How to select a specific .m function when two exist?

Question

First, here the way i\'m calling the function :

eval([functionName \'(\'\'stringArg\'\')\']); % functionName = \'someStringForTheFunctionName\'

Answer 1

Function names must be unique in MATLAB. If they are not, so there are duplicate names, then MATLAB uses the first one it finds on your search path.

Having said that, there are a few options open to you.

Option 1. Use @ directories, putting each version in a separate directory. Essentially you are using the ability of MATLAB to apply a function to specific classes. So, you might set up a pair of directories:

@char
@double

Put your copies of myfun.m in the respective directories. Now when MATLAB sees a double input to myfun, it will direct the call to the double version. When MATLAB gets char input, it goes to the char version.

BE CAREFUL. Do not put these @ directories explicitly on your search path. DO put them INSIDE a directory that is on your search path.

A problem with this scheme is if you call the function with a SINGLE precision input, MATLAB will probably have a fit, so you would need separate versions for single, uint8, int8, int32, etc. You cannot just have one version for all numeric types.

Option 2. Have only one version of the function, that tests the first argument to see if it is numeric or char, then branches to perform either task as appropriate. Both pieces of code will most simply be in one file then. The simple scheme will have subfunctions or nested functions to do the work.

Option 3. Name the functions differently. Hey, its not the end of the world.

Option 4: As Shaun points out, one can simply change the current directory. MATLAB always looks first in your current directory, so it will find the function in that directory as needed. One problem is this is time consuming. Any time you touch a directory, things slow down, because there is now disk input needed.

The worst part of changing directories is in how you use MATLAB. It is (IMHO) a poor programming style to force the user to always be in a specific directory based on what code inputs they wish to run. Better is a data driven scheme. If you will be reading in or writing out data, then be in THAT directory. Use the MATLAB search path to categorize all of your functions, as functions tend not to change much. This is a far cleaner way to work than requiring the user to migrate to specific directories based on how they will be calling a given function.

Personally, I'd tend to suggest option 2 as the best. It is clean. It has only ONE main function that you need to work with. If you want to keep the functions district, put them as separate nested or sub functions inside the main function body. Inside of course, they will have distinct names, based on how they are driven.