Represent very many decimals of an irrational number

Question

I want to represent A LOT of decimal digits of a irrational number like sqrt(2) or cos(23). For example i need to show the first 100,000 decimal digits of sqrt(2) , this is possible in c#?, how i can do this?

It depends on the number - if you can find a taylor series or other method to calculate the number then yes, it's possible. Not _simple_ but _possible_. — D Stanley, Dec 20 '16 at 20:50
possible duplicate of http://stackoverflow.com/questions/10359372/is-there-a-bigfloat-class-in-c — Georg, Dec 20 '16 at 20:52
with build in type? Nope. Custom calculation, yes. But whether you want to take it that far is another question — Steve, Dec 20 '16 at 20:55
it is simple. go to wolframalpha and get everything you want. for example https://www.wolframalpha.com/input/?i=cos+23 — M.kazem Akhgary, Dec 20 '16 at 20:56

score 0 · Answer 1 · edited May 23 '17 at 12:32

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AFAIK (please any reader correct me if I'm wrong) there's no built in type for that. However, as workarounds:

An answer here with some system for it.
Use BigInteger and do the rest yourself.
Use BigRational mentioned here.

edited May 23 '17 at 12:32

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answered Dec 20 '16 at 21:01

ispiro

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score 0 · Accepted Answer · answered Mar 05 '17 at 23:19

I solved this problem with the GNU MPFR Library , specifically with a c# wrapper by Luboš Hemala, then i code an algorithm for Nth roots.

  public static void Nth_Root(ref StringBuilder Output,ref long ComaPos, String Radicand, String Index, ulong Precision,int NBase)
        {
            // (1 / Input Index) = N_Index
            Decimal D_index = Convert.ToDecimal(Index, new CultureInfo("en-US"));
            D_index = 1.00m / D_index;
            String N_Index = D_index.ToString(new CultureInfo("en-US"));
            //Calculating Precision
            Decimal Prec02 = Precision * 3.31125m;
            ulong Prec03 = Convert.ToUInt64(Prec02);
            int Prec04 = Convert.ToInt32(Precision);
            // Declaring MPFR Variables
            var Rad = new mpfr_struct();
            var Ind = new mpfr_struct();
            var Res = new mpfr_struct();
            MPFRLibrary.mpfr_init2(Rad, 1000LU);
            MPFRLibrary.mpfr_init2(Ind, 1000LU);
            MPFRLibrary.mpfr_init2(Res, Prec03);
            //String inputs to MPFR variables
            MPFRLibrary.mpfr_set_str(Rad, Radicand, 10, (int)Rounding.AwayFromZero);
            MPFRLibrary.mpfr_set_str(Ind, N_Index, 10, (int)Rounding.AwayFromZero);
            //Calculating Power of Radicand to the N_Index
            var sb = new StringBuilder(Prec04);
            long expptr = 0;
            MPFRLibrary.mpfr_pow(Res, Rad, Ind, (int)Rounding.AwayFromZero);
            //Converting MPFR Result to StringB
            MPFRLibrary.mpfr_get_str(sb, ref expptr, NBase, 0, Res, (int)Rounding.AwayFromZero);
            Output = sb;
            ComaPos = expptr;
        }

Represent very many decimals of an irrational number

2 Answers2