--- /dev/null
+"""
+Copyright 2008, 2009 Free Software Foundation, Inc.
+This file is part of GNU Radio
+
+GNU Radio Companion is free software; you can redistribute it and/or
+modify it under the terms of the GNU General Public License
+as published by the Free Software Foundation; either version 2
+of the License, or (at your option) any later version.
+
+GNU Radio Companion is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
+"""
+
+import string
+VAR_CHARS = string.letters + string.digits + '_'
+
+class graph(object):
+ """
+ Simple graph structure held in a dictionary.
+ """
+
+ def __init__(self): self._graph = dict()
+
+ def __str__(self): return str(self._graph)
+
+ def add_node(self, node_key):
+ if self._graph.has_key(node_key): return
+ self._graph[node_key] = set()
+
+ def remove_node(self, node_key):
+ if not self._graph.has_key(node_key): return
+ for edges in self._graph.values():
+ if node_key in edges: edges.remove(node_key)
+ self._graph.pop(node_key)
+
+ def add_edge(self, src_node_key, dest_node_key):
+ self._graph[src_node_key].add(dest_node_key)
+
+ def remove_edge(self, src_node_key, dest_node_key):
+ self._graph[src_node_key].remove(dest_node_key)
+
+ def get_nodes(self): return self._graph.keys()
+
+ def get_edges(self, node_key): return self._graph[node_key]
+
+def expr_split(expr):
+ """
+ Split up an expression by non alphanumeric characters, including underscore.
+ Leave strings in-tact.
+ #TODO ignore escaped quotes, use raw strings.
+ @param expr an expression string
+ @return a list of string tokens that form expr
+ """
+ toks = list()
+ tok = ''
+ quote = ''
+ for char in expr:
+ if quote or char in VAR_CHARS:
+ if char == quote: quote = ''
+ tok += char
+ elif char in ("'", '"'):
+ toks.append(tok)
+ tok = char
+ quote = char
+ else:
+ toks.append(tok)
+ toks.append(char)
+ tok = ''
+ toks.append(tok)
+ return filter(lambda t: t, toks)
+
+def expr_replace(expr, replace_dict):
+ """
+ Search for vars in the expression and add the prepend.
+ @param expr an expression string
+ @param replace_dict a dict of find:replace
+ @return a new expression with the prepend
+ """
+ expr_splits = expr_split(expr)
+ for i, es in enumerate(expr_splits):
+ if es in replace_dict.keys():
+ expr_splits[i] = replace_dict[es]
+ return ''.join(expr_splits)
+
+def get_variable_dependencies(expr, vars):
+ """
+ Return a set of variables used in this expression.
+ @param expr an expression string
+ @param vars a list of variable names
+ @return a subset of vars used in the expression
+ """
+ expr_toks = expr_split(expr)
+ return set(filter(lambda v: v in expr_toks, vars))
+
+def get_graph(exprs):
+ """
+ Get a graph representing the variable dependencies
+ @param exprs a mapping of variable name to expression
+ @return a graph of variable deps
+ """
+ vars = exprs.keys()
+ #get dependencies for each expression, load into graph
+ var_graph = graph()
+ for var in vars: var_graph.add_node(var)
+ for var, expr in exprs.iteritems():
+ for dep in get_variable_dependencies(expr, vars):
+ if dep != var: var_graph.add_edge(dep, var)
+ return var_graph
+
+def sort_variables(exprs):
+ """
+ Get a list of variables in order of dependencies.
+ @param exprs a mapping of variable name to expression
+ @return a list of variable names
+ @throws AssertionError circular dependencies
+ """
+ var_graph = get_graph(exprs)
+ sorted_vars = list()
+ #determine dependency order
+ while var_graph.get_nodes():
+ #get a list of nodes with no edges
+ indep_vars = filter(lambda var: not var_graph.get_edges(var), var_graph.get_nodes())
+ assert indep_vars
+ #add the indep vars to the end of the list
+ sorted_vars.extend(sorted(indep_vars))
+ #remove each edge-less node from the graph
+ for var in indep_vars: var_graph.remove_node(var)
+ return reversed(sorted_vars)
+
+def sort_objects(objects, get_id, get_expr):
+ """
+ Sort a list of objects according to their expressions.
+ @param objects the list of objects to sort
+ @param get_id the function to extract an id from the object
+ @param get_expr the function to extract an expression from the object
+ @return a list of sorted objects
+ """
+ id2obj = dict([(get_id(obj), obj) for obj in objects])
+ #map obj id to expression code
+ id2expr = dict([(get_id(obj), get_expr(obj)) for obj in objects])
+ #sort according to dependency
+ sorted_ids = sort_variables(id2expr)
+ #return list of sorted objects
+ return [id2obj[id] for id in sorted_ids]
+
+if __name__ == '__main__':
+ for i in sort_variables({'x':'1', 'y':'x+1', 'a':'x+y', 'b':'y+1', 'c':'a+b+x+y'}): print i
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