(1800.1899) = 1844 is false, since the types are different (Range vs. For example, a value of type Range is a range of integers, such as 1800.1899. The = operator is flexible and may be defined arbitrarily for any given type. In Ruby, equality under = requires both operands to be of identical type, e.g. For this reason it is recommended to avoid the = operator in JavaScript in favor of =. The expression 0 = false is true, but 0 = undefined is false, even though both sides of the = act the same in Boolean context. However, in JavaScript the behavior of = cannot be described by any simple consistent rules. JavaScript has the same semantics for =, referred to as "equality without type coercion". For instance, the expression 0 = false is true, but 0 = false is not, because the number 0 is an integer value whereas false is a Boolean value. In PHP, the triple equals sign ( =) denotes identity, meaning that not only do the two expressions evaluate to equal values, they are also of the same data type. 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. Following ALGOL, most languages that use "=" for equality use ":=" for assignment, although APL, with its special character set, uses a left-pointing arrow.įortran 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." to test for equality. However, in most languages where "=" has one of these meanings, a different character or, more often, a sequence of characters is used for the other meaning.
But "=" is used for equality and not assignment in the Pascal family, Ada, Eiffel, APL, and other languages.Ī few languages, such as BASIC and PL/I, have used the equals sign to mean both assignment and equality, distinguished by context. As well as Fortran, "=" is used for assignment in such languages as C, Perl, Python, awk, and their descendants. The equals sign was reserved for this usage.īoth usages have remained common in different programming languages into the early 21st century. ALGOL included a relational operator that tested for equality, allowing constructions like if x = 2 with essentially the same meaning of "=" as the conditional usage in mathematics. For example, the assignment X = X + 2 increases the value of X by 2.Ī rival programming-language usage was pioneered by the original version of ALGOL, which was designed in 1958 and implemented in 1960. This somewhat resembles the use of "=" in a mathematical definition, but with different semantics: the expression following "=" is evaluated first and may refer to a previous value of X. In Fortran, "=" serves as an assignment operator: X = 2 sets the value of X to 2. The first important computer programming language to use the equals sign was the original version of Fortran, FORTRAN I, designed in 1954 and implemented in 1957. In mathematics, the equals sign can be used as a simple statement of fact in a specific case (x = 2), or to create definitions (let x = 2), conditional statements (if x = 2, then …), or to express a universal equivalence (x + 1) 2 = x 2 + 2x + 1. Usage in mathematics and computer programming The symbol || was used by some and æ (or œ), from the Latin word aequalis meaning equal, was widely used into the 1700s. … to avoid the tedious repetition of these words: "is equal to", I will set (as I do often in work use) a pair of parallels, or Gemowe lines, of one length (thus =), because no two things can be more equal.Īccording to Scotland's University of St Andrews History of Mathematics website: The symbol '=' was not immediately popular. … to auoide the tediouſe repetition of theſe woordes : is equalle to : I will ſette as I doe often in woorke vſe, a paire of paralleles, or Gemowe lines of one lengthe, thus: =, bicauſe noe. In his book Recorde explains his design of the "Gemowe lines" (meaning twin lines, from the Latin gemellus ): The original form of the symbol was much wider than the present form. The "=" symbol that is now universally accepted in mathematics for equality was first recorded by Welsh mathematician Robert Recorde in The Whetstone of Witte (1557).
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