From 0f72e9ab93d49485a89b41e437ed4cad6fd7dfe6 Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Sat, 10 Apr 2021 18:53:14 +0200
Subject: [PATCH 01/17] Sample if true function added

---
 pysd/py_backend/functions.py             | 87 ++++++++++++++++++++++++
 pysd/py_backend/vensim/vensim2py.py      | 15 ++++
 tests/integration_test_vensim_pathway.py |  2 -
 3 files changed, 102 insertions(+), 2 deletions(-)

diff --git a/pysd/py_backend/functions.py b/pysd/py_backend/functions.py
index 5e326638..77ffdfb1 100644
--- a/pysd/py_backend/functions.py
+++ b/pysd/py_backend/functions.py
@@ -1186,6 +1186,93 @@ def random_uniform(m, x, s):
 
     return np.random.uniform(m, x)
 
+# dictionary to store the values from SAMPLE IF TRUE function
+saved_value = {}
+
+def make_da(rows, cols, initial_value):
+    """
+    Returns a DataArray with the coordinates
+    of the rows and cols.
+    DataArray values are initialized with the initial_value.
+    It is used in SAMPLE IF TRUE function, to create the proper dimension saved value.
+    
+    Parameters
+    ----------
+    rows: float or xarray.DataArray    
+        Represents the row dimension of the new DataArray
+    cols: xarray.DataArray 
+        Represents the col dimension of the new DataArray
+    initial_value: float or xarray.DataArray 
+        Include the values to initialize the new DataArray
+
+    Returns
+    -------
+    A new DataArray with proper rows and cols coordinates,
+    initialized with initial_value
+    
+    """
+    if(isinstance(initial_value,xr.DataArray)):
+        array = np.array([[initial_value.data[e] for i in range(0, len(rows.values))] for e in range(0,len(cols.values))])
+    elif(isinstance(rows, xr.DataArray)):
+        array = np.array([[initial_value for i in range(0, len(rows.values))] for i in range(0,len(cols.values))])
+    else:
+        array = np.array([initial_value for i in range(0,len(cols.values))])
+        
+    coords = {dim: cols.coords[dim] for dim in cols.dims}
+    dims = cols.dims 
+    if(isinstance(rows, xr.DataArray)):
+        coords.update({dim: rows.coords[dim] for dim in rows.dims})
+        dims += rows.dims
+    return xr.DataArray(data=array, coords=coords, dims=dims)  
+    
+def sample_if_true(time, condition, actual_value, initial_value, var_name):
+    """
+    Implements Vensim's SAMPLE IF TRUE function.
+
+    Parameters
+    ----------
+    condition: bool or xarray.DataArray 
+    actual_value: float or xarray.DataArray 
+        Value to return when condition is true.
+    initial_value: float or xarray.DataArray 
+        Value to return when condition is false.
+    var_name: str
+        Represents the SAMPLE IF TRUE function in the whole model.
+
+    Returns
+    -------
+    float or xarray.DataArray
+        Actual_value when condition is true and saved this value
+        in saved_value dictionary.
+        Returns the last saved value when condicion is false.
+        Saved value is initialized with initial_value in the first step of simulation.
+    """
+    global saved_value
+    t = time()
+
+    if(t==0):
+        if(not(isinstance(condition,xr.DataArray))):
+            saved_value[var_name] = initial_value
+        else:
+            saved_value[var_name] = make_da(actual_value, condition, initial_value)
+
+    if isinstance(condition, xr.DataArray):     
+        if condition.all():
+            for i in range(0,len(saved_value[var_name].values)):
+                saved_value[var_name].values[i]=actual_value
+            return saved_value[var_name]
+        elif not condition.any():
+            return saved_value[var_name]
+
+        for i in range(0, len(condition)):
+            if condition.values[i]:
+                saved_value[var_name][i]=actual_value
+        return xr.where(condition, actual_value, saved_value[var_name])
+
+    if condition:
+        saved_value[var_name] = actual_value
+
+    return saved_value[var_name]
 
 def incomplete(*args):
     warnings.warn(
diff --git a/pysd/py_backend/vensim/vensim2py.py b/pysd/py_backend/vensim/vensim2py.py
index adf696fb..102ac6ad 100644
--- a/pysd/py_backend/vensim/vensim2py.py
+++ b/pysd/py_backend/vensim/vensim2py.py
@@ -433,6 +433,17 @@ def parse_units(units_str):
         ],
         "module": "functions"
     },
+    "sample if true": {
+        "name": "sample_if_true",
+        "parameters": [
+            {"name": 'time', "type": 'time'},
+            {"name": 'condition'},
+            {"name": 'val_if_true'},
+            {"name": 'val_if_false'},
+            {"name": 'var_name'}
+        ],
+        "module": "functions"
+    },
     "step": {
         "name": "step",
         "parameters": [
@@ -892,6 +903,10 @@ def visit_call(self, n, vc):
             if self.apply_dim and function_name in vectorial_funcs:
                 arguments += ["dim="+str(tuple(self.apply_dim))]
                 self.apply_dim = set()
+            
+            # add name of variable to sample if true function arguments
+            if(isinstance(functions[function_name],dict) and functions[function_name]['name'] == "sample_if_true"):
+                arguments.append(element['py_name'])
 
             return builder.build_function_call(functions[function_name],
                                                arguments)
diff --git a/tests/integration_test_vensim_pathway.py b/tests/integration_test_vensim_pathway.py
index 5d9e3f54..72f2e4c9 100644
--- a/tests/integration_test_vensim_pathway.py
+++ b/tests/integration_test_vensim_pathway.py
@@ -300,9 +300,7 @@ def test_rounding(self):
         output, canon = runner('test-models/tests/rounding/test_rounding.mdl')
         assert_frames_close(output, canon, rtol=rtol)
 
-    @unittest.skip('working on it #217')
     def test_sample_if_true(self):
-        # issue https://github.com/JamesPHoughton/pysd/issues/217
         from.test_utils import runner, assert_frames_close
         output, canon = runner('test-models/tests/sample_if_true/test_sample_if_true.mdl')
         assert_frames_close(output, canon, rtol=rtol)

From 3c386ff1fe3190c607780c7e71baa288d27e5457 Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Sun, 11 Apr 2021 11:11:56 +0200
Subject: [PATCH 02/17] Added subscript sequence support

