You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: g_QLearning.m
    path of file: ./repos/VBA-toolbox/demos/_models
    
    the code of the file until where you have to start completion: function  [gx, dgdx, dgdp] = g_QLearning (x, P, u, in)
% // VBA toolbox //////////////////////////////////////////////////////////
%
% [gx, dgdx, dgdP] = g_QLearning (x, P, u, in)
% softmax decision rule for Q-learning (N-armed bandit task)
%
% IN:
%   - x: Q-values
%   - P: (1) inverse (log-) temperature 
%        (2) bias
%   - u: (idx(1)) index of 0 coded cue
%        (idx(2)) index of 1 coded cue
%   - in: 
%       - idx: position of inputs indicating Q-values to use
% OUT:
%   - gx : P(y = 1|x)

% /////////////////////////////////////////////////////////////////////////

% Get parameter values
% =========================================================================

% inverse temperature
beta = exp (P(1)); % exp: [-Inf,Inf] -> [0 Inf]

% offset

    
function  [gx, dgdx, dgdp] = g_QLearning (x, P, u, in)
% // VBA toolbox //////////////////////////////////////////////////////////
%
% [gx, dgdx, dgdP] = g_QLearning (x, P, u, in)
% softmax decision rule for Q-learning (N-armed bandit task)
%
% IN:
%   - x: Q-values
%   - P: (1) inverse (log-) temperature 
%        (2) bias
%   - u: (idx(1)) index of 0 coded cue
%        (idx(2)) index of 1 coded cue
%   - in: 
%       - idx: position of inputs indicating Q-values to use
% OUT:
%   - gx : P(y = 1|x)

% /////////////////////////////////////////////////////////////////////////

% Get parameter values
% =========================================================================

% inverse temperature
beta = exp (P(1)); % exp: [-Inf,Inf] -> [0 Inf]

% offset
try
    const = P(2);
catch 
    const = 0;
end