How To Detect Special Characters

How could I find out if there are any special characters in my string? Suppose I have the string '1asdf?', how could I detect if there is a special character in there?

[Cedric]

What is the purpose? Do you need a true/false type of answer, the position of special characters, to eliminate them, ..? How to you define "special"?

[William Nelson]

I need a true and false answer and a special character is anything that is not abc or 123. ?"{} would all be special characters.

Answer 1

[Steven Lord]

Use isstrprop with category 'alphanum' to identify letters and digits.

Answer 2

[per isakson]

>> str = regexp( '1asdf?', '[^\w]', 'match' )
str = 
    '?'

where I defined not being special as "Any alphabetic, numeric, or underscore character. For English character sets, \w is equivalent to [a-zA-Z_0-9]"

In response to comment

"I need a true and false answer and a special character is anything that is not abc or 123. ?"{} would all be special characters."

>> str = '1a$s#df?';
>> is_special = false( size( str ) );
>> is_special( regexp( str, '[^a-zA-Z0-9.?"{}]' ) ) = true
is_special =
     0     0     1     0     1     0     0     0
>>

I assumed that "123" is short for "0123456789". However, after a second reading

is_special( regexp( str, '[^123abc]' ) ) = true
is_special =
   0     0     1     1     1     1     1     1
>>

[Cedric]

 '[^\w]' = '\W'

[per isakson]

Good point!

[Cedric]

Given your comment after Per answered, William, which seems to indicate that the underscore '_' is a special character, I think that you want a variant of Per's solution:

 >> specials = regexp( '1as_df?980{}', '[^A-Za-z0-9]', 'match' )
 specials =
  1×4 cell array
    '_'    '?'    '{'    '}'

or

 >> specialsPos = regexp( '1as_df?980{}', '[^A-Za-z0-9]', 'start' )
 specialsPos =
     4     7    11    12

or

 >> isOk = isempty( regexp( '1as_df?980{}', '[^A-Za-z0-9]', 'start' ))
 isOk =
  logical
   0

where the pattern fully defines characters that are not special, and eliminate the underscore which is not matched by \W.

[per isakson]

A typesetter shall follow the manuscript even if it blows out of the window. Does that make sense in English?

One more answer

>> isvarname('1a$s#df?')
ans =
     0