---
 pysd/py_backend/vensim/vensim2py.py      | 58 +++++++++++++++++++++++-
 tests/integration_test_vensim_pathway.py |  5 ++
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/pysd/py_backend/vensim/vensim2py.py b/pysd/py_backend/vensim/vensim2py.py
index 102ac6ad..e8c7709a 100644
--- a/pysd/py_backend/vensim/vensim2py.py
+++ b/pysd/py_backend/vensim/vensim2py.py
@@ -256,7 +256,7 @@ def get_equation_components(equation_str, root_path=None):
     component_structure_grammar = _include_common_grammar(r"""
     entry = component / data_definition / test_definition / subscript_definition / lookup_definition
     component = name _ subscriptlist? _ "=" "="? _ expression
-    subscript_definition = name _ ":" _ (imported_subscript / literal_subscript)
+    subscript_definition = name _ ":" _ (imported_subscript / literal_subscript / subscript_sequence)
     data_definition = name _ subscriptlist? _ keyword? _ ":=" _ expression
     lookup_definition = name _ subscriptlist? &"(" _ expression  # uses lookahead assertion to capture whole group
     test_definition = name _ subscriptlist? _ &keyword _ expression
@@ -264,10 +264,14 @@ def get_equation_components(equation_str, root_path=None):
     name = basic_id / escape_group
     literal_subscript = subscript _ ("," _ subscript _)*
     imported_subscript = func _ "(" _ (string _ ","? _)* ")"
+    subscript_sequence = "(" _ sequence_id _ "-" _ sequence_id _ ")"
     subscriptlist = '[' _ subscript _ ("," _ subscript _)* _ ']'
     expression = ~r".*"  # expression could be anything, at this point.
     keyword = ":" _ basic_id _ ":"
 
+    sequence_id = id_common+ numbers+
+    id_common = ~r"[A-Z]"i
+    numbers = ~r"[0-9]"
     subscript = basic_id / escape_group
     func = basic_id
     string = "\'" ( "\\\'" / ~r"[^\']"IU )* "\'"
@@ -313,6 +317,14 @@ def visit_imported_subscript(self, n, vc):
             args_str = vc[4]  # todo: make this less fragile?
             self.subscripts += get_external_data(f_str, args_str, root_path)
 
+        def visit_subscript_sequence(self, n, vc):
+            subscript_start = vc[2].strip()
+            subscript_end = vc[6].strip()
+            substring, start, end = get_subscript_sequence(subscript_start, subscript_end)
+            for i in range(start, end+1):
+                s = substring + str(i)
+                self.subscripts.append(s.strip())
+
         def visit_name(self, n, vc):
             (name,) = vc
             self.real_name = name.strip()
@@ -350,6 +362,50 @@ def get_external_data(func_str, args_str, root_path):
 
     return f(*args, root=root_path).subscript
 
+def get_subscript_sequence(subs_start, subs_end):
+    """
+    With the first and the last subscript of a subscript sequence, 
+    gets the common string of both and the starting and ending
+    number of the subscript sequence
+
+    Parameters
+    ----------
+    subs_start: str
+        Represents the first subscript value in the subscript sequence
+    subs_end: str
+        Represents the last subscript value in the subscript sequence
+    
+    Returns
+    -------
+    common: str
+        Common string of both subscripts
+    num_start: int
+        Sequence start number 
+    num_end: int
+        Sequence end number
+    
+    Examples
+    --------
+    >>> get_subscript_sequence('Layer1', 'Layer5')
+    ('Layer', 1, 5)
+    >>> get_subscript_sequence('sub15', 'sub30')
+    ('sub', 15, 30)
+    """
+    subs_start_l = list(subs_start)
+    subs_end_l = list(subs_end)
+    common = ""
+    for i in range(len(subs_start)):
+        if(subs_start_l[i] == subs_end_l[i] and not(subs_start_l[i].isdigit())):
+            common = common + subs_start_l[i]
+        else: break
+    num_start = subs_start[i:]
+    num_end = subs_end[i:]
+    if(not(num_start.isdigit()) or not(num_end.isdigit()) ): raise ValueError("Format of subscript sequence is not correct\n")
+    num_start = int(num_start)
+    num_end = int(num_end)
+    if(num_start>num_end): raise ValueError("The number of the first subscript must be lower than the second subscript number in a subscript sequence\n")
+
+    return common, num_start, num_end
 
 def parse_units(units_str):
     """
diff --git a/tests/integration_test_vensim_pathway.py b/tests/integration_test_vensim_pathway.py
index 72f2e4c9..fd1d067a 100644
--- a/tests/integration_test_vensim_pathway.py
+++ b/tests/integration_test_vensim_pathway.py
@@ -406,6 +406,11 @@ def test_subscript_selection(self):
         output, canon = runner('test-models/tests/subscript_selection/subscript_selection.mdl')
         assert_frames_close(output, canon, rtol=rtol)
 
+    def test_subscript_sequence(self):
+        from test_utils import runner, assert_frames_close
+        output, canon = runner('test-models/tests/subscript_sequence/test_subscript_sequence.mdl')
+        assert_frames_close(output, canon, rtol=rtol)
+
     def test_subscript_subranges(self):
         from.test_utils import runner, assert_frames_close
         output, canon = runner('test-models/tests/subscript_subranges/test_subscript_subrange.mdl')

From 532a089dd227b79c51c647c373a9049b33e79047 Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Sat, 17 Apr 2021 11:13:48 +0200
Subject: [PATCH 03/17] Updated name of subscript sequence to numeric range,
 and added a grammatical rule

