Sigil (computer programming)

In computer programming, a sigil (ˈsɪdʒəl) is a symbol affixed to a variable name, showing the variable's datatype or scope, usually a prefix, as in $foo, where$ is the sigil. Sigil, from the Latin sigillum, meaning a "little sign", means a sign or image supposedly having magical power. Sigils can be used to separate and demarcate namespaces that possess different properties or behaviors. The use of sigils was popularized by the BASIC programming language. The best known example of a sigil in BASIC is the dollar sign ("$") appended to the names of all strings. Consequently, programmers outside America tend to pronounce$ as "string" instead of "dollar". Many BASIC dialects use other sigils (like "%") to denote integers and floating-point numbers and their precision, and sometimes other types as well. Larry Wall adopted shell scripting's use of sigils for his Perl programming language. In Perl, the sigils do not specify fine-grained data types like strings and integers, but the more general categories of scalars (using a prefixed "$"), arrays (using "@"), hashes (using "In CLIPS, scalar variables are prefixed with a "?" sigil, while multifield (e.g., a 1-level list) variables are prefixed with "$?". In Common Lisp, special variables (with dynamic scope) are typically surrounded with * in what is called the "earmuff convention". While this is only convention, and not enforced, the language itself adopts the practice (e.g., standard-output). Similarly, some programmers surround constants with +. In CycL, variables are prefixed with a "?" sigil. Similarly, constant names are prefixed with "#$" (pronounced "hash-dollar"). In Elixir, sigils are provided via the "~" symbol, followed by a letter to denote the type of sigil, and then delimiters.