Added a model with VAR and PAC equation.

examples/1/clean

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+#!/bin/sh
+
+rm -rf example
+rm -f example_dynamic.json example.json example.m example_original.json example_static.json
+rm -f example_dynamic.m example.log example_set_auxiliary_variables.m example_static.m

examples/1/example.mod

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+// --+ options: json=compute +--
+
+var y x z;
+
+varexo ex ey ez;
+
+parameters a_y_1 a_y_2 b_y_1 b_y_2 b_x_1 b_x_2 ; // VAR parameters
+
+parameters beta g e_c_m c_z_1 c_z_2;               // PAC equation parameters
+
+a_y_1 =  .2;
+a_y_2 =  .3;
+b_y_1 =  .1;
+b_y_2 =  .4;
+b_x_1 = -.1;
+b_x_2 = -.2; 
+
+g = .0;
+beta  =  .9;
+e_c_m =  .1;
+c_z_1 =  .7;
+c_z_2 = -.3;
+
+var_model(model_name=toto, eqtags=['eq:x', 'eq:y']);
+
+model;
+
+[name='eq:y']
+y = a_y_1*y(-1) + a_y_2*diff(x(-1)) + b_y_1*y(-2) + b_y_2*diff(x(-2)) + ey ;
+
+[name='eq:x']
+diff(x) = b_x_1*y(-2) + b_x_2*diff(x(-1)) + ez ;
+
+[name='eq:pac']
+diff(z) = e_c_m*(x(-1)-z(-1)) + c_z_1*diff(z(-1)) + c_z_2*diff(z(-2)) + pac_expectation(model_name=pacman, var_model_name=toto, discount=beta, growth=g) + ez;
+
+end;
+
+get_companion_matrix('toto');