[julia-users] printf format for round-trip Floats

[David P. Sanders]

The simple solutions are often the most elusive! 

[julia-users] printf format for round-trip Floats

['Greg Plowman' via julia-users]

Yes, of course I can!
Thanks David.
That is embarrassingly simple.

[julia-users] printf format for round-trip Floats

[David P. Sanders]

Can't you just use string(x) where x is the Float64? 

[julia-users] printf format for round-trip Floats

['Greg Plowman' via julia-users]

I'm trying to print Float64 with all significant digits, so that 
re-inputting these numbers from output strings will result in exactly 
the same number (is this called a round-trip?)

I understand that Julia uses a grisu algorithm to do this automatically for 
values displayed at REPL and with println().

I'm using @printf to output, so I tried  "%20.17g" as a format specifier 
and this seems to work.

But then I compared this to println() and some numbers vary in the last 
digit (e.g @printf displays 389557.48616130429, whereas println() displays 
389557.4861613043)
So it seems @printf(".17g") sometimes displays an extra unnecessary digit?

Is there another printf format specifer that I can use?

Alternatively, I'm using the following to first convert Float to string, 
and then pass string to @printf:

iobuffer = IOBuffer()
print(iobuffer, x)
str_hits = takebuf_string(iobuffer)
@printf("%20s", x)

but this seems a bit messy.