---
 pysd/py_backend/vensim/vensim2py.py      | 39 +++++++++++++-----------
 tests/integration_test_vensim_pathway.py |  4 +--
 2 files changed, 24 insertions(+), 19 deletions(-)

diff --git a/pysd/py_backend/vensim/vensim2py.py b/pysd/py_backend/vensim/vensim2py.py
index e8c7709a..c3ed5dd5 100644
--- a/pysd/py_backend/vensim/vensim2py.py
+++ b/pysd/py_backend/vensim/vensim2py.py
@@ -256,7 +256,7 @@ def get_equation_components(equation_str, root_path=None):
     component_structure_grammar = _include_common_grammar(r"""
     entry = component / data_definition / test_definition / subscript_definition / lookup_definition
     component = name _ subscriptlist? _ "=" "="? _ expression
-    subscript_definition = name _ ":" _ (imported_subscript / literal_subscript / subscript_sequence)
+    subscript_definition = name _ ":" _ (imported_subscript / literal_subscript / numeric_range)
     data_definition = name _ subscriptlist? _ keyword? _ ":=" _ expression
     lookup_definition = name _ subscriptlist? &"(" _ expression  # uses lookahead assertion to capture whole group
     test_definition = name _ subscriptlist? _ &keyword _ expression
@@ -264,7 +264,9 @@ def get_equation_components(equation_str, root_path=None):
     name = basic_id / escape_group
     literal_subscript = subscript _ ("," _ subscript _)*
     imported_subscript = func _ "(" _ (string _ ","? _)* ")"
-    subscript_sequence = "(" _ sequence_id _ "-" _ sequence_id _ ")"
+    numeric_range = _ (range / value) _ ("," _ (range / value) _)*
+    value = _ sequence_id _ 
+    range = "(" _ sequence_id _ "-" _ sequence_id _ ")"
     subscriptlist = '[' _ subscript _ ("," _ subscript _)* _ ']'
     expression = ~r".*"  # expression could be anything, at this point.
     keyword = ":" _ basic_id _ ":"
@@ -317,14 +319,17 @@ def visit_imported_subscript(self, n, vc):
             args_str = vc[4]  # todo: make this less fragile?
             self.subscripts += get_external_data(f_str, args_str, root_path)
 
-        def visit_subscript_sequence(self, n, vc):
-            subscript_start = vc[2].strip()
-            subscript_end = vc[6].strip()
-            substring, start, end = get_subscript_sequence(subscript_start, subscript_end)
+        def visit_range(self, n, vc):
+            subs_start = vc[2].strip()
+            subs_end = vc[6].strip()
+            self.sequence, start, end = get_subscript_number_range(subs_start, subs_end)
             for i in range(start, end+1):
-                s = substring + str(i)
+                s = self.sequence + str(i)
                 self.subscripts.append(s.strip())
 
+        def visit_value(self, n, vc):
+            self.subscripts.append(vc[1])
+
         def visit_name(self, n, vc):
             (name,) = vc
             self.real_name = name.strip()
@@ -362,18 +367,18 @@ def get_external_data(func_str, args_str, root_path):
 
     return f(*args, root=root_path).subscript
 
-def get_subscript_sequence(subs_start, subs_end):
+def get_subscript_number_range(subs_start, subs_end):
     """
-    With the first and the last subscript of a subscript sequence, 
-    gets the common string of both and the starting and ending
-    number of the subscript sequence
+    With the first and the last subscript values of a subscript
+    numeric range, gets the common string of both and the 
+    starting and ending number of the numeric range
 
     Parameters
     ----------
     subs_start: str
-        Represents the first subscript value in the subscript sequence
+        Represents the first subscript value in the numeric range
     subs_end: str
-        Represents the last subscript value in the subscript sequence
+        Represents the last subscript value in the numeric range
     
     Returns
     -------
@@ -386,9 +391,9 @@ def get_subscript_sequence(subs_start, subs_end):
     
     Examples
     --------
-    >>> get_subscript_sequence('Layer1', 'Layer5')
+    >>> get_subscript_number_range('Layer1', 'Layer5')
     ('Layer', 1, 5)
-    >>> get_subscript_sequence('sub15', 'sub30')
+    >>> get_subscript_number_range('sub15', 'sub30')
     ('sub', 15, 30)
     """
     subs_start_l = list(subs_start)
@@ -400,10 +405,10 @@ def get_subscript_sequence(subs_start, subs_end):
         else: break
     num_start = subs_start[i:]
     num_end = subs_end[i:]
-    if(not(num_start.isdigit()) or not(num_end.isdigit()) ): raise ValueError("Format of subscript sequence is not correct\n")
+    if(not(num_start.isdigit()) or not(num_end.isdigit()) ): raise ValueError("Format of subscript numeric range is not correct\n")
     num_start = int(num_start)
     num_end = int(num_end)
-    if(num_start>num_end): raise ValueError("The number of the first subscript must be lower than the second subscript number in a subscript sequence\n")
+    if(num_start>num_end): raise ValueError("The number of the first subscript value must be lower than the second subscript value in a subscript numeric range\n")
 
     return common, num_start, num_end
 
diff --git a/tests/integration_test_vensim_pathway.py b/tests/integration_test_vensim_pathway.py
index fd1d067a..65636807 100644
--- a/tests/integration_test_vensim_pathway.py
+++ b/tests/integration_test_vensim_pathway.py
@@ -406,9 +406,9 @@ def test_subscript_selection(self):
         output, canon = runner('test-models/tests/subscript_selection/subscript_selection.mdl')
         assert_frames_close(output, canon, rtol=rtol)
 
-    def test_subscript_sequence(self):
+    def test_subscript_numeric_range(self):
         from test_utils import runner, assert_frames_close
-        output, canon = runner('test-models/tests/subscript_sequence/test_subscript_sequence.mdl')
+        output, canon = runner('test-models/tests/subscript_numeric_range/test_subscript_numeric_range.mdl')
         assert_frames_close(output, canon, rtol=rtol)
 
     def test_subscript_subranges(self):

From 0baf3dcb98b8cbb3d450f1a8cfc57ec5b2e226ca Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Sat, 17 Apr 2021 11:16:51 +0200
Subject: [PATCH 04/17] Changed the way to split arguments in visit_call of
 expression_grammar

---
 pysd/py_backend/vensim/vensim2py.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/pysd/py_backend/vensim/vensim2py.py b/pysd/py_backend/vensim/vensim2py.py
index c3ed5dd5..65b5907b 100644
--- a/pysd/py_backend/vensim/vensim2py.py
+++ b/pysd/py_backend/vensim/vensim2py.py
@@ -958,7 +958,10 @@ def visit_call(self, n, vc):
             # remove dimensions info (produced by !)
 
             function_name = vc[0].lower()
-            arguments = [e.strip() for e in vc[4].split(",")]
+            arguments = []
+            while len(','.join(arguments)) < len(vc[4]):
+                arguments.append(self.args.pop())
+                arguments = [arguments[-1]] + arguments[:-1]
 
