Re: trait to get the body code of a function?
So, does anyone want to take up the challenge of writing such a function that can safely get the function body? I guess D CTFE'able D parser would be required and basically use what I've given above. I've seen a few lexers around but not messed with them. This will at least fill in a gap.
Re: trait to get the body code of a function?
On Thursday, 26 July 2018 at 13:27:09 UTC, Alex wrote:
On Thursday, 26 July 2018 at 11:54:39 UTC, Mr.Bingo wrote:
The string itself could be useful however... Whatever OP has
in mind with this string...
Having a code block is useful in many ways simply because not
having it is the most limiting case. If one doesn't have it
and requires it then it is impossible for them to do what they
want. If one does have it and has no need, then no loss. Lots
of people like to err on the side of "caution" which is really
the side of limitations and frustrations and laziness. Of
course, sometimes things should be limited, but I think this
is probably not one of those cases(I see no harm in allowing
meta code to get a function body and, say, create another
function based off it but a slight change.
For example, one could mutate algorithms and run genetics
algorithms on them to see how function scan evolve. This might
lead to genetic ways to assemble programs. In any case, one
can't do it since one can't get at a functions body.
For example, maybe one wants a way to debug a mixin:
mixin("int x;"); <- can't debug
void foo()
{
int x;
}
mixin(funcBody!foo) <- can debug since we defined foo outside
of the mixin and the compiler see's it naturally.
I'm with you in this part.
I would argue, just because of "type safety" you mentioned, D
should not allow one to get the function body. The type
safety is not achievable because of
https://en.wikipedia.org/wiki/Lambda_calculus#Undecidability_of_equivalence
What the hell does that have to do with anything? I don't know
what you are talking about when it comes to "type safety" and
equivalence. What I am talking about is being able to parse
the function body in a type safe way rather than having to
hack strings or write a D parser oneself.
Instead of
"int x;"
one has >
or whatever the parser parses in to(some type of AST).
I'll try to reformulate this.
Take the example given at
https://dlang.org/spec/function.html#closures
Paragraph 2.
Now, examine the contents of functions abc and def.
Does the functionality differ? For sure not.
Does the compiler knows it? It is not guaranteed.
The article I cited and the literature behind it state, that in
general, an equivalence of function contents can not be
tracked. However, to state for a function to be equal with
another function exactly this is needed. And I thought you
meant this by "type safety"...
But this doesn't matter... If the idea is to return a string then
it doesn't matter, just return the requested function body. If is
to return an AST then it just gives(in whatever suitable form)
the AST for the requested function...
It's really not complicated:
Suppose one could get the function body as a string and suppose
one had a D parser. Just use the D parser on the string and
return the AST. D already has the D parser in it and also already
has the string in it. It's just a matter of someone exposing that
to the programmer to use. There is no issue anywhere because the
function cannot change while compiling(hence there can be no sync
issues).
I mean, if we want to see the function body we can just open up a
text editor... If we want to know the syntactical structure we
just parse the code with our brain. All that is being asked is to
have the compiler give us the string(easy) and parse it for us in
to some easy to use structure(some work but not hard, in fact, it
might be easy).
There are no function pointers to deal with, no compiling, etc.
Again, we can already do this stuff by hand by using import to
import the file containing the function we want to get... and use
a D parser to find the function proper and then grab the function
body and return it as a string. It is not hard to do but does
require using -J on the source path.
Here is a simple dumb way to get the function body. The problem
with "library" solutions is that they are not robust.
import std.stdio;
int foo(int x)
{
return x;
}
auto GetFunctionBody(alias B)()
{
import std.traits, std.meta, std.typecons, std.algorithm,
std.string, std.range;
enum ft = typeof(B).stringof;
enum rt = ReturnType!(B).stringof;
enum fn = fullyQualifiedName!(B);
enum n = split(fn, ".")[$-1];
enum mn = join(split(fn, ".")[0..$-1])~".d";
enum fs = rt~" "~n~ft[rt.length..$];
enum file = import(mn);
pragma(msg, n, ", ", ft, ", ", rt, ", ", fn, ", ", mn, ", ", fs);
auto res = "";
auto found = false;
for(int i = 0; i < file.length - fs.length; i++)
{
if (file[i..i+fs.length] == fs)
found = true;
if (found)
res ~= file[i];
if (file[i] == '}')
found = false;
}
return res;
}
int main()
{
writeln(GetFunctionB
Re: trait to get the body code of a function?
