I don't think you can do this as a macro, you want to use a function
instead wrapping multiple @printf's as you stated.
the behavior you are asking for is to partially evaluate the string
function at compile time (hack)
macro myprintf(args...)
if length(args) == 0
error("@myprintf: called with zero arguments")
end
if isa(args[1], String) || (isa(args[1], IO) && isa(args[1], String))
:(@printf($(args...)))
else
local io, func, fargs
if isa(args[1], Expr)
io = :(Base.STDOUT)
func = args[1].args[1]
fargs = args[1].args[2:end]
elseif (isa(args[1], IO) && isa(args[2], Expr))
io = args[1].args[1]
func = args[1].args[2]
fargs = args[1].args[3:end]
else
error("better message here")
end
for i in 1:length(fargs)
if isa(fargs[i], Symbol)
fargs[i] = getfield(current_module(), fargs[i])
end
end
fmt_string = apply(getfield(Base, func), fargs...)
:(@printf($io, $fmt_string, $(args[2:end]...)))
end
end
however this does not work at all with local scope.
julia> a = "This is "
"This is "
julia> b = "a test: %d"
"a test: %d"
julia> @myprintf(string(a, b), 10)
This is a test: 10
julia> let a = "test1 ", b = "test2 %d"
@myprintf(string(a, b), 10)
end
This is a test: 10
julia>
Best,
Jake
On Sunday, February 2, 2014 6:53:04 PM UTC-5, John Myles White wrote:
>
> Hi Alexander,
>
> I’m not aware of a way to do this, but would also like to know how to do
> it.
>
> — John
>
> On Feb 2, 2014, at 5:52 AM, Alexander Samoilov <
> [email protected] <javascript:>> wrote:
>
> > Hello,
> >
> > I have a format string - a "%Fmt" literal for @printf() and it is too
> large, so would like to concatenate it from chunks,
> > say using string("chunk 1 ", " chunk 2 ", " chunk 3 ")
> >
> > @printf() disallow to do it as requires a string literal, but string()
> is a function and the produced string variable cannot be checked vs.
> @printf() args.
> >
> > julia> @printf(string("abc ", " def ", " ggg "))
> > ERROR: first or second argument must be a format string
> >
> > Looks this is intentionally to have an opportunity to check format
> string vs. parameters (at least check number of args).
> >
> > BTW, C allows gluing of a few consecutive strings, e.g. "abc " " def "
> " ggg " into one string literal, though it doesn't look very aesthetic.
> >
> > Is it possible for Julia to construct a format string somehow and feed
> it to @printf() or this is impossible in principle
> > and several invocations of @printf() should be used as workaround?
> >
> > Thanks,
> > Alexander
>
>
