The %strlen macro is like %assign macro in that it creates (or redefines) a numeric value to a macro. The difference is that with %strlen, the numeric value is the length of a string. An example of the use of this would be:

%strlen charcnt 'my string'

In this example, charcnt would receive the value 8, just as if an %assign had been used. In this example, 'my string' was a literal string but it could also have been a single-line macro that expands to a string, as in the following example:

%define sometext 'my string'
%strlen charcnt sometext

As in the first case, this would result in charcnt being assigned the value of 8.

Individual letters in strings can be extracted using %substr. An example of its use is probably more useful than the description:

%substr mychar  'xyz' 1         ; equivalent to %define mychar 'x'
%substr mychar  'xyz' 2         ; equivalent to %define mychar 'y'
%substr mychar  'xyz' 3         ; equivalent to %define mychar 'z'

In this example, mychar gets the value of 'y'. As with %strlen (see Раздел 3.2.1), the first parameter is the single-line macro to be created and the second is the string. The third parameter specifies which character is to be selected. Note that the first index is 1, not 0 and the last index is equal to the value that %strlen would assign given the same string. Index values out of range result in an empty string.