In software, a wildcard character is a kind of placeholder represented by a single character, such as an asterisk (*), which can be interpreted as a number of literal characters or an empty string. It is often used in file searches so the full name need not be typed.
⭐ Core Definition: Wildcard character
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👉 Wildcard character in the context of Free variables and bound variables
In mathematics, and in other disciplines involving formal languages, including mathematical logic and computer science, a variable may be said to be either free or bound. Some older books use the terms real variable and apparent variable for free variable and bound variable, respectively. A free variable is a notation (symbol) that specifies places in an expression where substitution may take place and is not a parameter of this or any container expression. The idea is related to a placeholder (a symbol that will later be replaced by some value), or a wildcard character that stands for an unspecified symbol.
In computer programming, the term free variable refers to variables used in a function that are neither local variables nor parameters of that function. The term non-local variable is often a synonym in this context.
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Wildcard character in the context of Google Ngrams
The Google Books Ngram Viewer is an online search engine that charts the frequencies of any set of search strings using a yearly count of n-grams found in printed sources published between 1500 and 2022 in Google's text corpora in English, Chinese (simplified), French, German, Hebrew, Italian, Russian, or Spanish.There are also some specialized English corpora, such as American English, British English, and English Fiction.
The program can search for a word or a phrase, including misspellings or gibberish. The n-grams are matched with the text within the selected corpus, and if found in 40 or more books, are then displayed as a graph. The Google Books Ngram Viewer supports searches for parts of speech and wildcards. It is routinely used in research.