             # add dimensions as last argument
             if self.apply_dim and function_name in vectorial_funcs:

From ce36612b8eaeff8f812a8d3d6f92e8f0d736e649 Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Sat, 17 Apr 2021 11:42:32 +0200
Subject: [PATCH 05/17] Updated import in test_subscript_numeric_range

---
 tests/integration_test_vensim_pathway.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/integration_test_vensim_pathway.py b/tests/integration_test_vensim_pathway.py
index 65636807..479b896a 100644
--- a/tests/integration_test_vensim_pathway.py
+++ b/tests/integration_test_vensim_pathway.py
@@ -407,7 +407,7 @@ def test_subscript_selection(self):
         assert_frames_close(output, canon, rtol=rtol)
 
     def test_subscript_numeric_range(self):
-        from test_utils import runner, assert_frames_close
+        from .test_utils import runner, assert_frames_close
         output, canon = runner('test-models/tests/subscript_numeric_range/test_subscript_numeric_range.mdl')
         assert_frames_close(output, canon, rtol=rtol)
 

From b12f9576626d4602838eded59cc34f859fc5a345 Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Tue, 27 Apr 2021 17:56:15 +0200
Subject: [PATCH 06/17] Update numeric range of subscripts

---
 pysd/py_backend/vensim/vensim2py.py | 46 ++++++++++++++---------------
 1 file changed, 22 insertions(+), 24 deletions(-)

diff --git a/pysd/py_backend/vensim/vensim2py.py b/pysd/py_backend/vensim/vensim2py.py
index 65b5907b..c5b27771 100644
--- a/pysd/py_backend/vensim/vensim2py.py
+++ b/pysd/py_backend/vensim/vensim2py.py
@@ -271,9 +271,7 @@ def get_equation_components(equation_str, root_path=None):
     expression = ~r".*"  # expression could be anything, at this point.
     keyword = ":" _ basic_id _ ":"
 
-    sequence_id = id_common+ numbers+
-    id_common = ~r"[A-Z]"i
-    numbers = ~r"[0-9]"
+    sequence_id = _ basic_id _
     subscript = basic_id / escape_group
     func = basic_id
     string = "\'" ( "\\\'" / ~r"[^\']"IU )* "\'"
@@ -322,13 +320,13 @@ def visit_imported_subscript(self, n, vc):
         def visit_range(self, n, vc):
             subs_start = vc[2].strip()
             subs_end = vc[6].strip()
-            self.sequence, start, end = get_subscript_number_range(subs_start, subs_end)
+            self.sequence, start, end = get_subscript_numeric_range(subs_start, subs_end)
             for i in range(start, end+1):
                 s = self.sequence + str(i)
                 self.subscripts.append(s.strip())
 
         def visit_value(self, n, vc):
-            self.subscripts.append(vc[1])
+            self.subscripts.append(vc[1].strip())
 
         def visit_name(self, n, vc):
             (name,) = vc
@@ -367,10 +365,10 @@ def get_external_data(func_str, args_str, root_path):
 
     return f(*args, root=root_path).subscript
 
-def get_subscript_number_range(subs_start, subs_end):
+def get_subscript_numeric_range(subs_start, subs_end):
     """
     With the first and the last subscript values of a subscript
-    numeric range, gets the common string of both and the 
+    numeric range, gets the common prefix of both and the 
     starting and ending number of the numeric range
 
     Parameters
@@ -382,8 +380,8 @@ def get_subscript_number_range(subs_start, subs_end):
     
     Returns
     -------
-    common: str
-        Common string of both subscripts
+    prefix: str
+        Common prefix of both subscripts
     num_start: int
         Sequence start number 
     num_end: int
@@ -396,21 +394,21 @@ def get_subscript_number_range(subs_start, subs_end):
     >>> get_subscript_number_range('sub15', 'sub30')
     ('sub', 15, 30)
     """
-    subs_start_l = list(subs_start)
-    subs_end_l = list(subs_end)
-    common = ""
-    for i in range(len(subs_start)):
-        if(subs_start_l[i] == subs_end_l[i] and not(subs_start_l[i].isdigit())):
-            common = common + subs_start_l[i]
-        else: break
-    num_start = subs_start[i:]
-    num_end = subs_end[i:]
-    if(not(num_start.isdigit()) or not(num_end.isdigit()) ): raise ValueError("Format of subscript numeric range is not correct\n")
-    num_start = int(num_start)
-    num_end = int(num_end)
-    if(num_start>num_end): raise ValueError("The number of the first subscript value must be lower than the second subscript value in a subscript numeric range\n")
-
-    return common, num_start, num_end
+    if(subs_start == subs_end): raise ValueError('Only different subscripts are valid in a numeric range')
+
+    subs_start = re.findall('\d+|\D+', subs_start)
+    subs_end = re.findall('\d+|\D+', subs_end)
+    prefix_start = ''.join(subs_start[:-1])
+    prefix_end = ''.join(subs_start[:-1])
+    num_start = int(subs_start[-1])
+    num_end = int(subs_end[-1])
+
+    if(not(prefix_start) or not(prefix_end)): raise ValueError('A numeric range must contain at least one letter')
+    if(num_start>num_end): raise ValueError('The number of the first subscript value must be lower than the second subscript value in a subscript numeric range\n')
+    if(prefix_start != prefix_end or subs_start[0].isdigit() or subs_end[0].isdigit()): raise ValueError('Only matching names ending in numbers are valid')
+
+    return prefix_start, num_start, num_end
+
 
 def parse_units(units_str):
     """

From 2c1ce8440cda7343e7539cd6fb7c3069bd70b680 Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Wed, 28 Apr 2021 19:08:38 +0200
Subject: [PATCH 07/17] A variable that is not an attribute was renamed

---
 pysd/py_backend/vensim/vensim2py.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pysd/py_backend/vensim/vensim2py.py b/pysd/py_backend/vensim/vensim2py.py
index c5b27771..8f59f822 100644
--- a/pysd/py_backend/vensim/vensim2py.py
+++ b/pysd/py_backend/vensim/vensim2py.py
@@ -320,9 +320,9 @@ def visit_imported_subscript(self, n, vc):
         def visit_range(self, n, vc):
             subs_start = vc[2].strip()
             subs_end = vc[6].strip()
-            self.sequence, start, end = get_subscript_numeric_range(subs_start, subs_end)
+            prefix, start, end = get_subscript_numeric_range(subs_start, subs_end)
             for i in range(start, end+1):
-                s = self.sequence + str(i)
+                s = prefix + str(i)
                 self.subscripts.append(s.strip())
 
         def visit_value(self, n, vc):

