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: lbfgsb.m
    path of file: ./repos/mdtoolbox/mdtoolbox
    
    the code of the file until where you have to start completion: function [x,f,info] = lbfgsb( fcn, l, u, opts )
% x = lbfgsb( fcn, l, u )
%   uses the lbfgsb v.3.0 library (fortran files must be installed;
%       see compile_mex.m ) which is the L-BFGS-B algorithm.
%   The algorithm is similar to the L-BFGS quasi-Newton algorithm,
%   but also handles bound constraints via an active-set type iteration.
%   This version is based on the modified C code L-BFGS-B-C, and so has 
%   a slightly different calling syntax than previous versions.
%
%  The minimization problem that it solves is:
%       min_x  f(x)     subject to   l <= x <= u
%
% 'fcn' is a function handle that accepts an input, 'x',
%   and returns two outputs, 'f' (function value), and 'g' (function gradient).
%
% 'l' and 'u' are column-vectors of constraints. Set their values to Inf
%   if you want to ignore them. (You can set some values to Inf, but keep
%   others enforced).
%
% The full format of the function is:
% [x,f,info] = lbfgsb( fcn, l, u, opts )
%   where the output 'f' has the value of the function f at the final iterate
%   and 'info' is a structure with useful information
%       (self-explanatory, except for info.err. The first column of in
    
function str = findTaskString( taskInteger )
% See the #define statements in lbfgsb.h
switch taskInteger
case 209
    str = 'ERROR: N .LE. 0';
case 210
    str = 'ERROR: M .LE. 0';
case 211
    str = 'ERROR: FACTR .LT. 0';
case 3
	str = 'ABNORMAL_TERMINATION_IN_LNSRCH.';
case 4
	str = 'RESTART_FROM_LNSRCH.';
case 21
	str = 'CONVERGENCE: NORM_OF_PROJECTED_GRADIENT_<=_PGTOL.';
case 22
	str = 'CONVERGENCE: REL_REDUCTION_OF_F_<=_FACTR*EPSMCH.';
case 31
	str = 'STOP: CPU EXCEEDING THE TIME LIMIT.';
case 32
	str = 'STOP: TOTAL NO. of f AND g EVALUATIONS EXCEEDS LIM.';
case 33
	str = 'STOP: THE PROJECTED GRADIENT IS SUFFICIENTLY SMALL.';
case 101
	str = 'WARNING: ROUNDING ERRORS PREVENT PROGRESS';
case 102
	str = 'WARNING: XTOL TEST SATISIED';
case 103
	str = 'WARNING: STP = STPMAX';
case 104
	str = 'WARNING: STP = STPMIN';
case 201
	str = 'ERROR: STP .LT. STPMIN';
case 202
	str = 'ERROR: STP .GT. STPMAX';
case 203
	str = 'ERROR: INITIAL G .GE. ZERO ';
case 204
	str = 'ERROR: FTOL .LT. ZERO';
case 205
	str = 'ERROR: GTOL .LT. ZERO';
case 206
	str = 'ERROR: XTOL .LT. ZERO';
case 207
	str = 'ERROR: STPMIN .LT. ZERO';
case 208
	str = 'ERROR: STPMAX .LT. STPMIN';
case 212
	str = 'ERROR: INVALID NBD';
case 213
	str = 'ERROR: NO FEASIBLE SOLUTION';
    otherwise
        str = 'UNRECOGNIZED EXIT FLAG';
end