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When a string of mixed alphabets and numerals is presented for human interpretation, ambiguities arise. The most obvious is the similarity of the letters I, O and Q to the numbers 1 and 0. [3] Therefore, depending on the application, various subsets of the alphanumeric were adopted to avoid misinterpretation by humans.
checks whether the operand is alphanumeric isalpha: iswalpha: checks whether the operand is alphabetic islower: iswlower: checks whether the operand is lowercase isupper: iswupper: checks whether the operand is an uppercase isdigit: iswdigit: checks whether the operand is a digit isxdigit: iswxdigit: checks whether the operand is hexadecimal ...
rfind(string,substring) returns integer Description Returns the position of the start of the last occurrence of substring in string. If the substring is not found most of these routines return an invalid index value – -1 where indexes are 0-based, 0 where they are 1-based – or some value to be interpreted as Boolean FALSE. Related instr
For instance, the lexical grammar for many programming languages specifies that a string literal starts with a " character and continues until a matching " is found (escaping makes this more complicated), that an identifier is an alphanumeric sequence (letters and digits, usually also allowing underscores, and disallowing initial digits), and ...
In SGML, HTML and XML documents, the logical constructs known as character data and attribute values consist of sequences of characters, in which each character can manifest directly (representing itself), or can be represented by a series of characters called a character reference, of which there are two types: a numeric character reference and a character entity reference.
Character entity references can also have the format &name; where name is a case-sensitive alphanumeric string. For example, "λ" can also be encoded as λ in an HTML document. The character entity references < , > , " and & are predefined in HTML and SGML, because < , > , " and & are already used to delimit markup.
The Luhn mod N algorithm generates a check digit (more precisely, a check character) within the same range of valid characters as the input string. For example, if the algorithm is applied to a string of lower-case letters (a to z), the check character will also be a lower-case letter. Apart from this distinction, it resembles very closely the ...
A string literal or anonymous string is a literal for a string value in the source code of a computer program. Modern programming languages commonly use a quoted sequence of characters, formally "bracketed delimiters", as in x = "foo", where , "foo" is a string literal with value foo. Methods such as escape sequences can be used to avoid the ...