range function wrong in 1.7.0-beta?

Mathias De Wachter

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Apr 18, 2015, 3:32:40 PM4/18/15

to clo...@googlegroups.com

Hi,

this looks like quite a serious bug to me (at least it messed up my project):

First taking the code taken from grimoire:

clojurechess.position> (defn range

"Returns a lazy seq of nums from start (inclusive) to end

(exclusive), by step, where start defaults to 0, step to 1, and end to

infinity. When step is equal to 0, returns an infinite sequence of

start. When start is equal to end, returns empty list."

{:added "1.0"

:static true}

([] (range 0 Double/POSITIVE_INFINITY 1))

([end] (range 0 end 1))

([start end] (range start end 1))

([start end step]

(lazy-seq

(let [b (chunk-buffer 32)

comp (cond (or (zero? step) (= start end)) not=

(pos? step) <

(neg? step) >)]

(loop [i start]

(if (and (< (count b) 32)

(comp i end))

(do

(chunk-append b i)

(recur (+ i step)))

(chunk-cons (chunk b)

(when (comp i end)

(range i end step)))))))))

WARNING: range already refers to: #'clojure.core/range in namespace: clojurechess.position, being replaced by: #'clojurechess.position/range

#'clojurechess.position/range

clojurechess.position> (range 0 11 2)

(0 2 4 6 8 10)

which is what I'd expect and relied on.

Now, looking at the new code:

clojurechess.position> (clojure.repl/source clojure.core/range)

(defn range

"Returns a lazy seq of nums from start (inclusive) to end

(exclusive), by step, where start defaults to 0, step to 1, and end to

infinity. When step is equal to 0, returns an infinite sequence of

start. When start is equal to end, returns empty list."

{:added "1.0"

:static true}

([]

(iterate inc' 0))

([end]

(if (instance? Long end)

(clojure.lang.LongRange/create end)

(clojure.lang.Range/create end)))

([start end]

(if (and (instance? Long start) (instance? Long end))

(clojure.lang.LongRange/create start end)

(clojure.lang.Range/create start end)))

([start end step]

(if (and (instance? Long start) (instance? Long end) (instance? Long step))

(clojure.lang.LongRange/create start end step)

(clojure.lang.Range/create start end step))))

nil

clojurechess.position> (clojure.lang.Range/create 0 11 2)

(0 2 4 6 8 10)

clojurechess.position> (clojure.lang.LongRange/create 0 11 2)

(0 2 4 6 8)

clojurechess.position> (clojure.core/range 0 11 2)

(0 2 4 6 8)

So the culprit is clojure.lang.LongRange/create.

Nelson Morris

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Apr 18, 2015, 5:00:28 PM4/18/15

to Clojure

I was trying to write a test.check property for this, and it seems to have a found a different bug around `count` and `range`.

```

*clojure-version*

;;=> {:major 1, :minor 7, :incremental 0, :qualifier "beta1"}

(require '[clojure.test.check :as tc])

(require '[clojure.test.check.generators :as gen])

(require '[clojure.test.check.properties :as prop])

(def range-count-is-ceil-of-space-divided-by-step

(prop/for-all [start gen/int

end gen/int

step (gen/such-that #(> % 0)

gen/nat)]

(= (count (range start end step))

(long (Math/ceil (double (/ (max 0 (- end start)) step)))))))

(tc/quick-check 100 range-count-is-ceil-of-space-divided-by-step)

;;=> {:result false, :seed 1429389499284, :failing-size 5, :num-tests 6, :fail [-2 -1 3], :shrunk {:total-nodes-visited 9, :depth 3, :result false, :smallest [-1 0 2]}}

(range -1 0 2)

;;=> (-1)

(count (range -1 0 2))

;;=> 0

(tc/quick-check 100 range-count-is-ceil-of-space-divided-by-step)

;;=> {:result false, :seed 1429389621085, :failing-size 4, :num-tests 5, :fail [-3 4 5], :shrunk {:total-nodes-visited 11, :depth 5, :result false, :smallest [0 1 2]}}

(range 0 1 2)

;;=> (0)

(count (range 0 1 2))

;;=> 0

```

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