casadistructs in matlab

casadi_struct2vec.m

function [out] = casadi_struct2vec(s)
  flat = {};
  if isstruct(s)
    for f=fieldnames(s)'
      flat = {flat{:} casadi_struct2vec(s.(f{1}))};
    end
    out = vertcat(flat{:});
  else if iscell(s)
    for i=1:length(s)
       flat = {flat{:} casadi_struct2vec(s{i})};
    end
    out = vertcat(flat{:});
  else
    try
      out = vec(s);
    catch
      import casadi.*
      out = vec(DM(s));
    end
  end
end

casadi_vec2struct.m

function [out] = casadi_vec2struct(s,vec)
  import casadi.*
  assert(isvector(vec))
  try
      vec.sparsity();
  catch
      vec = DM(vec);
  end
  flat = {};
  if isstruct(s)
    out = struct;
    sizes = {0};
    for f=fieldnames(s)'
      n = size(casadi_struct2vec(s.(f{1})),1);
      sizes = {sizes{:} sizes{end}+n};
    end
    comps = vertsplit(vec,sizes);
    i = 1;
    for f=fieldnames(s)'
      out.(f{1}) = casadi_vec2struct(s.(f{1}),comps{i});
      i = i+1;
    end
  else if iscell(s)
    out = cell(size(s));
    sizes = {0};
    for i=1:length(s)
      n = size(casadi_struct2vec(s{i}),1);
      sizes = {sizes{:} sizes{end}+n};
    end
    comps = vertsplit(vec,sizes);
    for i=1:length(s)
      out{i} = casadi_vec2struct(s{i},comps{i});
    end
      else
    out = reshape(vec,size(s));
  end
end

example.m

import casadi.*


% Write all decision variables as a structure
V = struct;
V.x = MX.sym('x');
V.y = MX.sym('y');
V.z = MX.sym('z',4,2);

% Write all constraints as a structure
constr = struct;
constr.initial = V.x+V.y;
constr.z = V.z'*diag([2,4,7,6])*V.z;

lbg = struct;
lbg.initial = 2;
lbg.z = 1*ones(2,2);

ubg = struct;
ubg.initial = 2;
ubg.z = 3*ones(2,2);

% Solve the nlp
e = (2+V.z)*[1+V.x;2-V.y];
f = e'*e + V.z(1).^2;

nlp = struct('x', casadi_struct2vec(V), 'f', f, 'g' , casadi_struct2vec(constr));

solver = nlpsol('solver', 'ipopt', nlp);

args = struct;
args.lbg = casadi_struct2vec(lbg);
args.ubg = casadi_struct2vec(ubg);

res = solver(args);

% Read solution as flat vectors
x_opt = full(res.x);
g_opt = full(res.g);

lambda_opt = full(res.lam_g);

% Create the original structures from these
Vsol = casadi_vec2struct(V,x_opt)

lam = casadi_vec2struct(constr,lambda_opt)

g = casadi_vec2struct(constr,g_opt)