listing the digits of pi in an efficient way in Julia

Question

I am trying to list the digits of pi in order using Julia

b = 1
n = 10^b
println(3.0)

for i in 0:20
    println(-floor(π*n^(i))*10 + floor(π*n^(i+1)))
        end

This code works for the first 15 iterations. However, after that I receive negative valued numbers, which obviously makes no sense

3.0
1.0
4.0
1.0
.
.
.        
0.0
-5.795215566461698e19
2.8976077832308487e20
-2.318086226584679e20

My guess is that the n^i term is too big to handle, making my code extremely inefficient. Is there a more efficient way, lets say to list the first 1000 digits of pi?

Answer 1

Use setprecision such as:

julia> setprecision(4000) do
           BigFloat(π)
       end
3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132823066470938446095505822317253594081284811174502841027019385211055596446229489549303819644288109756659334461284756482337867831652712019091456485669234603486104543266482133936072602491412737245870066063155881748815209209628292540917153643678925903600113305305488204665213841469519415116094330572703657595919530921861173819326117931051185480744623799627495673518857527248912279381830119491298336733624406566430860213949463952247371907021798609437027705392171762931767523846748184676694051320005681271452635608277857713427577896091736371787214684409012249534301465495853710507922796892589235420199561121290219608640344181598136297747713099605187072113499999983729780499510597317328160963185950244594553469083026425223082533446850352619311881710100031378387528865875332083814206171776691473035982534904287554687311595628638823537875937519577818577805321712268066130019278766111959092164201989380952572010654858632788659361533818279682303019520353018529689957736225994138912497217752834791315155748572424541506959508295331168617278558890

In your code similarly you could use BigFloats and BigInts combined with setprecision.