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/

Benjamin Wade

@RespiteSage

In particular I'm thinking about the case of a + b, where b is a wider type than a.

So like Int8#+(UInt64), as an extreme example.

Daniel Worrall

@Daniel-Worrall

Int#+(otherInt) returns self class, so no

Benjamin Wade

@RespiteSage

No, that's not what I mean.

Daniel Worrall

@Daniel-Worrall

It'll raise overflow, not promote

Benjamin Wade

@RespiteSage

This is what I mean: https://carc.in/#/r/bid3

Maybe "type promotion" was the wrong wording.

Unless I'm sorely mistaken, the hardware doesn't do arithmetic on numbers of mismatched length, so either Crystal or LLVM has to turn those numbers into the same type under the covers.

Presumably it's the larger type, and then they try to convert it to the left-hand type, which could raise overflow.

I'm asking this because I'm trying to handle arithmetic with mismatched numeric types in saline.

Benjamin Wade

@RespiteSage

Okay, found it

Daniel Worrall

@Daniel-Worrall

yikes, my playground docker container was using 1.2GB of memory

From IRC (bridge bot)

@FromIRC

<Guest15> hello all. i am wondering if variadic functions are supported for crystal functions and procs. ive tried playing around with VaList and viewing the specs around it, but i cant seem to make sense of it. does anyone happen to have an example of passing multiple arguments via variadic functions with crystal?

Quinton Miller

@HertzDevil

crystal defs: https://crystal-lang.org/reference/syntax_and_semantics/splats_and_tuples.html

c funs: no (crystal-lang/crystal#214)

maybe you could use valist exactly like c i don't know

Lance Dillon

@riffraff169

just a question: c varargs no, but is it possible to link to a c function that accepts varargs, but you dont pass varargs...so you would create a crystal function for each variant you want...

if you only need one, you would create the static (sort of) crystal function, pass the data to the varargs c function statically, but the c function would do its varargs thing with your data...

i hope that was clear

George Dietrich

@Blacksmoke16

From IRC (bridge bot)

@FromIRC

<Guest64> hey, is it possible for a crystal macro to edit other portions of the code base when called? for example, i have a macro that defines a proc, but i also want to append the procs name to a case clause in another def method. so that each time the macro is called, it creates the proc, but also adds it to the list of when clauses

<Guest64> https://pastebin.com/sPpFLwhP is a quick little mock up

Lance Dillon

@riffraff169

you could probably have a macro create another source file to be added to the list of files to be compiled and linked...that file will define the method

maybe

From IRC (bridge bot)

@FromIRC

<Guest64> hmm, i will try exploring that avenue. i was also thinking perhaps a macro calling a macro might work, in which the second macro might define the when clause. id have to play with it later

<Guest64> as a side question: is there a cleaner way to create default args

<Guest64> from a splat of types for a macro? for example if *types contains

<Guest64> {Int32, Int32}, when the macro defines a definition i use: def my_def({%

<Guest64> for type, index in args %}arg{{index}} : {{type}},{% end %}) which

<Guest64> expands to def my_def(arg0 : Int32, arg1 : Int32)

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

From IRC (bridge bot)

@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.

From IRC (bridge bot)

@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

From IRC (bridge bot)

@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?

From IRC (bridge bot)

@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

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