Documentation for module splines

Simple splines Splines are fully specified by the interpolation points, except that at the ends, we have the freedom to prescribe the second derivatives. If we know a derivative at an end (exactly), then best is to impose that. Otherwise, it is better to use the "consistent" end conditions: the second derivative is determined such that it is smooth.

source: splines.F
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public Subroutines/Functions:

FUNCTION
REAL(dp)
spline3 (x, y, xnew)
...
SUBROUTINE
spline3ders (x, y, xnew, ynew, dynew, d2ynew)
...

FUNCTIONspline3(x, y, xnew)

...

Return Value ::
REAL(dp)
Arguments:
REAL(dp),
INTENT(in)
:: x(:) ...
REAL(dp),
INTENT(in)
:: y(:) ...
REAL(dp),
INTENT(in)
:: xnew(:) ...

SUBROUTINEspline3ders(x, y, xnew, ynew, dynew, d2ynew)

...

Arguments:
REAL(dp),
INTENT(in)
:: x(:) ...
REAL(dp),
INTENT(in)
:: y(:) ...
REAL(dp),
INTENT(in)
:: xnew(:) ...
REAL(dp),
INTENT(out),
OPTIONAL
:: ynew(:) ...
REAL(dp),
INTENT(out),
OPTIONAL
:: dynew(:) ...
REAL(dp),
INTENT(out),
OPTIONAL
:: d2ynew(:) ...