From 8b2a16ead394bfe3fd6054482b535675645bd4e5 Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Wed, 5 May 2021 17:57:25 +0200
Subject: [PATCH 08/17] Update test-models repository

---
 tests/test-models | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/test-models b/tests/test-models
index a132c9a3..d2a3c918 160000
--- a/tests/test-models
+++ b/tests/test-models
@@ -1 +1 @@
-Subproject commit a132c9a3fcaf0950ba5fd97ed59f9a4aa9e46294
+Subproject commit d2a3c9183a351d5a081bcab80ed9b8dcda396c2e

From b3afbd951c71b95c30e4ae1f586abe6e0f34d001 Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Wed, 5 May 2021 17:58:28 +0200
Subject: [PATCH 09/17] Updated prefix end of subscript numeric sequence

---
 pysd/py_backend/vensim/vensim2py.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pysd/py_backend/vensim/vensim2py.py b/pysd/py_backend/vensim/vensim2py.py
index 8f59f822..0ba93aa2 100644
--- a/pysd/py_backend/vensim/vensim2py.py
+++ b/pysd/py_backend/vensim/vensim2py.py
@@ -399,7 +399,7 @@ def get_subscript_numeric_range(subs_start, subs_end):
     subs_start = re.findall('\d+|\D+', subs_start)
     subs_end = re.findall('\d+|\D+', subs_end)
     prefix_start = ''.join(subs_start[:-1])
-    prefix_end = ''.join(subs_start[:-1])
+    prefix_end = ''.join(subs_end[:-1])
     num_start = int(subs_start[-1])
     num_end = int(subs_end[-1])
 

From 601e2f757acbd9d609807707c23371512dc834e6 Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Thu, 6 May 2021 16:53:07 +0200
Subject: [PATCH 10/17] The conflict merged and tests bugs fixed

---
 pysd/py_backend/vensim/vensim2py.py | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/pysd/py_backend/vensim/vensim2py.py b/pysd/py_backend/vensim/vensim2py.py
index 5c89c1f6..634b84db 100644
--- a/pysd/py_backend/vensim/vensim2py.py
+++ b/pysd/py_backend/vensim/vensim2py.py
@@ -276,7 +276,7 @@ def get_equation_components(equation_str, root_path=None):
     name = basic_id / escape_group
 
     literal_subscript = subscript _ ("," _ subscript _)*
-    imported_subscript = func _ "(" _ (string _ ","? _)* ")"
+    imported_subscript = imp_subs_func _ "(" _ (string _ ","? _)* ")"
     numeric_range = _ (range / value) _ ("," _ (range / value) _)*
     value = _ sequence_id _ 
     range = "(" _ sequence_id _ "-" _ sequence_id _ ")"
@@ -594,10 +594,7 @@ def parse_units(units_str):
                       "original_name": "INVERT MATRIX"},
     "get time value": {"name": "not_implemented_function",
                       "module": "functions",
-                      "original_name": "GET TIME VALUE"},
-    "sample if true": {"name": "not_implemented_function",
-                      "module": "functions",
-                      "original_name": "SAMPLE IF TRUE"}
+                      "original_name": "GET TIME VALUE"}
 }
 
 # list of fuctions that accept a dimension to apply over

From 0e24ac723dbdb1c91bd33b540364ea81180402df Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Sat, 8 May 2021 12:17:43 +0200
Subject: [PATCH 11/17] Updated with new version of PySD

---
 pysd/py_backend/vensim/vensim2py.py | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/pysd/py_backend/vensim/vensim2py.py b/pysd/py_backend/vensim/vensim2py.py
index 634b84db..777ab50a 100644
--- a/pysd/py_backend/vensim/vensim2py.py
+++ b/pysd/py_backend/vensim/vensim2py.py
@@ -379,18 +379,6 @@ def visit__(self, n, vc):
             'kind': parse_object.kind,
             'keyword': parse_object.keyword}
 
-
-def get_external_data(func_str, args_str, root_path):
-    """
-    Gets the subscripts from external files calling the class external.ExtSubscript
-    """
-    # The py model file must be recompiled if external file subscripts change. This could be avoided
-    # if we switch to function-defined subscript values instead of hard-coding them.
-    f = subscript_functions[func_str.lower()]
-    args = [x.strip().strip("\'") for x in args_str.split(',')]  # todo: make this less fragile?
-
-    return f(*args, root=root_path).subscript
-
 def get_subscript_numeric_range(subs_start, subs_end):
     """
     With the first and the last subscript values of a subscript

From 5b68e6251fa7eaddbb69a678f42c57209280b555 Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Mon, 10 May 2021 16:34:02 +0200
Subject: [PATCH 12/17] Implement sample if true functionality as a Stateful
 object

---
 pysd/py_backend/builder.py          | 111 ++++++++++++++++++++++
 pysd/py_backend/functions.py        | 142 +++++++++++-----------------
 pysd/py_backend/vensim/vensim2py.py |  26 ++---
 3 files changed, 176 insertions(+), 103 deletions(-)

diff --git a/pysd/py_backend/builder.py b/pysd/py_backend/builder.py
index 89f69daf..7c4e8fc9 100644
--- a/pysd/py_backend/builder.py
+++ b/pysd/py_backend/builder.py
@@ -565,6 +565,117 @@ def add_n_delay(identifier, delay_input, delay_time, initial_value, order,
     return "%s()" % stateful['py_name'], new_structure
 
