Please don't do this – or if you do and your program is amazingly slow, then consider yourself warned. You can define a custom formatting function pretty easily:
julia> fmt = "%8.1e" "%8.1e" julia> @eval dofmt(x) = @sprintf($fmt, x) dofmt (generic function with 1 method) julia> dofmt(1) " 1.0e+00" julia> dofmt(123.456) " 1.2e+02" The difference is that you compile the function definition with eval *once* and then call it many times, rather than calling eval every time you want to print something. On Sun, Apr 13, 2014 at 6:17 PM, Mike Innes <[email protected]> wrote: > It occurs to me that, if you really need this, you can define > > sprintf(args...) = eval(:@sprintf($(args...))) > > It's not pretty or ideal in terms of performance, but it will do the job. > > fmt = "%8.1e" > sprintf(fmt, 3.141) #=> " 3.1e+00" > > On Sunday, 13 April 2014 22:47:12 UTC+1, Dominique Orban wrote: >> >> So what's the preferred Julia syntax to achieve what I meant here: >> >> julia> fmt = "%8.1e"; >> julia> @sprintf(fmt, 3.1415) >> ERROR: first or second argument must be a format string >> >> >> >> On Sunday, April 13, 2014 1:31:57 PM UTC-7, John Myles White wrote: >>> >>> As far as the macro is concerned, the splat isn’t executed: it’s just >>> additional syntax that gets taken in as a whole expression. >>> >>> The contrast between how a function with splatting works and how a macro >>> with splatting works might be helpful: >>> >>> julia> function splat(a, b...) >>> println(a) >>> println(b) >>> return >>> end >>> splat (generic function with 2 methods) >>> >>> julia> splat(1, 2, 3) >>> 1 >>> (2,3) >>> >>> julia> splat(1, [2, 3]...) >>> 1 >>> (2,3) >>> >>> julia> macro splat(a, b...) >>> println(a) >>> println(b) >>> :() >>> end >>> >>> julia> @splat(1, 2, 3) >>> 1 >>> (2,3) >>> () >>> >>> julia> @splat(1, [2, 3]...) >>> 1 >>> (:([2,3]...),) >>> () >>> >>> >>> — John >>> >>> On Apr 13, 2014, at 1:20 PM, Jeff Waller <[email protected]> wrote: >>> >>> > Likewise I am having problems with @sprintf >>> > >>> > Is this because @sprinf is macro? The shorthand of expanding a printf >>> with format the contents of an array is desirable. I would have expected >>> the ... operator to take an array of length 2 and turn it into 2 arguments. >>> > >>> > julia> X=[1 2] >>> > 1x2 Array{Int64,2}: >>> > 1 2 >>> > >>> > julia> @sprintf("%d%d",1,2) >>> > "12" >>> > >>> > julia> @sprintf("%d%d",X...) >>> > ERROR: @sprintf: wrong number of arguments >>> > >>> > julia> @sprintf("%d%d",(1,2)...) >>> > ERROR: @sprintf: wrong number of arguments >>> > >>> > julia> @sprintf("%d",X...) >>> > ERROR: error compiling anonymous: unsupported or misplaced >>> expression ... in function anonymous >>> > in sprint at io.jl:460 >>> > in sprint at io.jl:464 >>> > >>> > julia> macroexpand(quote @sprintf("%d%d",X...) end) >>> > :($(Expr(:error, ErrorException("@sprintf: wrong number of >>> arguments")))) >>> > >>> >>>
