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 17989 days, 13 hours, 19 minutes ago.