#! /usr/bin/gawk -f
# Last edited on 2014-03-29 21:12:21 by stolfilocal

BEGIN \
  { # Caller must define (with "-v") {D0}, {D1}, {H0}, {H1}, {P0}, {P1}, {Q}, {R}
    # Outputs "-line" commands from {D0-0.5} to {D1+0.5}.
    # The horiz position is {h(D) = H0 + H1*(d-D0)}.
    # The Huobi price is {pH(D) = P0 + P1*Q^(d - D0)}.
    # The Bitstamp price is {pB(D) = pH(D)/R}.
    
    if (DB == "") { arg_error(("must define {DB}")); } # Reference day.
    if (D0 == "") { arg_error(("must define {D0}")); }
    if (D1 == "") { arg_error(("must define {D1}")); }
    if (H0 == "") { arg_error(("must define {H0}")); }
    if (H1 == "") { arg_error(("must define {H1}")); }
    if (P0 == "") { arg_error(("must define {P0}")); }
    if (P1 == "") { arg_error(("must define {P1}")); }
    if (Q == "")  { arg_error(("must define {Q}")); }
    if (R == "")  { arg_error(("must define {R}")); }
    
    N = 4*(D1 - D0) + 5; # Number of plot points.
    
    for (k = 0; k < N; k++)
      { d = D0 + (k - 2)*0.25; # Day number.
        h = int(H0 + H1*(d - DB) + 0.5);
        p = int((P0 + P1*exp(log(Q)*(d - DB)))/R + 0.5);
        if (k > 0) { printf "    -line  \"+\" %5d %5d  %5d %5d \\\n", h_ant, p_ant, h, p; }
        h_ant = h;
        p_ant = p;
      }
  }

#    echo 'd = 27.25; h = 2168 + 120*(d - 24); p = 9881.67 - 263*d; d; h; p; p/6.12'| bc -lq