New += and *= syntaxes in “endval(learnt_in=…)” blocks

doc/manual/source/the-model-file.rst

@@ -3915,6 +3915,7 @@ and ``endval`` blocks which are given a special ``learnt_in`` option.
         end;
 
     This syntax means that:
+
       - from the perspective of period 1, ``x`` is expected to be equal to 1 in
         periods 1 and 2, to 1.2 in periods 3 and 4, and to 1.4 in period 5;
       - from the perspective of periods 2 (and 3), ``x`` is expected to be
@@ -3925,23 +3926,40 @@ and ``endval`` blocks which are given a special ``learnt_in`` option.
 
 .. block:: endval(learnt_in=INTEGER) ;
 
-    |br| The ``endval(learnt_in=INTEGER)`` can be used to specify temporary
-    shocks that are learnt in a specific period.
+    |br| The ``endval(learnt_in=INTEGER)`` can be used to specify terminal
+    conditions that are learnt in a specific period.
 
     Note that an ``endval(learnt_in=1)`` block is equivalent to a regular
     :bck:`endval` block.
 
+    It is possible to express the terminal condition by specifying the level of
+    the exogenous variable (using an equal symbol, as in a regular
+    :bck:`endval` blocks without the ``learnt_in`` option). But it is also
+    possible to express the terminal condition as an addition to the value
+    expected from the perspective of the previous previous period (using the
+    ``+=`` operator), or as a multiplicative factor over that previously
+    expected value (using the ``*=`` operator).
+
     *Example*
 
     ::
 
-        endval(learnt_in = 2);
+        endval(learnt_in = 3);
           x = 1.1;
+          y += 0.1;
+          z *= 2;
         end;
 
-    This syntax means that, in period 2, the agents learn that the terminal
-    condition for ``x`` will be 1.1. This value will be the realized one,
-    unless there is another ``endval(learnt_in=p)`` block with ``p>2``.
+    This syntax means that, in period 3, the agents learn that:
+
+      - the terminal condition for ``x`` will be 1.1;
+      - the terminal condition for ``y`` will be 0.1 above the terminal
+        condition for ``y`` that was expected from the perspective of period 2;
+      - the terminal condition for ``z`` will be 2 times the terminal condition
+        for ``z`` that was expected from the perspective of period 2.
+
+    Those values will be the realized ones, unless there is another
+    ``endval(learnt_in=p)`` block with ``p>3``.
 
 .. command:: perfect_foresight_with_expectation_errors_setup ;
              perfect_foresight_with_expectation_errors_setup (OPTIONS...);

matlab/perfect-foresight-models/perfect_foresight_with_expectation_errors_setup.m

@@ -90,7 +90,17 @@ else
             idx = find([M_.learnt_endval.learnt_in] == p);
             for i = 1:length(idx)
                 j = idx(i);
-                oo_.pfwee.terminal_info(M_.learnt_endval(j).exo_id, p) = M_.learnt_endval(j).value;
+                exo_id = M_.learnt_endval(j).exo_id;
+                switch M_.learnt_endval(j).type
+                    case 'level'
+                        oo_.pfwee.terminal_info(exo_id, p) = M_.learnt_endval(j).value;
+                    case 'add'
+                        oo_.pfwee.terminal_info(exo_id, p) = oo_.pfwee.terminal_info(exo_id, p) + M_.learnt_endval(j).value;
+                    case 'multiply'
+                        oo_.pfwee.terminal_info(exo_id, p) = oo_.pfwee.terminal_info(exo_id, p) * M_.learnt_endval(j).value;
+                    otherwise
+                        error('Unknown type in M_.learnt_endval')
+                end
             end
         end
         oo_.pfwee.shocks_info(:, :, p) = oo_.pfwee.shocks_info(:, :, p-1);

preprocessor

@@ -1 +1 @@
-Subproject commit 8c07fb5e4310b2ec2988dc62256e1cf0971c05dd
+Subproject commit 3a820fffa2f7291be5732c33bde552526eab1602

tests/deterministic_simulations/pfwee_learnt_in.mod

@@ -50,7 +50,7 @@ shocks(learnt_in = 3);
 end;
 
 endval(learnt_in = 3);
-  x = 1.2;
+  x += 0.1;
 end;
 
 // Dummy block, that will be overwritten by the next one
@@ -67,7 +67,7 @@ shocks(learnt_in = 6, overwrite);
 end;
 
 endval(learnt_in = 6);
-  x = 1.1;
+  x *= 0.75;
 end;
 
 perfect_foresight_with_expectation_errors_setup(periods = 7);
@@ -106,7 +106,7 @@ oo_.exo_simul = [ saved_exo; oo_.exo_simul ];
 // Information arriving in period 3 (temp shocks + permanent shock in future)
 oo_.exo_simul(4,1) = 1.4;
 oo_.exo_simul(8,1) = 1.5;
-oo_.exo_steady_state = 1.2;
+oo_.exo_steady_state = 1.1+0.1;
 oo_.exo_simul(end, 1) = oo_.exo_steady_state;
 oo_.steady_state = evaluate_steady_state(oo_.steady_state, M_, options_, oo_, true);
 oo_.endo_simul(:, end) = oo_.steady_state;
@@ -122,7 +122,7 @@ oo_.exo_simul = [ saved_exo; oo_.exo_simul ];
 // Information arriving in period 6 (temp shocks + permanent shock)
 oo_.exo_simul(7,1) = 1*0.8;
 oo_.exo_simul(8,1) = 1.5*0.8;
-oo_.exo_steady_state = 1.1;
+oo_.exo_steady_state = (1.1+0.1)*0.75;
 oo_.exo_simul(end, 1) = oo_.exo_steady_state;
 oo_.steady_state = evaluate_steady_state(oo_.steady_state, M_, options_, oo_, true);
 oo_.endo_simul(:, end) = oo_.steady_state;