file string-expression (is | isnt) readable

This operator returns true if the file named by the string expression is readable by the OmniMark program. This can be done before executing an action that requires a readable file. If the file does not exist, it is (obviously) not readable.

If the file does not exist or is not readable, the programmer can choose an alternative path.

For example, the following code tests whether or not a file exists or is readable and, if not, it notes the error:

  find "\input{" [any except "}"]+ => filename "}"
    do when file filename is readable
      submit file filename
    else
      put #error "File %x(filename) doesn't exist.%n"
      put #error "Processing continues... %n"
    done