如何检查符号eq1是否等于Matlab中的符号eq2：
syms a x y
eq1 = a*(x+y)
eq2 = a*x + a*y
答案 0 :(得分：4)
您可以在差异上使用simplify，然后logical来测试它是否等于0：
eqAreEqual = logical(simplify(eq1-eq2) == 0);
您还可以在每个simplify上使用isequal进行比较：
eqAreEqual = isequal(simplify(eq1), simplify(eq2));
例如：
>> syms a x y
>> eq1 = a*(x+y);
>> eq2 = a*x + a*y;
>> eqAreEqual = logical(simplify(eq1-eq2) == 0)
eqAreEqual =
logical
1 % True!
>> eqAreEqual = isequal(simplify(eq1), simplify(eq2))
eqAreEqual =
logical
1 % Also true!
答案 1 :(得分：2)
对于符号数学和Matlab R2012a +，一般来说，最好使用isAlways来检查是否存在相等或不等式。对于你的例子，
import os
import os.path
import fnmatch
import logging
import ycm_core
import re
BASE_FLAGS = [
'-Wall',
'-Wextra',
'-Werror',
'-Wno-long-long',
'-Wno-variadic-macros',
'-fexceptions',
'-ferror-limit=10000',
'-DNDEBUG',
'-std=c++1z',
'-xc++',
'-I/usr/lib/',
'-I/usr/include/'
]
SOURCE_EXTENSIONS = [
'.cpp',
'.cxx',
'.cc',
'.c',
'.m',
'.mm'
]
SOURCE_DIRECTORIES = [
'src',
'lib'
]
HEADER_EXTENSIONS = [
'.h',
'.hxx',
'.hpp',
'.hh'
]
HEADER_DIRECTORIES = [
'include'
]
BUILD_DIRECTORY = 'build';
def IsHeaderFile(filename):
extension = os.path.splitext(filename)[1]
return extension in HEADER_EXTENSIONS
def GetCompilationInfoForFile(database, filename):
if IsHeaderFile(filename):
basename = os.path.splitext(filename)[0]
for extension in SOURCE_EXTENSIONS:
# Get info from the source files by replacing the extension.
replacement_file = basename + extension
if os.path.exists(replacement_file):
compilation_info = database.GetCompilationInfoForFile(replacement_file)
if compilation_info.compiler_flags_:
return compilation_info
# If that wasn't successful, try replacing possible header directory with possible source directories.
for header_dir in HEADER_DIRECTORIES:
for source_dir in SOURCE_DIRECTORIES:
src_file = replacement_file.replace(header_dir, source_dir)
if os.path.exists(src_file):
compilation_info = database.GetCompilationInfoForFile(src_file)
if compilation_info.compiler_flags_:
return compilation_info
return None
return database.GetCompilationInfoForFile(filename)
def FindNearest(path, target, build_folder=None):
candidate = os.path.join(path, target)
if(os.path.isfile(candidate) or os.path.isdir(candidate)):
logging.info("Found nearest " + target + " at " + candidate)
return candidate;
parent = os.path.dirname(os.path.abspath(path));
if(parent == path):
raise RuntimeError("Could not find " + target);
if(build_folder):
candidate = os.path.join(parent, build_folder, target)
if(os.path.isfile(candidate) or os.path.isdir(candidate)):
logging.info("Found nearest " + target + " in build folder at " + candidate)
return candidate;
return FindNearest(parent, target, build_folder)
def MakeRelativePathsInFlagsAbsolute(flags, working_directory):
if not working_directory:
return list(flags)
new_flags = []
make_next_absolute = False
path_flags = [ '-isystem', '-I', '-iquote', '--sysroot=' ]
for flag in flags:
new_flag = flag
if make_next_absolute:
make_next_absolute = False
if not flag.startswith('/'):
new_flag = os.path.join(working_directory, flag)
for path_flag in path_flags:
if flag == path_flag:
make_next_absolute = True
break
if flag.startswith(path_flag):
path = flag[ len(path_flag): ]
new_flag = path_flag + os.path.join(working_directory, path)
break
if new_flag:
new_flags.append(new_flag)
return new_flags
def FlagsForClangComplete(root):
try:
clang_complete_path = FindNearest(root, '.clang_complete')
clang_complete_flags = open(clang_complete_path, 'r').read().splitlines()
return clang_complete_flags
except:
return None
def FlagsForInclude(root):
try:
include_path = FindNearest(root, 'include')
flags = []
for dirroot, dirnames, filenames in os.walk(include_path):
flags = flags + ["-I" + dirroot]
for dir_path in dirnames:
real_path = os.path.join(dirroot, dir_path)
flags = flags + ["-I" + real_path]
return flags
except:
return None
def FlagsForCompilationDatabase(root, filename):
try:
# Last argument of next function is the name of the build folder for
# out of source projects
compilation_db_path = FindNearest(root, 'compile_commands.json', BUILD_DIRECTORY)
compilation_db_dir = os.path.dirname(compilation_db_path)
logging.info("Set compilation database directory to " + compilation_db_dir)
compilation_db = ycm_core.CompilationDatabase(compilation_db_dir)
if not compilation_db:
logging.info("Compilation database file found but unable to load")
return None
compilation_info = GetCompilationInfoForFile(compilation_db, filename)
if not compilation_info:
logging.info("No compilation info for " + filename + " in compilation database")
return None
return MakeRelativePathsInFlagsAbsolute(
compilation_info.compiler_flags_,
compilation_info.compiler_working_dir_)
except:
return None
def FlagsForFile(filename):
root = os.path.realpath(filename);
compilation_db_flags = FlagsForCompilationDatabase(root, filename)
if compilation_db_flags:
final_flags = compilation_db_flags
else:
final_flags = BASE_FLAGS
clang_flags = FlagsForClangComplete(root)
if clang_flags:
final_flags = final_flags + clang_flags
include_flags = FlagsForInclude(root)
if include_flags:
final_flags = final_flags + include_flags
return {
'flags': final_flags,
'do_cache': True
}
返回逻辑isAlways(eq1==eq2)
（true）。 1函数考虑假设并且可以优雅地处理不可判定的条件。来自@gnovice的解决方案可以在较旧版本的Matlab中使用，但在表达式无法证明时会抛出错误，例如isAlways。