188 def ast_sym(ast, env):  argument
189     if ast in env:
190         return str(env[ast])
193 def ast_sym_int(ast, env):  argument
194     if ast in env:
195         v = env[ast]
202 def ast_expr(ast, env, edt):  argument
203     if ast[0] == "not":
204         return not ast_expr(ast[1], env, edt)
205     elif ast[0] == "or":
206         return ast_expr(ast[1], env, edt) or ast_expr(ast[2], env, edt)
207     elif ast[0] == "and":
208         return ast_expr(ast[1], env, edt) and ast_expr(ast[2], env, edt)
209     elif ast[0] == "==":
210         return ast_sym(ast[1], env) == ast[2]
211     elif ast[0] == "!=":
212         return ast_sym(ast[1], env) != ast[2]
213     elif ast[0] == ">":
214         return ast_sym_int(ast[1], env) > int(ast[2])
215     elif ast[0] == "<":
216         return ast_sym_int(ast[1], env) < int(ast[2])
217     elif ast[0] == ">=":
218         return ast_sym_int(ast[1], env) >= int(ast[2])
219     elif ast[0] == "<=":
220         return ast_sym_int(ast[1], env) <= int(ast[2])
221     elif ast[0] == "in":
222         return ast_sym(ast[1], env) in ast[2]
223     elif ast[0] == "exists":
224         return bool(ast_sym(ast[1], env))
225     elif ast[0] == ":":
226         return bool(re.match(ast[2], ast_sym(ast[1], env)))
227     elif ast[0] == "dt_compat_enabled":
228         compat = ast[1][0]
233     elif ast[0] == "dt_alias_exists":
234         alias = ast[1][0]
239     elif ast[0] == "dt_enabled_alias_with_parent_compat":
244         alias = ast[1][0]
245         compat = ast[1][1]
254     elif ast[0] == "dt_label_with_parent_compat_enabled":
255         compat = ast[1][1]
256         label = ast[1][0]
264     elif ast[0] == "dt_chosen_enabled":
265         chosen = ast[1][0]
270     elif ast[0] == "dt_nodelabel_enabled":
271         label = ast[1][0]
276     elif ast[0] == "dt_node_prop_enabled":
277         label = ast[1][0]
279         prop = ast[1][1]
295         ast = parser.parse(expr_text)
299     return ast_expr(ast, env, edt)