On Wednesday, 25 July 2018 at 19:10:03 UTC, 12345swordy wrote: On Wednesday, 25 July 2018 at 19:05:08 UTC, Guillaume Lathoud wrote: On Wednesday, 25 July 2018 at 04:46:20 UTC, rikki cattermole wrote: On 25/07/2018 5:32 AM, Guillaume Lathoud wrote: Thanks for all the answers. I've just had a look at an alternative: using dmd as a package. However that's a lot of doc to browse... Maybe someone has experience with dmd as a package? Not a solution. Leaks memory, not reusable and in general not very friendly to work with. Thanks. Please submit a bug report to Bugzilla on this, as I am also interest in this. Alexander I once had a similar PR in DMD to a potential `__traits(getFunctionBody, X)` for `__traits(documentation, X)`: https://github.com/dlang/dmd/pull/6872 There was a bit of a forum discussion about it: https://forum.dlang.org/post/cwjtsmnepvgvl...@forum.dlang.org The gist: Putting this in the Phantom Zone due it needing a compelling use case(s) to justify consuming memory and compilation time. << tl;dr: just Bugzilla won't do it. It will need a short DIP illustrating use cases. Sorry. Happy to implement it for you though.
Re: trait to get the body code of a function?
On Thursday, 26 July 2018 at 11:54:39 UTC, Mr.Bingo wrote:
The string itself could be useful however... Whatever OP has
in mind with this string...
Having a code block is useful in many ways simply because not
having it is the most limiting case. If one doesn't have it and
requires it then it is impossible for them to do what they
want. If one does have it and has no need, then no loss. Lots
of people like to err on the side of "caution" which is really
the side of limitations and frustrations and laziness. Of
course, sometimes things should be limited, but I think this is
probably not one of those cases(I see no harm in allowing meta
code to get a function body and, say, create another function
based off it but a slight change.
For example, one could mutate algorithms and run genetics
algorithms on them to see how function scan evolve. This might
lead to genetic ways to assemble programs. In any case, one
can't do it since one can't get at a functions body.
For example, maybe one wants a way to debug a mixin:
mixin("int x;"); <- can't debug
void foo()
{
int x;
}
mixin(funcBody!foo) <- can debug since we defined foo outside
of the mixin and the compiler see's it naturally.
I'm with you in this part.
I would argue, just because of "type safety" you mentioned, D
should not allow one to get the function body. The type safety
is not achievable because of
https://en.wikipedia.org/wiki/Lambda_calculus#Undecidability_of_equivalence
What the hell does that have to do with anything? I don't know
what you are talking about when it comes to "type safety" and
equivalence. What I am talking about is being able to parse the
function body in a type safe way rather than having to hack
strings or write a D parser oneself.
Instead of
"int x;"
one has >
or whatever the parser parses in to(some type of AST).
I'll try to reformulate this.
Take the example given at
https://dlang.org/spec/function.html#closures
Paragraph 2.
Now, examine the contents of functions abc and def.
Does the functionality differ? For sure not.
Does the compiler knows it? It is not guaranteed.
The article I cited and the literature behind it state, that in
general, an equivalence of function contents can not be tracked.
However, to state for a function to be equal with another
function exactly this is needed. And I thought you meant this by
"type safety"...
Re: trait to get the body code of a function?
