more positive note, there's probably an OK way of achieving
> your particular goal without this. Do you have an example?

Well I was just thinking of turning

  r[].map!(v => v.xy*2).zip (s[]).map!((v,t) => vec2(v.x*cos(t), v.y*sin(t))).to_vertex_shader ();

  or something like that, into a shader program.

Right now I have to do it with strings:

  r[].vertex_shader!(`v`, q{
    vec2 u = v.xy*2;
    gl_Position = vec2(v.x*cos(t), v.y*sin(t));
  });

I just keep thinking that, if I have programs composed of individual processing stages, like

  auto aspect_ratio_correction (T,U)(T computation, U canvas) {
    return
      zip (computation, repeat (canvas.aspect_ratio, computation.length))
        .map!((v, a_r) => v/a_r);
  }

then it's so that I can put them in UFCS chains, so

  vec2[] vertices;
  float time;
  Display display;

  auto kernel = some_program (vertices[], time)
    .aspect_ratio_correction (display);

is able to be run on the cpu or gpu and this decision must be made lazily:

  kernel[].array; // cpu
  kernel[].computed_on_gpu.array; // compute on gpu, read back to cpu

So I'd like to turn "place of execution" into a lazily evaluated range adaptor, and maybe reduce the need to keep different cpu/gpu code for the same algorithms. This seems impossible without something like .codeof or, better yet, ASTs.

I can already unwrap the type of a composed range to get at how its constructed, but I don't get any information on the functions that are involved with higher-order function adaptors. The idea of doing compile-time restructuring of these ufcs chains is interesting to me, but I feel like I only have half of what I need to give it a proper try.