#! /usr/bin/python -t 
# _*_ coding: iso-8859-1 _*_
# Last edited on 2009-07-13 23:11:43 by stolfi

# Last edited on 2009-07-13 22:16:35 by stolfi

def build_formula_carbon_suboxide_polymer(pat) :
  "Builds a formula for a linear carbon suboxide polymer described by {pat}.\n" \
  "\n" \
  "  Pat is the alist of strings. Each string describes a C3O2 unit" \
  " of the polymer, from left to right.  Each unit can be:\n" \
  "\n" \
  "    'L{D}' = left terminator. \n" \
  "    '{N}{X}H{D}{Y}' = {N} copies of the hemimer. \n" \
  "    'R{D}' = right terminator. \n" \
  "    '{N}g' = a gap of {N} half-bonds. \n" \
  "\n" \
  "  The modifier {D} for a terminator 'L' or 'R' is either 'u' (ketene" \
  " at top) or 'd' (ketene at bottom); for a hemimer sequence it applies" \
  " to the first hemimer of the sequence, also 'u' (carbonyl on top) or 'd' (carbonyl at bottom). \n" \
  "\n" \
  "  The modifiers {X} and {Y} for a hemimer sequence apply to the left" \
  " side of the first unit and the right side of the last unit," \
  " respectively.  They can be either 's' (straight horizontal connections)" \
  " or 'b' (connections bent to accept a terminator)."
  
  fm = MFormula();
  
  sb = fm.bond_length(1.0);
  
  dX = 0.0; # Horizontal displacement for next unit.
  
  flip = 0; # Next unit must be flipped/rotated.
  
  Tang = carbon_suboxide_polymer_terminator_angle();
  
  for i in range(pat) :
    item = pat[i]; # Code of next unit or uit sequence.
    # Extract and delete the repeater {N} if any:
    N = int(re.findall(r'^(\d+\)', item));
    if N == None : N = 0;
    item = re.sub(r'^(\d+\)', '', item);
    # Operations:
    if item == 'g' :
      # Gap:
      dX = dX + 0.5*N*sb;
    elif re.match(r'^[LR]', item) :
      # Left/right terminator:
      # Extract the inversion flag {D}:
      D = re.findall(r'([ud])$', item)
      if D == None : D = 'u';
      item = re.sub(r'([ud])$', '', item);
      if D == 'u' :
        Rinv = 0;
      elif D == 'd' :
        Rinv = 1;
      else :
        assert FALSE;
        
      if 
        
      if (i == len(pat)-1) or (i == 
      
      fu = build_formula_poly_carbon_suboxide_terminator(".",Rang,Rinv);
    
  
  fu = build_formula_poly_carbon_suboxide_monomer();

  sb = fu.bond_length(1.0); # Relative length of single bonds.
  dx = 3.0*sb;

  # Assemble the three full units:
  k0 = fm.add_subformula(fu, 0, 0, [0*dx,0]);
  k1 = fm.add_subformula(fu, 0, 0, [1*dx,0]);
  k2 = fm.add_subformula(fu, 0, 0, [2*dx,0]);

  return fm;