1844 === (1800..1899) is false, since it is interpreted to mean Integer#=== rather than Range#===.[11]. The = symbol, now universally accepted in mathematics for equality, was first recorded by Welsh mathematician Robert Recorde in The Whetstone of Witte (1557). Additional symbols in Unicode related to the equals sign include:[19]. But = is used for equality and not assignment in the Pascal family, Ada, Eiffel, APL, and other languages. [4] Alternatively, in some texts ⇔ is used with this meaning, while ≡ is used for the higher-level metalogical notion of logical equivalence, according to which two formulas are logically equivalent when all models give them the same value. b In Unicode and ASCII, it has the code point 3D. The equals sign was reserved for this usage. However, in JavaScript the behavior of == cannot be described by any simple consistent rules. Equality of truth values (through bi-implication or logical equivalence), may be denoted by various symbols including =, ~, and ⇔. [18] Usage of this symbol dates back to the early computer interfaces developed at Xerox PARC in the 1980s. if N divides a − b. [7][8] Particularly, in geometry, it may be used either to show that two figures are congruent or that they are identical. The language B introduced the use of == with this meaning, which has been copied by its descendant C and most later languages where = means assignment. g {\displaystyle f\equiv g} In recent years, the equals sign has been used to symbolize LGBT rights. a ) The equals sign is sometimes used incorrectly within a mathematical argument to connect math steps in a non-standard way, rather than to show equality (especially by early mathematics students). [19] It is also similar to the icon frequently used to indicate justified text alignment. for two functions f, g if we have In Unicode and ASCII, it has the code point 3D. [13], This symbol is also sometimes used in place of an equal sign for equations that define the symbol on the left-hand side of the equation, to contrast them with equations in which the terms on both sides of the equation were already defined. Both usages have remained common in different programming languages into the early 21st century. b x For example, a value of type Range is a range of integers, such as 1800..1899. Confusion between the two uses of the sign sometimes persists at the university level. [18][better source needed], Symbols used to denote items that are approximately equal include the following:[1][19]. This article is about the symbol. = ( In an equation, the equals sign is placed between two expressions that have the same value, or for which one studies the conditions under which they have the same value. Following ALGOL, most languages that use = for equality use := for assignment, although APL, with its special character set, uses a left-pointing arrow. A few languages, such as BASIC and PL/I, have used the equals sign to mean both assignment and equality, distinguished by context. The symbol || was used by some and æ (or œ), from the Latin word aequalis meaning equal, was widely used into the 1700s" (History of Mathematics, University of St Andrews).[7]. The symbol has been used since 1995 by the Human Rights Campaign, which lobbies for marriage equality, and subsequently by the United Nations Free & Equal, which promotes LGBT rights at the United Nations. Fortran did not have an equality operator (it was only possible to compare an expression to zero, using the arithmetic IF statement) until FORTRAN IV was released in 1962, since when it has used the four characters .EQ. [9], In Ruby, equality under == requires both operands to be of identical type, e.g. In LaTeX, this is done with the "\neq" command. As well as Fortran, = is used for assignment in such languages as C, Perl, Python, awk, and their descendants. d Arrows in Unicode. = For example, HC≡CH is a common shorthand for acetylene[17] (systematic name: ethyne). Most programming languages, limiting themselves to the 7-bit ASCII character set and typeable characters, use ~=, !=, /=, or <> to represent their Boolean inequality operator. for all x. The symbol used to denote inequation (when items are not equal) is a slashed equals sign ≠ (U+2260). 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