Public Domain Copyright

Author: zoziha

.gitignore

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+# fpm files
+build*
+API-doc/*
+
+# vscode files
+.vscode/*

README.md

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+# FFTPACK 4.0 PUBLIC DOMAIN COPYRIGHT
+FFTPack aims to provide an easily usable package of functions using FFTPack library (Fortran 77).
+
+## Getting started
+```bash
+git clone https://github.com/certik/fftpack.git
+cd fftpack
+git branch fftpack4.0
+```
+## Dependencies
+
+Git and [fortran-lang/fpm](https://github.com/fortran-lang/fpm)
+
+### Supported Compilers
+The following combinations are tested on the default branch of `fftpack`:  
+|Name|Vesrion|Platform|Architecture|  
+|---|---|---|---|  
+|GCC Fortran(MSYS2)|10|Windows 10|x86_64|  
+
+### Build with [fortran-lang/fpm](https://github.com/fortran-lang/fpm)
+Fortran Package Manager (fpm) is a great package manager and build system for Fortran.   
+You can build using provided `fpm.toml`:
+```bash
+fpm build
+fpm test
+```
+To use `fftpack` within your `fpm` project, add the following to `fpm.toml` file:
+```toml
+[dependencies]
+fftpack = { git="https://github.com/certik/fftpack.git", branch="fftpack4.0" }
+```
+
+## Links
+[netlib/dfftpack1.0(fftpack4.0)](http://www.netlib.org/fftpack/)

doc/dfftpack-doc/doc.double.md

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+This documents the changes done by HCP to make fftpack into dfftpack
+
+(1) Renamed all files corresponding to subroutines in the API
+    i.e. ones documented as callable by the luser. Names chosen to match
+    the ones in libsunperf.
+
+(2) Inserted  IMPLICIT DOUBLE PRECISION (A-H,O-Z) after every
+    subroutine statement. This makes everything that used to be a real 
+    into a double.
+
+(3) Replaced floating constants with Double Prec. constants. All
+    0. become 0.D0 etc and PI, SQRT(2) etc. expanded to dble prec.
+ 
+(4) Replaced DIMENSION FOO(1) with DIMENSION FOO(*) where foo
+    is an array argument of a subroutine. I only did this in the places 
+    where g77 notices it, so the compile looks cleaner.
+
+(5) Replaced COMPLEX with DOUBLE COMPLEX. Now, this is not standard 
+    fortran 77, so the whole thing may fall apart if you have a VERY
+    vanilla Fortran 77 compiler. On the other hand, the only place a 
+    complex is _declared_ as such is in the test program. If you don't have 
+    DOUBLE COMPLEX my guess is that the library will work, except for 
+    the routines  ZFFTI, ZFFTB and ZFFTF.
+
+(6) Updated the file doc