change Predict to const function

src/mlpack/methods/softmax_regression/softmax_regression.hpp

@@ -111,7 +111,7 @@ class SoftmaxRegression
    * @param testData Matrix of data points for which predictions are to be made.
    * @param predictions Vector to store the predictions in.
    */
-  void Predict(const arma::mat& testData, arma::vec& predictions);
+  void Predict(const arma::mat& testData, arma::vec& predictions) const;
 
   /**
    * Computes accuracy of the learned model given the feature data and the

src/mlpack/methods/softmax_regression/softmax_regression_impl.hpp

@@ -58,7 +58,7 @@ SoftmaxRegression<OptimizerType>::SoftmaxRegression(
 
 template<template<typename> class OptimizerType>
 void SoftmaxRegression<OptimizerType>::Predict(const arma::mat& testData,
-                                               arma::vec& predictions)
+                                               arma::vec& predictions) const
 {
   // Calculate the probabilities for each test input.
   arma::mat hypothesis, probabilities;