Programming Upgrade Issues :: (MATLAB Release Notes)

MATLAB Release Notes

Programming Upgrade Issues

The issues involved in upgrading from MATLAB 7.0 to MATLAB 7.0.1, in terms of programming features, are

ftell Returning Invalid Position in Rare Cases

The ftell function is likely to return an invalid position when all of the following are true. This is due to the way in which the Microsoft Windows C library currently handles its ftell and fgetpos commands:

The file you are currently operating on is an ASCII text file.
The file was written on a UNIX-based system, or uses the UNIX-style line terminator: a line feed (with no carriage return) at the end of each line of text. (This is the default output format for MATLAB functions dlmwrite and csvwrite.)
You are reading the file on a Windows system.
You opened the file with the fopen function with mode set to 'rt'.
The ftell command is directly preceded by an fgets command.

Note that this does not affect the ability to accurately read from and write to this type of file from MATLAB.

Using the | Operator in regexp Expressions

Be careful about using the logical OR (|) operator within square brackets (e.g., [A|B]) in regular expressions in MATLAB. The recommended way to match "the letter A or the letter B" in a MATLAB regexp expression is to use '[AB]'. If you have used '[A|B]' for this purpose in earlier versions of MATLAB, you may get unexpected results when you run your code in version 7.0.

MATLAB versions 6.0 and 6.5 treat | as an ordinary character when it is used between square brackets. For example, these versions interpret the expression '[A|B]' as "match 'A', or match '|', or match 'B'." MATLAB 7.0 correctly gives precedence to the logical OR functionality of the | operator. Because of this change, MATLAB now interprets '[A|B]' as "match '[A', or match 'B]'."

You can avoid the effects of this bug fix altogether by using the recommended syntax '[AB]' for this type of operation. This syntax returns the correct results in all MATLAB versions.

The following example attempts to find the word Jill or Bill in the string 'My name is Bill'. The syntax used in the expression is incorrect, but regexp in MATLAB 6.5 finds a match anyway because of the software bug. This syntax does not work in version 7.0 or 7.0.1 because MATLAB now interprets the expression as the logical OR of the two statements, '[J' and 'B]ill':

    - MATLAB 6.5 -                    - MATLAB 7.0.1 -
str = 'My name is Bill';          str = 'My name is Bill';
expr = '[J|B]ill';                expr = '[J|B]ill';
[s e] = regexp(str, expr);        [s e] = regexp(str, expr);
str(s:e)                          str(s:e)
ans =                             ans =
   Bill                              Empty string: 1-by-0

Using the recommended syntax returns the correct results in all MATLAB versions:

str = 'My name is Bill';
expr = '[JB]ill';
[s e] = regexp(str, expr);
str(s:e)
ans =
   Bill

If you want to use | in an expression as an ordinary character, precede it with a backslash:

str = 'The | operator performs a logical OR';
expr = 'The [\$ \| \#] operator';
[s e] = regexp(str, expr);
str(s:e)
ans =
   The | operator

Multiple Declarations of Persistent Variables

You can no longer declare a variable as persistent more than once within a function.

Passing Empty Date Strings to datevec

For the purpose of backwards compatibility, invoking the command datevec('') now returns an empty vector. This behavior was not intentional in previous versions of MATLAB, and it is subject to change in future releases.

Mathematics Upgrade Issues External Interface/API Upgrade Issues