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You're viewing version 1.2.0 of cond. The latest stable version of Clojure Core is 1.3.0.

1.2.0

1.2.0
1.3.0

cond

Takes a set of test/expr pairs. It evaluates each test one at a
time. If a test returns logical true, cond evaluates and returns
the value of the corresponding expr and doesn't evaluate any of the
other tests or exprs. (cond) returns nil.

4 Examples top

link | changes
```
(defn pos-neg-or-zero
  "Determines whether or not n is positive, negative, or zero"
  [n]
  (cond
    (< n 0) "negative"
    (> n 0) "positive"
    :else "zero"))

user=> (pos-neg-or-zero 5)
"positive"
user=> (pos-neg-or-zero -1)
"negative"
user=> (pos-neg-or-zero 0)
"zero"
```
(defn pos-neg-or-zero "Determines whether or not n is positive, negative, or zero" [n] (cond (< n 0) "negative" (> n 0) "positive" :else "zero")) user=> (pos-neg-or-zero 5) "positive" user=> (pos-neg-or-zero -1) "negative" user=> (pos-neg-or-zero 0) "zero"
link | changes
```
user=> (let [grade 85]
         (cond
           (>= grade 90) "A"
           (>= grade 80) "B"
           (>= grade 70) "C"
           (>= grade 60) "D"
           :else "F"))
"B"
```
user=> (let [grade 85] (cond (>= grade 90) "A" (>= grade 80) "B" (>= grade 70) "C" (>= grade 60) "D" :else "F")) "B"
link | changes
```
;; See examples for "if" explaining Clojure's idea of logical true
;; and logical false.
```
;; See examples for "if" explaining Clojure's idea of logical true ;; and logical false.
link | changes
```
;; Generates a random number compares it to user input
(let [rnd (rand-int 10)
      guess (Integer/parseInt (read-line))]
  (cond
    (= rnd guess) (println "You got my guess right!")
    :else (println "Sorry... guess again!")))
```
;; Generates a random number compares it to user input (let [rnd (rand-int 10) guess (Integer/parseInt (read-line))] (cond (= rnd guess) (println "You got my guess right!") :else (println "Sorry... guess again!")))

Source clojure/core.clj:491 top

(defmacro cond
  "Takes a set of test/expr pairs. It evaluates each test one at a
  time.  If a test returns logical true, cond evaluates and returns
  the value of the corresponding expr and doesn't evaluate any of the
  other tests or exprs. (cond) returns nil."
  {:added "1.0"}
  [& clauses]
    (when clauses
      (list 'if (first clauses)
            (if (next clauses)
                (second clauses)
                (throw (IllegalArgumentException.
                         "cond requires an even number of forms")))
            (cons 'clojure.core/cond (next (next clauses))))))

Vars in clojure.core/cond: cons defmacro first list next second when

Used in 91 other vars (expand)

with-open comparator keyword bigdec bigint every? doc collection-tag list-model skip-whitespace skip-if-eol replace replace-first assert-expr walk encode make-map handler-case get-cell cell read-ns-decl jmx->clj abs lcm monad-transformer ancestor? pprint-defn rtrim pprint-simple-default compile-format normalize-cond get-connection do-swing* assert-expr match xml-> nrow trans ncol truncated-variance area-chart* stacked-area-chart* $ view add-pointer add-categories* stacked-bar-chart* group-on bar-chart* line-chart* to-vect query-to-pred combine-with length infix-to-prefix diag make-matrix bind-rows transform-with write-cell background tint fill stroke deriv* eval-in-project result-color dot result-string run-test exit-code should-body annotate text transform operator-arglist maybe-ns eval-for-emacs thread-for-evaluation dispatch-event path-class-files inspectee-title inspector-pop inspector-next emacs-inspect inspect-in-emacs partial-namespace-matcher namespace-matcher tree-map group-container-args combinations

Comments top

1 comment(s) for cond.

blais

link

We should add a comment in the docstring for the final usage of :else.

ClojureDocs(beta)