 
+def add_sample_if_true(identifier, condition, actual_value, initial_value,
+                subs, subscript_dict):
+    """
+    Creates code to instantiate a stateful 'SampleIfTrue' object,
+    and provides reference to that object's output.
+
+    Parameters
+    ----------
+    identifier: basestring
+        the python-safe name of the stock
+
+    condition: <string>
+        Reference to another model element that is the condition to the 
+        'sample if true' function
+
+    actual_value: <string>
+        Can be a number (in string format) or a reference to another model
+        element which is calculated throughout the simulation at runtime.
+
+    initial_value: <string>
+        This is used to initialize the state of the sample if true function.
+
+    subs: list of strings
+        List of strings of subscript indices that correspond to the
+        list of expressions, and collectively define the shape of the output
+
+    subscript_dict: dictionary
+        Dictionary describing the possible dimensions of the stock's subscripts
+
+    Returns
+    -------
+    reference: basestring
+        reference to the sample if true object `__call__` method, 
+        which will return the output of the sample if true process
+
+    new_structure: list
+        list of element construction dictionaries for the builder to assemble
+
+    """
+    import_modules['functions'].add("SampleIfTrue")
+
+    new_structure = []
+
+    if len(subs) == 0:
+        stateful_py_expr = 'SampleIfTrue(lambda: %s, lambda: %s,'\
+                           'lambda: %s)' % (condition, actual_value, initial_value)
+    
+    else:
+        stateful_py_expr = 'SampleIfTrue(lambda: _condition_%s(),'\
+                           'lambda: _input_%s(), lambda: _init_%s(),)' % (
+                               identifier, identifier, identifier)
+        # following elements not specified in the model file, but must exist
+        # create the sample if true initialization element
+        new_structure.append({
+            'py_name': '_init_%s' % identifier,
+            'real_name': 'Implicit',
+            'kind': 'setup',  # not specified in the model file, but must exist
+            'py_expr': initial_value,
+            'subs': subs,
+            'doc': 'Provides initial value for %s function' % identifier,
+            'unit': 'See docs for %s' % identifier,
+            'lims': 'None',
+            'eqn': 'None',
+            'arguments': ''
+        })
+
+        new_structure.append({
+            'py_name': '_condition_%s' % identifier,
+            'real_name': 'Implicit',
+            'kind': 'component',
+            'doc': 'Provides condition for %s function' % identifier,
+            'subs': subs,
+            'unit': 'See docs for %s' % identifier,
+            'lims': 'None',
+            'eqn': 'None',
+            'py_expr': condition,
+            'arguments': ''
+        })
+
+        new_structure.append({
+            'py_name': '_input_%s' % identifier,
+            'real_name': 'Implicit',
+            'kind': 'component',
+            'doc': 'Provides input for %s function' % identifier,
+            'subs': subs,
+            'unit': 'See docs for %s' % identifier,
+            'lims': 'None',
+            'eqn': 'None',
+            'py_expr': actual_value,
+            'arguments': ''
+        })
+
+    # describe the stateful object
+    stateful = {
+        'py_name': '_sample_if_true_%s' % identifier,
+        'real_name': 'Sample if true of %s' % identifier,
+        'doc': 'Initial value: %s \n  Input: %s \n Condition: %s' % (
+            initial_value, actual_value, condition),
+        'py_expr': stateful_py_expr,
+        'unit': 'None',
+        'lims': 'None',
+        'eqn': 'None',
+        'subs': '',
+        'kind': 'stateful',
+        'arguments': ''
+    }
+    new_structure.append(stateful)
+
+    return "%s()" % stateful['py_name'], new_structure
+
+
 def add_n_smooth(identifier, smooth_input, smooth_time, initial_value, order,
                  subs, subscript_dict):
     """
diff --git a/pysd/py_backend/functions.py b/pysd/py_backend/functions.py
index 3e272814..9f881e9f 100644
--- a/pysd/py_backend/functions.py
+++ b/pysd/py_backend/functions.py
@@ -170,6 +170,33 @@ def ddt(self):
             inflows[0] = self.input_func()
         return inflows - outflows
 
+class SampleIfTrue(Stateful):
+    def __init__(self, condition, actual_value, initial_value):
+        """
+
+        Parameters
+        ----------
+        condition: function
+        actual_value: function
+        initial_value: function
+        """
+        super().__init__()
+        self.condition = condition
+        self.actual_value = actual_value
+        self.initial_value = initial_value
+    
+    def initialize(self):
+        self.state = self.initial_value()
+        if isinstance(self.state, xr.DataArray):
+            self.shape_info = {'dims': self.state.dims,
+                               'coords': self.state.coords}
+    
+    def __call__(self):
+        self.state = sample_if_true(self.condition(), self.actual_value(), self.state)
+        return self.state
+    
+    def ddt(self):
+        return 0
 
 class Smooth(Stateful):
     def __init__(self, smooth_input, smooth_time, initial_value, order):
@@ -1091,6 +1118,34 @@ def if_then_else(condition, val_if_true, val_if_false):
     return val_if_true() if condition else val_if_false()
 
 
+def sample_if_true(condition, actual_value, saved_value):
+    """
+    Implements Vensim's SAMPLE IF TRUE function.
+
+    Parameters
+    ----------
+    condition: bool or xarray.DataArray of bools
+    actual_value: int, float or xarray.DataArray
+        Value to return when condition is true.
+    saved_value: int, float or xarray.DataArray
+        Value to return when condition is false.
+
+    Returns
+    -------
+    The value depending on the condition.
+
+    """
+    if isinstance(condition, xr.DataArray):
+        if condition.all():
+            return actual_value
+        elif not condition.any():
+            return saved_value
+
+        return xr.where(condition, actual_value, saved_value)
+
+    return actual_value if condition else saved_value
+
+
 def xidz(numerator, denominator, value_if_denom_is_zero):
     """
     Implements Vensim's XIDZ function.
@@ -1202,93 +1257,6 @@ def random_uniform(m, x, s):
 
     return np.random.uniform(m, x)
 
