[julia-users] macro to exclude code depending on VERSION

[andrew cooke]

when you're writing code that uses macros, supporting different versions of 
julia seems to be more complex than normal.  in particular, things like:

if VERSION > XX
# code with macros here
end

don't work as expected, because macro expansion occurs before runtime 
evaluation.  so the macros are expenaded whatever version.

given that, i have found this simple macro to be useful;

macro cond(test, block)
if eval(test)
block
end
end

@cond VERSION >= v"0.4" begin
 # code with macros here
end

anyway, my questions are: (1) is the above sensible and (2) does this 
already exist?

thanks,
andrew

Re: [julia-users] macro to exclude code depending on VERSION

[andrew cooke]

ah, great.  i won't make a new package then.  thanks.

On Thursday, 12 November 2015 09:30:21 UTC-3, Yichao Yu wrote:
>
> https://github.com/JuliaLang/julia/issues/7449 
> https://github.com/JuliaLang/Compat.jl/pull/131 
> https://github.com/JuliaLang/julia/issues/5892 
>
> On Thu, Nov 12, 2015 at 7:23 AM, andrew cooke  > wrote: 
> > 
> > when you're writing code that uses macros, supporting different versions 
> of 
> > julia seems to be more complex than normal.  in particular, things like: 
> > 
> > if VERSION > XX 
> > # code with macros here 
> > end 
> > 
> > don't work as expected, because macro expansion occurs before runtime 
> > evaluation.  so the macros are expenaded whatever version. 
> > 
> > given that, i have found this simple macro to be useful; 
> > 
> > macro cond(test, block) 
> > if eval(test) 
> > block 
> > end 
> > end 
> > 
> > @cond VERSION >= v"0.4" begin 
> >  # code with macros here 
> > end 
> > 
> > anyway, my questions are: (1) is the above sensible and (2) does this 
> > already exist? 
> > 
> > thanks, 
> > andrew 
> > 
>

Re: [julia-users] macro to exclude code depending on VERSION

[Yichao Yu]

https://github.com/JuliaLang/julia/issues/7449
https://github.com/JuliaLang/Compat.jl/pull/131
https://github.com/JuliaLang/julia/issues/5892

On Thu, Nov 12, 2015 at 7:23 AM, andrew cooke  wrote:
>
> when you're writing code that uses macros, supporting different versions of
> julia seems to be more complex than normal.  in particular, things like:
>
> if VERSION > XX
> # code with macros here
> end
>
> don't work as expected, because macro expansion occurs before runtime
> evaluation.  so the macros are expenaded whatever version.
>
> given that, i have found this simple macro to be useful;
>
> macro cond(test, block)
> if eval(test)
> block
> end
> end
>
> @cond VERSION >= v"0.4" begin
>  # code with macros here
> end
>
> anyway, my questions are: (1) is the above sensible and (2) does this
> already exist?
>
> thanks,
> andrew
>

Re: [julia-users] macro to exclude code depending on VERSION

[Seth]

...and I just discovered Requires.jl. Fantastic stuff.

On Thursday, November 12, 2015 at 8:55:23 PM UTC-8, Seth wrote:
>
> This could be useful to me :)
>
> I have a couple of functions that require JuMP but I don't want to add 
> JuMP to my REQUIRE file. My usual tactic of checking isdefined(:JuMP) won't 
> work because JuMP uses macros that are evaluated prior to runtime. However, 
> I was unable to make the following code work:
>
> @cond (isdefined(:JuMP)) begin
> function something_that_requires_jump(a...)
> ...
> end # function
> end # macro
>
> Is there an accepted way to do conditional includes of packages that 
> contain macros?
>
> On Thursday, November 12, 2015 at 4:37:43 AM UTC-8, andrew cooke wrote:
>>
>>
>> ah, great.  i won't make a new package then.  thanks.
>>
>> On Thursday, 12 November 2015 09:30:21 UTC-3, Yichao Yu wrote:
>>>
>>> https://github.com/JuliaLang/julia/issues/7449 
>>> https://github.com/JuliaLang/Compat.jl/pull/131 
>>> https://github.com/JuliaLang/julia/issues/5892 
>>>
>>> On Thu, Nov 12, 2015 at 7:23 AM, andrew cooke  
>>> wrote: 
>>> > 
>>> > when you're writing code that uses macros, supporting different 
>>> versions of 
>>> > julia seems to be more complex than normal.  in particular, things 
>>> like: 
>>> > 
>>> > if VERSION > XX 
>>> > # code with macros here 
>>> > end 
>>> > 
>>> > don't work as expected, because macro expansion occurs before runtime 
>>> > evaluation.  so the macros are expenaded whatever version. 
>>> > 
>>> > given that, i have found this simple macro to be useful; 
>>> > 
>>> > macro cond(test, block) 
>>> > if eval(test) 
>>> > block 
>>> > end 
>>> > end 
>>> > 
>>> > @cond VERSION >= v"0.4" begin 
>>> >  # code with macros here 
>>> > end 
>>> > 
>>> > anyway, my questions are: (1) is the above sensible and (2) does this 
>>> > already exist? 
>>> > 
>>> > thanks, 
>>> > andrew 
>>> > 
>>>
>>

Re: [julia-users] macro to exclude code depending on VERSION

[Seth]

This could be useful to me :)

I have a couple of functions that require JuMP but I don't want to add JuMP 
to my REQUIRE file. My usual tactic of checking isdefined(:JuMP) won't work 
because JuMP uses macros that are evaluated prior to runtime. However, I 
was unable to make the following code work:

@cond (isdefined(:JuMP)) begin
function something_that_requires_jump(a...)
...
end # function
end # macro

Is there an accepted way to do conditional includes of packages that 
contain macros?

On Thursday, November 12, 2015 at 4:37:43 AM UTC-8, andrew cooke wrote:
>
>
> ah, great.  i won't make a new package then.  thanks.
>
> On Thursday, 12 November 2015 09:30:21 UTC-3, Yichao Yu wrote:
>>
>> https://github.com/JuliaLang/julia/issues/7449 
>> https://github.com/JuliaLang/Compat.jl/pull/131 
>> https://github.com/JuliaLang/julia/issues/5892 
>>
>> On Thu, Nov 12, 2015 at 7:23 AM, andrew cooke  wrote: 
>> > 
>> > when you're writing code that uses macros, supporting different 
>> versions of 
>> > julia seems to be more complex than normal.  in particular, things 
>> like: 
>> > 
>> > if VERSION > XX 
>> > # code with macros here 
>> > end 
>> > 
>> > don't work as expected, because macro expansion occurs before runtime 
>> > evaluation.  so the macros are expenaded whatever version. 
>> > 
>> > given that, i have found this simple macro to be useful; 
>> > 
>> > macro cond(test, block) 
>> > if eval(test) 
>> > block 
>> > end 
>> > end 
>> > 
>> > @cond VERSION >= v"0.4" begin 
>> >  # code with macros here 
>> > end 
>> > 
>> > anyway, my questions are: (1) is the above sensible and (2) does this 
>> > already exist? 
>> > 
>> > thanks, 
>> > andrew 
>> > 
>>
>