iau1980.frink

View or download iau1980.frink in plain text format


// This program reads coefficients for nutation from the file IAU1980.txt
// and converts them to a Frink expression for use in the sun.frink library
// for astronomical code.
// This produces high-accuracy figures for the nutation of the earth.

psi =     "   deltapsi = 0.0001 arcsec ("
epsilon = "   deltaepsilon = 0.0001 arcsec ("

for line = lines["file:IAU1980.txt"]
{
   [D, M, MP, F, Omega, deltapsi, deltapsiT, deltaepsilon, deltaepsilonT] = split[%r/\t/, line]

   coeffPsi = fmtCoeff[deltapsi, deltapsiT]
   coeffEpsilon = fmtCoeff[deltaepsilon, deltaepsilonT]
   arg = fmt[D, "D"]
   arg = arg + fmt[M, "M"]
   arg = arg + fmt[MP, "MP"]
   arg = arg + fmt[F, "F"]
   arg = arg + fmt[Omega, "Omega"]
   if (coeffPsi != "")
      psi = psi + " + ($coeffPsi) sin[$arg]";
   if (coeffEpsilon != "")
      epsilon = epsilon + " + ($coeffEpsilon) cos[$arg]";
}

psi = psi + ")"
epsilon = epsilon + ")"

println[psi]
println[epsilon]

fmt[x, char] := 
{
   x = eval[x]

   if (x == 1)
      return " + $char"

   if x > 0
      return " + $x $char"

   if x < 0
      return " -" + (-x) + " $char"

   return ""
}

fmtCoeff[t0, t1] := 
{
   str = ""
   t0 = eval[t0]
   t1 = eval[t1]
   if (t0 != 0)
      str = "$t0"
   if (t1 != 0)
      str = str + " + $t1 T"
   return str
}


View or download iau1980.frink in plain text format


This is a program written in the programming language Frink.
For more information, view the Frink Documentation or see More Sample Frink Programs.

Alan Eliasen was born 17590 days, 6 hours, 53 minutes ago.