In computer programming, the symbol "?" has a special meaning in many programming languages. In C-descended languages, codice_1 is part of the operator, which is used to evaluate simple boolean conditions. In C# 2.0, the codice_1 modifier is used to handle nullable data types and codice_3 is the null coalescing operator. In the POSIX syntax for regular expressions, such as that used in Perl and Python, codice_1 stands for "zero or one instance of the previous subexpression", i.e. an optional element. In certain implementations of the BASIC programming language, the codice_1 character may be used as a shorthand for the "print" function; in others (notably the BBC BASIC family), codice_1 is used to address a single-byte memory location. In OCaml, the question mark precedes the label for an optional parameter. In Scheme, as a convention, symbol names ending in codice_1 are used for predicates, such as codice_8, codice_9, and codice_10. Similarly, in Ruby, method names ending in codice_1 are used for predicates. In Swift, a type followed by codice_1 denotes an option type; codice_1 is also used in "optional chaining", where if an option value is nil, it ignores the following operations. In APL, codice_1 generates random numbers or a random subset of indices. In Rust, a codice_1 suffix on a function or method call indicates error handling. In SPARQL, the question mark is used to introduce variable names, such as codice_16.