Exponential integral Ei(x) is defined as a principal value of an integral

Exponential integral En(x) is defined as

ExponentialIntegralEI subroutine calculates Ei(x) using piecewise rational approximation. En(x) is calculated by using the ExponentialIntegralEN subroutine. This subroutine uses series expansion, continuous fraction approximation or asymptotic approximation depending on the values of x and n.

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C#

C# 1.0 source.
expintegrals.csharp.zip - Exponential integrals Ei(x) and En(x)

C++

C++ source.
expintegrals.cpp.zip - Exponential integrals Ei(x) and En(x)
ablas.zip - optimized basic linear algebra subroutines with SSE2 support (for C++ sources only)

Delphi

Delphi source.
Can be compiled under FPC (in Delphi compatibility mode).
expintegrals.delphi.zip - Exponential integrals Ei(x) and En(x)

Visual Basic 6

Visual Basic 6 source.
expintegrals.vb6.zip - Exponential integrals Ei(x) and En(x)

Zonnon ^beta

Zonnon source.
Zonnon is an experimental language developed at ETH Zurich.
See www.zonnon.ethz.ch for more information.
expintegrals.zonnon.zip - Exponential integrals Ei(x) and En(x)