Significant figures printing in GP.

[R J Cano <bacanocano@gmail.com>]

Dear PARI users.

Please.

Is this code a neat way of displaying real numbers rounded up to
certain quantity of significant figures?,

sigfig(a,{b=%})={if(type(b)==type(3.141592),my(x=digits(truncate(b*10^default(realprecision)))[1..a+1]);x[a]+=(x[a+1]>4);return(x[1..a]))}

Admittedly i never tried that before in automated way. it seems to
display correct results, but im not clear if there is an easier way of
achieving the same.

For instance, let's assume certain calculation involving only real
numbers in the final result, yields

x=3.00002575

And we are asked to represent it with only 7 significant figures. So,
before anything else, we call:

xr=sigfig(7)

Then the expected result must be printed:

3.000026

Again, the thing im questioning here, is the code shown above... after
reviewing that topic on significant figures, it simply was written
such routine just as to mimic the precise way a human does it by hand.

Thanks in advance.
Best wishes,

--Remy