On Thursday, 26 July 2018 at 10:20:04 UTC, Alex wrote:
On Thursday, 26 July 2018 at 07:32:19 UTC, Mr.Bingo wrote:
If all you need is the string you can write a template
function that imports the file and searches for the function
and returns it's body.
It's not very robust but it can work for some cases. D really
should allow one to get the function body in D, possibly in a
type safe way(such as each line is parsed properly and return
type info about what the line contains.
I would argue, just because of "type safety" you mentioned, D
should not allow one to get the function body. The type safety
is not achievable because of
https://en.wikipedia.org/wiki/Lambda_calculus#Undecidability_of_equivalence
What the hell does that have to do with anything? I don't know
what you are talking about when it comes to "type safety" and
equivalence. What I am talking about is being able to parse the
function body in a type safe way rather than having to hack
strings or write a D parser oneself.
Instead of
"int x;"
one has >
or whatever the parser parses in to(some type of AST).
The string itself could be useful however... Whatever OP has in
mind with this string...
Having a code block is useful in many ways simply because not
having it is the most limiting case. If one doesn't have it and
requires it then it is impossible for them to do what they want.
If one does have it and has no need, then no loss. Lots of people
like to err on the side of "caution" which is really the side of
limitations and frustrations and laziness. Of course, sometimes
things should be limited, but I think this is probably not one of
those cases(I see no harm in allowing meta code to get a function
body and, say, create another function based off it but a slight
change.
For example, one could mutate algorithms and run genetics
algorithms on them to see how function scan evolve. This might
lead to genetic ways to assemble programs. In any case, one can't
do it since one can't get at a functions body.
For example, maybe one wants a way to debug a mixin:
mixin("int x;"); <- can't debug
void foo()
{
int x;
}
mixin(funcBody!foo) <- can debug since we defined foo outside of
the mixin and the compiler see's it naturally.
Re: trait to get the body code of a function?
On Thursday, 26 July 2018 at 07:32:19 UTC, Mr.Bingo wrote: If all you need is the string you can write a template function that imports the file and searches for the function and returns it's body. It's not very robust but it can work for some cases. D really should allow one to get the function body in D, possibly in a type safe way(such as each line is parsed properly and return type info about what the line contains. I would argue, just because of "type safety" you mentioned, D should not allow one to get the function body. The type safety is not achievable because of https://en.wikipedia.org/wiki/Lambda_calculus#Undecidability_of_equivalence The string itself could be useful however... Whatever OP has in mind with this string...
Re: trait to get the body code of a function?
On Tuesday, 24 July 2018 at 04:43:33 UTC, Guillaume Lathoud wrote: Hello, __traits and std.traits already offer access to function information like input parameters, e.g. in std.traits: ParameterIdentifierTuple ParameterStorageClassTuple Even if that might sound strange, is there a compile time access to the body of the function, e.g. as a code string, or at least to the filename where it was declared? I have not found a direct "string" access, but I found these: https://dlang.org/phobos/std_traits.html#moduleName https://dlang.org/phobos/std_traits.html#packageName ...and I am not sure how to proceed from here to get the code as a string that declared the function. Context: I have some compile-time ideas in mind (code transformation). Best regards, Guillaume Lathoud If all you need is the string you can write a template function that imports the file and searches for the function and returns it's body. It's not very robust but it can work for some cases. D really should allow one to get the function body in D, possibly in a type safe way(such as each line is parsed properly and return type info about what the line contains.
Re: trait to get the body code of a function?
On Wednesday, 25 July 2018 at 19:05:08 UTC, Guillaume Lathoud wrote: On Wednesday, 25 July 2018 at 04:46:20 UTC, rikki cattermole wrote: On 25/07/2018 5:32 AM, Guillaume Lathoud wrote: Thanks for all the answers. I've just had a look at an alternative: using dmd as a package. However that's a lot of doc to browse... Maybe someone has experience with dmd as a package? Not a solution. Leaks memory, not reusable and in general not very friendly to work with. Thanks. Please submit a bug report to Bugzilla on this, as I am also interest in this. Alexander
Re: trait to get the body code of a function?
