@printf does not accept * for passing precision or width as argument

[Maxpxt]

The docs on @printf state that it follows C-style formatting as specified here. This spec allows for * to be used in the precision and/or width positions to indicate that the precision and/or width will be passed as additional arguments preceding the value to be formatted. Example (in C):

printf("%.*f", 2, 3.141);   // prints "3.14"
printf("%.*f", 4, 3.141);   // prints "3.1410"

Currently (Julia 1.6.1), @pritnf does not recognize such format specifiers. @printf "%.*f" 2 3.141 fails with ArgumentError: invalid format string: '%.*f', invalid type specifier: '*'.

I don't know whether not supporting this is intended behavior or not. If it is, the docs should be updated to say how Julia's @printf differs from the C-style spec.

Here is an example where having this would be useful:

function format_float_without_trailing_zeros(x, precision)
    rstrip(rstrip((@sprintf "%.*f" precision x), '0'), '.')
end

format_float_without_trailing_zeros(3.1415, 2)  # "3.14"
format_float_without_trailing_zeros(3.0, 2)     # "3"

[bicycle1885]

#40105 addresses this issue (Fmt.jl supports that feature, btw).

[Maxpxt]

Oh, I did not think to search the PRs. Should the issue be left open? (Thanks for the tip!)

[bicycle1885]

Should the issue be left open?

Yes, I think it should.