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 Pari/Gp is a software package for computer-aided number theory. The GPL'd package is under active development. For an introduction, see the Pari . A short introduction to Pari on Linux . On Unix (Solaris, Linux or OS 10) Pari is started in a terminal with "gp". On Windows or Mac OS 9, Pari/Gp is an application. Pari is an excellent calculator with infinite accuracy, useful to solve equations, find roots of polynomials etc: ``` log(234234) 12341239417623941782346*123412341234123412341234 factor(111111111111111111111111111111111111111111111111111111111111111111111111111111111) factor(1+2*x+x^2) 10! solve(x=0,1,cos(x)-x) polroots(x^3+x^2-2*x-2) ``` Pari knows calculus, can find Taylor series, find integrals, plot functions, find the derivatie of a function, sum a series. In that case we switched to 200 digit accuracy: ``` Ser( (1-x)^(-1) ) intnum(t=0,2*Pi,sin(exp(I*t))) plot(x=0,2*Pi,sin(x)) f(x)=sin(cos(x)) f'(x) p 200 4*sumalt(k=0,(-1)^k/(2*k+1)) ``` To work with complex numbers, just note that I is the the imaginary i. ``` (1+I)*(1-I) abs(1+I) ``` For doing linear algebra, like solving a linear system A x=b or find the determinant of a matrix A: ``` A=matrix(3,3,i,j,i/j+j/(i+1)*2+3) b=[0;1] gauss(A,b) matdet(A) ``` It allows programming ``` f(n)=if(n==0,1,if(n==1,1,f(n-1)+2*f(n-2))) f(20) ``` An example of a program is pollard.gp , which factors numbers using the Pollard rho method. In Pari, read the file with ``` pollard.gp ``` More Pari documentation can be found here .

 Simplicity, Clarity, Generality B.W. Kernighan, R. Pike, in "The Practice of Programming".