-# dictionary to store the values from SAMPLE IF TRUE function
-saved_value = {}
-
-def make_da(rows, cols, initial_value):
-    """
-    Returns a DataArray with the coordinates
-    of the rows and cols.
-    DataArray values are initialized with the initial_value.
-    It is used in SAMPLE IF TRUE function, to create the proper dimension saved value.
-    
-    Parameters
-    ----------
-    rows: float or xarray.DataArray    
-        Represents the row dimension of the new DataArray
-    cols: xarray.DataArray 
-        Represents the col dimension of the new DataArray
-    initial_value: float or xarray.DataArray 
-        Include the values to initialize the new DataArray
-
-    Returns
-    -------
-    A new DataArray with proper rows and cols coordinates,
-    initialized with initial_value
-    
-    """
-    if(isinstance(initial_value,xr.DataArray)):
-        array = np.array([[initial_value.data[e] for i in range(0, len(rows.values))] for e in range(0,len(cols.values))])
-    elif(isinstance(rows, xr.DataArray)):
-        array = np.array([[initial_value for i in range(0, len(rows.values))] for i in range(0,len(cols.values))])
-    else:
-        array = np.array([initial_value for i in range(0,len(cols.values))])
-        
-    coords = {dim: cols.coords[dim] for dim in cols.dims}
-    dims = cols.dims 
-    if(isinstance(rows, xr.DataArray)):
-        coords.update({dim: rows.coords[dim] for dim in rows.dims})
-        dims += rows.dims
-    return xr.DataArray(data=array, coords=coords, dims=dims)  
-    
-def sample_if_true(time, condition, actual_value, initial_value, var_name):
-    """
-    Implements Vensim's SAMPLE IF TRUE function.
-
-    Parameters
-    ----------
-    condition: bool or xarray.DataArray 
-    actual_value: float or xarray.DataArray 
-        Value to return when condition is true.
-    initial_value: float or xarray.DataArray 
-        Value to return when condition is false.
-    var_name: str
-        Represents the SAMPLE IF TRUE function in the whole model.
-
-    Returns
-    -------
-    float or xarray.DataArray
-        Actual_value when condition is true and saved this value
-        in saved_value dictionary.
-        Returns the last saved value when condicion is false.
-        Saved value is initialized with initial_value in the first step of simulation.
-    """
-    global saved_value
-    t = time()
-
-    if(t==0):
-        if(not(isinstance(condition,xr.DataArray))):
-            saved_value[var_name] = initial_value
-        else:
-            saved_value[var_name] = make_da(actual_value, condition, initial_value)
-
-    if isinstance(condition, xr.DataArray):     
-        if condition.all():
-            for i in range(0,len(saved_value[var_name].values)):
-                saved_value[var_name].values[i]=actual_value
-            return saved_value[var_name]
-        elif not condition.any():
-            return saved_value[var_name]
-
-        for i in range(0, len(condition)):
-            if condition.values[i]:
-                saved_value[var_name][i]=actual_value
-        return xr.where(condition, actual_value, saved_value[var_name])
-
-    if condition:
-        saved_value[var_name] = actual_value
-
-    return saved_value[var_name]
 
 def incomplete(*args):
     warnings.warn(
diff --git a/pysd/py_backend/vensim/vensim2py.py b/pysd/py_backend/vensim/vensim2py.py
index 777ab50a..793c0611 100644
--- a/pysd/py_backend/vensim/vensim2py.py
+++ b/pysd/py_backend/vensim/vensim2py.py
@@ -505,17 +505,6 @@ def parse_units(units_str):
         ],
         "module": "functions"
     },
-    "sample if true": {
-        "name": "sample_if_true",
-        "parameters": [
-            {"name": 'time', "type": 'time'},
-            {"name": 'condition'},
-            {"name": 'val_if_true'},
-            {"name": 'val_if_false'},
-            {"name": 'var_name'}
-        ],
-        "module": "functions"
-    },
     "step": {
         "name": "step",
         "parameters": [
@@ -691,7 +680,16 @@ def parse_units(units_str):
         subs=element['subs'],
         subscript_dict=subscript_dict
     ),
-
+    
+    "sample if true": lambda element, subscript_dict, args: builder.add_sample_if_true(
+        identifier=element['py_name'],
+        condition=args[0],
+        actual_value=args[1],
+        initial_value=args[2],
+        subs=element['subs'],
+        subscript_dict=subscript_dict
+    ),
+    
     "smooth": lambda element, subscript_dict, args: builder.add_n_smooth(
         identifier=element['py_name'],
         smooth_input=args[0],
@@ -970,10 +968,6 @@ def visit_call(self, n, vc):
             if self.apply_dim and function_name in vectorial_funcs:
                 arguments += ["dim="+str(tuple(self.apply_dim))]
                 self.apply_dim = set()
-            
-            # add name of variable to sample if true function arguments
-            if(isinstance(functions[function_name],dict) and functions[function_name]['name'] == "sample_if_true"):
-                arguments.append(element['py_name'])
 
             return builder.build_function_call(functions[function_name],
                                                arguments)

From c095ee1564834d7746c4fc1f815e16a3d2a9cd32 Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Mon, 10 May 2021 17:11:45 +0200
Subject: [PATCH 13/17] Add more information in the errors of
 visit_numeric_range and removed the function get_subscript_numeric_range and
 the code has been added to the visitor

---
 pysd/py_backend/vensim/vensim2py.py | 63 ++++++++---------------------
 1 file changed, 17 insertions(+), 46 deletions(-)

diff --git a/pysd/py_backend/vensim/vensim2py.py b/pysd/py_backend/vensim/vensim2py.py
index 793c0611..22d9874a 100644
--- a/pysd/py_backend/vensim/vensim2py.py
+++ b/pysd/py_backend/vensim/vensim2py.py
@@ -335,9 +335,23 @@ def visit_imported_subscript(self, n, vc):
         def visit_range(self, n, vc):
             subs_start = vc[2].strip()
             subs_end = vc[6].strip()
-            prefix, start, end = get_subscript_numeric_range(subs_start, subs_end)
-            for i in range(start, end+1):
-                s = prefix + str(i)
+            if(subs_start == subs_end): raise ValueError('Only different subscripts are valid in a numeric range, error in expression:\n\t %s\n' % (equation_str))
+            
+            # get the common prefix and the starting and 
+            # ending number of the numeric range
+            subs_start = re.findall('\d+|\D+', subs_start)
+            subs_end = re.findall('\d+|\D+', subs_end)
+            prefix_start = ''.join(subs_start[:-1])
+            prefix_end = ''.join(subs_end[:-1])
+            num_start = int(subs_start[-1])
+            num_end = int(subs_end[-1])
+
+            if(not(prefix_start) or not(prefix_end)): raise ValueError('A numeric range must contain at least one letter, error in expression:\n\t %s\n' % (equation_str))
+            if(num_start>num_end): raise ValueError('The number of the first subscript value must be lower than the second subscript value in a subscript numeric range, error in expression:\n\t %s\n'% (equation_str))
+            if(prefix_start != prefix_end or subs_start[0].isdigit() or subs_end[0].isdigit()): raise ValueError('Only matching names ending in numbers are valid, error in expression:\n\t %s\n'% (equation_str))
+
+            for i in range(num_start, num_end+1):
+                s = prefix_start + str(i)
                 self.subscripts.append(s.strip())
 
         def visit_value(self, n, vc):
@@ -379,49 +393,6 @@ def visit__(self, n, vc):
             'kind': parse_object.kind,
             'keyword': parse_object.keyword}
 
