Normally having your\u00a0function know about its caller (other than through the arguments we pass onto the stack) is usually a very bad\u00a0idea in program organization, because it introduces unnecessary coupling and hinders visibility.<\/p>\n
Nonetheless, debugger is a built-in\u00a0feature of MATLAB and it provides dbstack() so you have access to your call stack as part of your program. Normally, I couldn’t come up with legitimate uses of it outside debugging.<\/p>\n
One day, I was trying to\u00a0write a wrapper function that does the idiom (mentioned in my earlier blog post<\/a>)<\/p>\n because I want the code to be self-documenting. Let’s call the function mfilepath(). Turns out it’s a difficult problem because mfilename(‘fullpath’) reports the path of the current function executing it. In the case of a wrapper, it’s the path of the wrapper function, not its caller that you are hoping to extract its path from.<\/p>\n In other words, if you write a wrapper function, it’s\u00a0the\u00a0second layer of the stack that you are interested in. So it can be done with dbstack():<\/p>\n Since exception handling is tightly knit into MATLAB (unlike C++, which you pay for the extra overhead), there aren’t much performance penalty to use a try…catch() block than if I checked if ST actually have a second layer (i.e. has a non-base caller). I can confidently do that because\u00a0there is only one way for this ST(2).file access operation to fail:\u00a0mfullpath() is called from the base workspace.<\/p>\n Speaking of catchy titles, I wonder why Loren Shure, a self-proclaimed lover of puns<\/a>\u00a0and the blogger of the Art of MATLAB,<\/a>\u00a0haven’t exploited the built-in functions ‘who’ and ‘whos’ in her April Fools jokes like<\/p>\n Note that these are legitimate MATLAB syntax that won’t throw you an exception. Unless you have ‘your’, ‘daddy’, ‘let’, ‘the’, ‘dogs’, ‘out’ as variable names, the above will\u00a0quietly show nothing. It’d be hilarious if they pass that as an easter egg in the official MATLAB. They already have ‘why’,<\/p>\n <\/p>\n <\/p>\n <\/p>\nfileparts( mfilename('fullpath') );<\/pre>\nfunction p = mfullpath()\r\n ST = dbstack('completenames');\r\n try\r\n p = ST(2).file;\r\n catch\r\n p = '';\r\n end<\/pre>\nwhos your daddy\r\nwho let the dogs out\r\n<\/pre>\n
why not\r\n\r\nError using rng (line 125)\r\nFirst input must be a nonnegative integer seed less than 2^32, 'shuffle', 'default', or generator settings captured previously using S = RNG.\r\n\r\nError in why (line 10)\r\n dflt = rng(n,'v5uniform');<\/pre>\n