On Wednesday, 25 July 2018 at 04:46:20 UTC, rikki cattermole wrote: On 25/07/2018 5:32 AM, Guillaume Lathoud wrote: Thanks for all the answers. I've just had a look at an alternative: using dmd as a package. However that's a lot of doc to browse... Maybe someone has experience with dmd as a package? Not a solution. Leaks memory, not reusable and in general not very friendly to work with. Thanks.
Re: trait to get the body code of a function?
On 25/07/2018 5:32 AM, Guillaume Lathoud wrote: Thanks for all the answers. I've just had a look at an alternative: using dmd as a package. However that's a lot of doc to browse... Maybe someone has experience with dmd as a package? Not a solution. Leaks memory, not reusable and in general not very friendly to work with.
Re: trait to get the body code of a function?
On Tuesday, 24 July 2018 at 14:26:45 UTC, 12345swordy wrote: On Tuesday, 24 July 2018 at 05:27:36 UTC, rikki cattermole wrote: On 24/07/2018 4:43 PM, Guillaume Lathoud wrote: [...] Doesn't exist. Well, IMO it should exist as it can be quite useful for generating metainfo. Thanks for all the answers. I've just had a look at an alternative: using dmd as a package. However that's a lot of doc to browse... Maybe someone has experience with dmd as a package? Otherwise I'll just stick to strings, but it'd be nice to have. Best regards, Guillaume
Re: trait to get the body code of a function?
On Tuesday, 24 July 2018 at 05:27:36 UTC, rikki cattermole wrote: On 24/07/2018 4:43 PM, Guillaume Lathoud wrote: [...] Doesn't exist. Well, IMO it should exist as it can be quite useful for generating metainfo.
Re: trait to get the body code of a function?
On Tuesday, 24 July 2018 at 04:43:33 UTC, Guillaume Lathoud wrote: Hello, __traits and std.traits already offer access to function information like input parameters, e.g. in std.traits: ParameterIdentifierTuple ParameterStorageClassTuple Even if that might sound strange, is there a compile time access to the body of the function, e.g. as a code string, or at least to the filename where it was declared? I have not found a direct "string" access, but I found these: https://dlang.org/phobos/std_traits.html#moduleName https://dlang.org/phobos/std_traits.html#packageName ...and I am not sure how to proceed from here to get the code as a string that declared the function. Context: I have some compile-time ideas in mind (code transformation). Best regards, Guillaume Lathoud Not sure if this could be of interest: https://forum.dlang.org/thread/ifllo2$a45$1...@digitalmars.com
Re: trait to get the body code of a function?
On 24/07/2018 4:43 PM, Guillaume Lathoud wrote: Hello, __traits and std.traits already offer access to function information like input parameters, e.g. in std.traits: ParameterIdentifierTuple ParameterStorageClassTuple Even if that might sound strange, is there a compile time access to the body of the function, e.g. as a code string, or at least to the filename where it was declared? I have not found a direct "string" access, but I found these: https://dlang.org/phobos/std_traits.html#moduleName https://dlang.org/phobos/std_traits.html#packageName ...and I am not sure how to proceed from here to get the code as a string that declared the function. Context: I have some compile-time ideas in mind (code transformation). Best regards, Guillaume Lathoud Doesn't exist.
trait to get the body code of a function?
Hello, __traits and std.traits already offer access to function information like input parameters, e.g. in std.traits: ParameterIdentifierTuple ParameterStorageClassTuple Even if that might sound strange, is there a compile time access to the body of the function, e.g. as a code string, or at least to the filename where it was declared? I have not found a direct "string" access, but I found these: https://dlang.org/phobos/std_traits.html#moduleName https://dlang.org/phobos/std_traits.html#packageName ...and I am not sure how to proceed from here to get the code as a string that declared the function. Context: I have some compile-time ideas in mind (code transformation). Best regards, Guillaume Lathoud
