How do I avoid "ArithmeticException integer overflow" in Clojure?

Question

It seems to happen all the time. For example:

(apply * (range 1 101))

gives me the error

ArithmeticException integer overflow  clojure.lang.Numbers.throwIntOverflow (Numbers.java:1374)

While in Ruby 1.9.2 the (conceptually) equivalent code,

(1..100).reduce(:*)

produces the desired result of

93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000

Obviously the two languages are quite different under the hood but it seems like they should both be able to handle this calculation without issue. Am I doing something wrong here? Or do I have an incorrect understanding?

Which Clojure version you are using..? Wich Clojure 1.2.0, I got, 93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000 — Abimaran Kugathasan
– Abimaran Kugathasan, Commented Jan 7, 2012 at 5:31

Steve Wang · Accepted Answer · 2012-01-07 05:33:26Z

43

You need to use some form of BigInteger.

Try (apply *' (range 1 101)).

(see http://dev.clojure.org/display/doc/Documentation+for+1.3+Numerics -- evidently this auto-promotes upon overflow?)

answered Jan 7, 2012 at 5:33

Steve Wang

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1 Comment

bitops Over a year ago

I accepted your answer but it seems like it didn't take. Let me know if it doesn't go through. Want to give credit where it's due!

dongpf · Accepted Answer · 2014-10-04 15:20:58Z

8

From Clojure 1.3, you should cast Integer(or Long) to BigInt explicitly, otherwise there will be "ArithmeticException integer overflow" error when the number is too large.

There are three solutions, please pick the one you favor:

use one of the auto-promoting math functions:+', -', *', /', inc', dec'

example: (apply *' (range 1 101))
use the BigInt type cast function

example: (apply * (range (bigint 1) 101))
change to BigInt numeric literal

example: (apply * (range 1N 101))

Reference: Documentation for Clojure 1.3 Numerics

edited Oct 4, 2014 at 15:20

answered Oct 4, 2014 at 15:10

dongpf

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Kenny Evitt · Accepted Answer · 2015-10-13 13:22:27Z

6

Ruby has auto-promoting calculations, changing to a bigger bittype number when the result overflows its type. Because of performance considerations, calculations from Clojure 1.3 up will not be auto-promoting, and you need to take into account if a calculation can overflow, or use one of the auto-promoting math functions (+', -', *', /') if performance wouldn't be an issue.

edited Oct 13, 2015 at 13:22

Kenny Evitt

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answered Jan 7, 2012 at 13:44

NielsK

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BLUEPIXY · Accepted Answer · 2012-01-07 12:51:49Z

1

in 1.3.0

(apply * (range 1N 101N));clojure.lang.BigInt

(apply * (range 1M 101M));java.math.BigDecimal

edited Jan 7, 2012 at 12:51

answered Jan 7, 2012 at 9:13

BLUEPIXY

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cskksc · Accepted Answer · 2014-06-11 06:43:11Z

1

Stumbled onto the same situation. For me using "1.0" instead of "1" did the trick.

(apply * (range 1.0 1000))

As documented, there is a difference between floats and decimals.

answered Jun 11, 2014 at 6:43

cskksc

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Andrew Cooper · Accepted Answer · 2012-01-07 05:33:28Z

0

I don't know Clojure, but it looks like it's using 32-bit or 64-bit integers to do the calculation. 32-bit signed integers have a maximum value of 2^31 - 1 (a bit over 2*10^9). 64-bit integers have a max value of 2^64 - 1 (a bit over 4*10^18). The value you got from Ruby is much higher than that.

Obviously Ruby is using some other number representation under the hood.

answered Jan 7, 2012 at 5:33

Andrew Cooper

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