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A string is a prefix [1] of a string if there exists a string such that =. A proper prefix of a string is not equal to the string itself; [2] some sources [3] in addition restrict a proper prefix to be non-empty. A prefix can be seen as a special case of a substring.
For example, in C#, the "@" prefix can be used either for stropping (to allow reserved words to be used as identifiers), or as a prefix to a literal (to indicate a raw string); in this case neither use is a sigil, as it affects the syntax of identifiers or the semantics of literals, not the semantics of identifiers.
In Python, if a name is intended to be "private", it is prefixed by one or two underscores. Private variables are enforced in Python only by convention. Names can also be suffixed with an underscore to prevent conflict with Python keywords. Prefixing with double underscores changes behaviour in classes with regard to name mangling.
The following example represents an n-to-1 relationship between movies and their directors. It is shown how user-defined Python classes create corresponding database tables, how instances with relationships are created from either side of the relationship, and finally how the data can be queried — illustrating automatically generated SQL ...
For example, in some forms of BASIC, name$ names a string and count% names an integer. The major difference between Hungarian notation and sigils is that sigils declare the type of the variable in the language, whereas Hungarian notation is purely a naming scheme with no effect on the machine interpretation of the program text.
If n is greater than the length of the string then most implementations return the whole string (exceptions exist – see code examples). Note that for variable-length encodings such as UTF-8, UTF-16 or Shift-JIS, it can be necessary to remove string positions at the end, in order to avoid invalid strings.
For example, in Python, raw strings are preceded by an r or R – compare 'C:\\Windows' with r'C:\Windows' (though, a Python raw string cannot end in an odd number of backslashes). Python 2 also distinguishes two types of strings: 8-bit ASCII ("bytes") strings (the default), explicitly indicated with a b or B prefix, and Unicode strings ...
As another example, in Pascal, div and mod are reserved words used as operators (integer division and remainder). There may also be reserved words which have no defined meaning. For example, in Java, goto and const are listed as reserved words, but are not otherwise mentioned in the Java syntax rules.