%%HP: T(3)A(R)F(.);
@ Psychrometric equation solved in RPL - Version 1.1
@ Pushes the vapour mixing ratio in kg/kg in the stack.
@ Only tested on a HP 50g.
\<<
  "Psychrometric equation"
{ {} 
  { "Dry bulb temperature:" "Dry bulb temperature in \^oC" 0.}
  { "Wet bulb temperature:" "Wet bulb temperature in \^oC" 0.}
  { "            Pressure:" "Pressure in hPa" 0.}}
  {1 0} {NOVAL NOVAL 1000.} DUP
  INFORM
  \<<
    OBJ\-> DROP
    \<<  @ Local procedure to calculate saturated vapour mixing ratio
         @ from the temperature on stack position 1 and pressure on 2
      DUP 17.67 * SWAP 243.5 + / EXP 6.112 *   @ Now contains e_s(T)
      DUP 3 ROLL
      SWAP - 1.61 * /
    \>>  \-> Td Tw P0 TtoR
    \<<  
      @ c_pd + c_pv r_vs(Tw):
      P0 Tw TtoR EVAL DUP 1859.0 * 1004.0 +
      @ L(Td) = L(0)-Td (c_pl-c_pv):
      2.501E06 Td 4218.0 1859.0 - * -
      @ Psychrometric equation:
      / Tw Td - * + "r" \->TAG DUP DUP 1000.0 * -2 RND
      SWAP P0 Td TtoR EVAL / 100 *  0 RND R\->I
      2 \->LIST
    \>>
    "Psychrometric equation"
  { {} 
    { "Specific humidity:" "Specific humidity (g/kg)" 0}
    { "Relative humidity:" "Relative humidity (%)" 10} }
    {1 0} 4 ROLL DUP
    INFORM
    \<< DROP\>> IFT
  \>> IFT
\>>