crystal-lang/crystal

The Crystal programming language | http://crystal-lang.org | Fund Crystal's development: http://is.gd/X7PRtI | Docs: http://crystal-lang.org/docs/ | API: http://crystal-lang.org/api/

George Dietrich

@Blacksmoke16

You can append them to a constant, then iterate over it in a finished hook

But im not really sure you need a macro here, versus just a method and hash of procs

Lance Dillon

@riffraff169

yeah, just create a dispatch table....hash key being name, value being proc, then call the proc when a key matches

could even have it be a list of procs, that can be called in order... and can change them dynamically if needed... basically like hooks

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@FromIRC

<Guest64> i was thinking something similar as well. i may be able to make a hash of string, proc() work to my liking

<Guest64> thanks for the ideas

Kirk Haines

@wyhaines

@guest64 Macros create code in the place where the macro is called. Also, macros can not call other macros -- they look like methods, but they aren't really methods. However, macros do have access to constants. So you could have your first macro, the one that defines a proc, inject data into a constant that a later macro, involved with the case statement creation, accesses to build said case statement.

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@FromIRC

<Guest64> thanks for the advice, im trying to use a hash to contain my map of String, Proc, but while trying to add my procs to the hash I get this error:

<Guest64> ProcMap = Hash(String, Proc).new

<Guest64> Error: can't use Proc(T, R) as generic type argument yet, use a more specific type

George Dietrich

@Blacksmoke16

you need to type your proc

Proc(String, Int32) e.g. if it accepts a string an returns an int32

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@FromIRC

<Guest64> each proc has diufferent types, how can i make that work with the hash

<Guest64> IE each proc added to the hash do not share the same definition

George Dietrich

@Blacksmoke16

that's going to be painful

what are these procs used for?

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@FromIRC

<Guest64> thats hard to explain without going into depth of the project. the procs are basically synonyms of existing libc functions which their pointer address is returned back to the dynamic linker during the binding stage to determine which function symbol points to which function

George Dietrich

@Blacksmoke16

might be able to wrap these procs in structs

somethign like

abstract struct Callable
end

struct Proc1 < Callable
  def call # define args/return type
  end
end

struct Proc2 < Callable
  def call # define args/return type
  end
end

hash = Hash(String, Callable).new

the gist of it is that you cant have a hash with type of Proc, would need to specify the types of procs that can be in the hash

i suppose technically the macro approach you wanted to take would work around this by defining a hash literal, which would essentially type itself

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@FromIRC

<Guest64> hmm, wrapping the procs inside a struct might work. i never thought of that

<Guest64> could you expand more on this hash literal you speak of?

George Dietrich

@Blacksmoke16

https://play.crystal-lang.org/#/r/biyi

the type of literal hashes are inferred based on the values in the literal

but hashes with a lot of unioned types is kinda meh

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@FromIRC

<Guest64> yea thats probably going to be messy since these procs vary in arguments from 0 to 6 with various types ranging from simply ints up to pointers to structs

<Guest64> although thats neat that works like that. ill keep that in mind

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@FromIRC

<Guest64> @Blacksmoke16: I am having a bit of trouble implementing a simple test for your callable suggest: https://play.crystal-lang.org/#/r/biyo im probably not doing this right at all heh

George Dietrich

@Blacksmoke16

https://play.crystal-lang.org/#/r/biyq

prob not going to be that easy when you add more, as the compiler wont be able to guarantee that the value returned from the hash has that method with those arguments

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@FromIRC

<Guest64> hmm yes, i will have to ponder about that. thanks for the assistance

George Dietrich

@Blacksmoke16

are the string keys anything significant?

Kirk Haines

@wyhaines

Yeah, it won't work once you add a second struct.

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@FromIRC

<Guest64> the string keys are just a way to fetch the correct proc pointer from the hash to return to the dynamic linker. the dynamic linker actually gives me a char*, but i convert it to a string for use.

Kirk Haines

@wyhaines

I've been down this road when I built my #send implementation. :)

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@FromIRC

<Guest64> if it matters im attempting to implement rtld-audit for fun and experience: https://man7.org/linux/man-pages/man7/rtld-audit.7.html

George Dietrich

@Blacksmoke16

https://play.crystal-lang.org/#/r/biyx

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@FromIRC

<Guest64> i have everything working, im just testing new theories and ways to generate code

George Dietrich

@Blacksmoke16

if the strings are just a way to know what the proc is, you can make the proc's class the key of the hash

could also ofc have a #get method that returns the related Callable instance that you could then directly invoke #call on

but i just combined them into 1 method

Kirk Haines

@wyhaines

Yeah. You can't get away from storing the class/type of Proc or Struct somewhere, in some form.

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@FromIRC

<Guest64> random question: is there a way for crystal to expand macros in other files, then move the expanded code into another file for use? if that makes any sense.

<Guest64> for example: https://pastebin.com/rez9g1t2 vs https://pastebin.com/sAfrAy4M

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@FromIRC

<Guest64> i wish there was better docs for macros somewhere. it seems to have all these cool features but i cant make heads or tails of them

George Dietrich

@Blacksmoke16

you already asked this and we answered it twice :P

:point_up: July 11, 2021 1:45 AM

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@FromIRC

<Guest64> ha, i suppose i did, my bad

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