-def get_subscript_numeric_range(subs_start, subs_end):
-    """
-    With the first and the last subscript values of a subscript
-    numeric range, gets the common prefix of both and the 
-    starting and ending number of the numeric range
-
-    Parameters
-    ----------
-    subs_start: str
-        Represents the first subscript value in the numeric range
-    subs_end: str
-        Represents the last subscript value in the numeric range
-    
-    Returns
-    -------
-    prefix: str
-        Common prefix of both subscripts
-    num_start: int
-        Sequence start number 
-    num_end: int
-        Sequence end number
-    
-    Examples
-    --------
-    >>> get_subscript_number_range('Layer1', 'Layer5')
-    ('Layer', 1, 5)
-    >>> get_subscript_number_range('sub15', 'sub30')
-    ('sub', 15, 30)
-    """
-    if(subs_start == subs_end): raise ValueError('Only different subscripts are valid in a numeric range')
-
-    subs_start = re.findall('\d+|\D+', subs_start)
-    subs_end = re.findall('\d+|\D+', subs_end)
-    prefix_start = ''.join(subs_start[:-1])
-    prefix_end = ''.join(subs_end[:-1])
-    num_start = int(subs_start[-1])
-    num_end = int(subs_end[-1])
-
-    if(not(prefix_start) or not(prefix_end)): raise ValueError('A numeric range must contain at least one letter')
-    if(num_start>num_end): raise ValueError('The number of the first subscript value must be lower than the second subscript value in a subscript numeric range\n')
-    if(prefix_start != prefix_end or subs_start[0].isdigit() or subs_end[0].isdigit()): raise ValueError('Only matching names ending in numbers are valid')
-
-    return prefix_start, num_start, num_end
 
 def parse_units(units_str):
     """

From ee9db93adcf35bb91f8dd076987a185d964043d8 Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Mon, 10 May 2021 18:10:19 +0200
Subject: [PATCH 14/17] Updated version of pysd

---
 pysd/_version.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pysd/_version.py b/pysd/_version.py
index c1afe526..17949574 100644
--- a/pysd/_version.py
+++ b/pysd/_version.py
@@ -1,2 +1,2 @@
-__version__ = "1.2.0"
+__version__ = "1.3.0"
 

From 35243c856194c626a0da59fe066f69fda654685c Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Mon, 10 May 2021 18:16:05 +0200
Subject: [PATCH 15/17] Updated sample if true class, deleted sample_if_true
 function

---
 pysd/py_backend/functions.py | 30 +-----------------------------
 1 file changed, 1 insertion(+), 29 deletions(-)

diff --git a/pysd/py_backend/functions.py b/pysd/py_backend/functions.py
index 9f881e9f..3736f646 100644
--- a/pysd/py_backend/functions.py
+++ b/pysd/py_backend/functions.py
@@ -192,7 +192,7 @@ def initialize(self):
                                'coords': self.state.coords}
     
     def __call__(self):
-        self.state = sample_if_true(self.condition(), self.actual_value(), self.state)
+        self.state = if_then_else(self.condition(), self.actual_value, lambda: self.state)
         return self.state
     
     def ddt(self):
@@ -1118,34 +1118,6 @@ def if_then_else(condition, val_if_true, val_if_false):
     return val_if_true() if condition else val_if_false()
 
 
-def sample_if_true(condition, actual_value, saved_value):
-    """
-    Implements Vensim's SAMPLE IF TRUE function.
-
-    Parameters
-    ----------
-    condition: bool or xarray.DataArray of bools
-    actual_value: int, float or xarray.DataArray
-        Value to return when condition is true.
-    saved_value: int, float or xarray.DataArray
-        Value to return when condition is false.
-
-    Returns
-    -------
-    The value depending on the condition.
-
-    """
-    if isinstance(condition, xr.DataArray):
-        if condition.all():
-            return actual_value
-        elif not condition.any():
-            return saved_value
-
-        return xr.where(condition, actual_value, saved_value)
-
-    return actual_value if condition else saved_value
-
-
 def xidz(numerator, denominator, value_if_denom_is_zero):
     """
     Implements Vensim's XIDZ function.

From 494e57198a9ec84e1dc94b43177dd4d1d4b41543 Mon Sep 17 00:00:00 2001
From: Maria <maria.robles.blanco@alumnos.uva.es>
Date: Mon, 10 May 2021 18:23:02 +0200
Subject: [PATCH 16/17] SampleIfTrue added

---
 docs/development/supported_vensim_functions.rst | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/docs/development/supported_vensim_functions.rst b/docs/development/supported_vensim_functions.rst
index 37a14fb3..6ec979b6 100644
--- a/docs/development/supported_vensim_functions.rst
+++ b/docs/development/supported_vensim_functions.rst
@@ -69,6 +69,8 @@
 +------------------------------+------------------------------+
 |           DELAY N            |        functions.Delay       |
 +------------------------------+------------------------------+
+|        SAMPLE IF TRUE        |    functions.SampleIfTrue    |
++------------------------------+------------------------------+
 |           SMOOTH3I           |        functions.Smooth      |
 +------------------------------+------------------------------+
 |           SMOOTH3            |        functions.Smooth      |

From 10338cae89e5958aedb9c5e61610997599b86c0f Mon Sep 17 00:00:00 2001
From: Eneko Martin Martinez
 <61285767+enekomartinmartinez@users.noreply.github.com>
Date: Tue, 11 May 2021 09:45:13 +0200
Subject: [PATCH 17/17] Add update method to SampleIfTrue

Add update method to SampleIfTrue with a pass, so when trying to update SampleIfTrue nothing will be done.
Improves reliability and speed.
---
 pysd/py_backend/functions.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/pysd/py_backend/functions.py b/pysd/py_backend/functions.py
index 3736f646..14bafbeb 100644
--- a/pysd/py_backend/functions.py
+++ b/pysd/py_backend/functions.py
@@ -198,6 +198,10 @@ def __call__(self):
     def ddt(self):
         return 0
 
+    def update(self, state):
+        # this doesn't change once it's set up.
+        pass
+
 class Smooth(Stateful):
     def __init__(self, smooth_input, smooth_time, initial_value, order):
         super().__init__()