clojure.core/==

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Type: function Added: Clojure 1.0 Examples: 6 Runnable: 5

([x] [x y] [x y & more])

Returns non-nil if nums all have the equivalent value (type-independent), otherwise false

Examples

by james on 2010-09-02 . May have evaluation errors. ▶

;; true: (== 1) (== 1 1) (== 1/1, 2/2, 3/3, 4/4) (== 1, 1.0, 1/1) (== :foo) ;; false: (== 1 2) ;; ClassCastException (== 1 \1) (== 1 "1")

by h3x3d on 2014-11-06 ▶

(= 0.0 0) false (== 0.0 0) true

by phreed on 2014-11-10 ▶

;; Just what you would expect (== 2.0 1.9999999) ;;=> false ;; a suprising result (== 2.0 2 6/3 1.9999999999999999) ;;=> true ??!? ;; Yes, there is some rounding off going on. ;; if you take off just one of the repeating 9 (on my machine) these compare.

by wontheone1 on 2017-09-08 ▶

;; When floating point numbers are far enough from each other (== 2.0 1.9999999) ;;=> false (- 100.0 100.00000000000001) ;13(Thirteen) 0s after floating point in the last number ;;=> -1.4210854715202004E-14 ;; When two floating point numbers are too close some basic algebraic properties don't strictly hold. (== 2.0 1.9999999999999999) ;;=> true (* 100 (- 1.0 1.0000000000000001)) ;15(fifteen) 0s after floating point in the last number ;;=> 0.0 ;; They are still different types (= 2 1.9999999999999999) ;;=> false ;; see more from https://en.wikibooks.org/wiki/Floating_Point/Epsilon ;; I found above example was distracting by putting 6/3 and 2 in the equality check that is why I decided to write up a similar but new example.

by jafingerhut on 2019-01-29 ▶

;; See the Clojure Equality guide for more details: ;; https://clojure.org/guides/equality ;; == returns false whenever comparing the special "not a number" value to any ;; number, including itself. (== 1 ##NaN) false ;; this result you probably expect (== ##NaN ##NaN) false ;; this one may surprise you

by berczeck on 2020-08-23 ▶

(= 1/2 0.5) ;; => false (== 1/2 0.5) ;; => true

Note by gstamp

There is a difference between "=" and "". For primitives you definitely want to use "" as "=" will result in a cast to the wrapped types for it's arguments.

This may not be the case come Clojure 1.3 (see [1])

[1] http://github.com/clojure/clojure/commit/df8c65a286e90e93972bb69392bc106128427dde

Note by popopome

So what is difference with =?

Note by mattharden

'== is defined only for numbers, where '= is general equality. The example showing (== :foo) as true is a bit misleading because (== :foo :foo) produces an exception. Unary == always returns true as an optimization.

See also

• clojure.core/= (4)
• clojure.core/identical? (3)
• clojure.core/compare (3)

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