The IsDigit(char) command determines whether char is a decimal digit. A character is a decimal digit if it is one of the following:

If char is a decimal digit, IsDigit returns true. Otherwise, false is returned.

If char is a string that contains more than one character, then all the characters in the string are tested. The command returns true if the condition is true of all characters in the input string. For the empty string, the tested condition is vacuously true.

The StringTools[IsDigit] command is thread-safe as of Maple 15.

For more information on thread safety, see index/threadsafe.