MATLAB Programming Fundamentals - MathWorks

Alternatives to the eval Function

In this section...

“Why Avoid the eval Function?” on page 2-87

“Variables with Sequential Names” on page 2-87

“Files with Sequential Names” on page 2-88

“Function Names in Variables” on page 2-89

“Field Names in Variables” on page 2-89

“Error Handling” on page 2-90

Why Avoid the eval Function?

Although the eval function is very powerful and flexible, it is not always the best solution

to a programming problem. Code that calls eval is often less efficient and more difficult

to read and debug than code that uses other functions or language constructs. For

example:

• MATLAB compiles code the first time you run it to enhance performance for future
  runs. However, because code in an eval statement can change at run time, it is not
  compiled.


• Code within an eval statement can unexpectedly create or assign to a variable
  already in the current workspace, overwriting existing data.


• Concatenated character vectors within an eval statement are often difficult to read.
  Other language constructs can simplify the syntax in your code.

For many common uses of eval, there are preferred alternate approaches, as shown in

the following examples.

Variables with Sequential Names

A frequent use of the eval function is to create sets of variables such as A1, A2, ..., An,

but this approach does not use the array processing power of MATLAB and is not

recommended. The preferred method is to store related data in a single array. If the data

sets are of different types or sizes, use a structure or cell array.

For example, create a cell array that contains 10 elements, where each element is a

numeric array:

Alternatives to the eval Function