Product over a range

Question

Your task is simple: given two integers \$a\$ and \$b\$, output \$\Pi[a,b]\$; that is, the product of the range between \$a\$ and \$b\$. You may take \$a\$ and \$b\$ in any reasonable format, whether that be arguments to a function, a list input, STDIN, et cetera. You may output in any reasonable format, such as a return value (for functions) or STDOUT. \$a\$ will always be less than \$b\$.

Note that the end may be exclusive or inclusive of \$b\$. I'm not picky. ^_^

Test cases

[a,b) => result
[2,5) => 24
[5,10) => 15120
[-4,3) => 0
[0,3) => 0
[-4,0) => 24

[a,b] => result
[2,5] => 120
[5,10] => 151200
[-4,3] => 0
[0,3] => 0
[-4,-1] => 24

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This is a code-golf, so the shortest program in bytes wins.

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Leaderboard

The Stack Snippet at the bottom of this post generates the catalog from the answers a) as a list of shortest solution per language and b) as an overall leaderboard.

To make sure that your answer shows up, please start your answer with a headline, using the following Markdown template:

## Language Name, N bytes

where N is the size of your submission. If you improve your score, you can keep old scores in the headline, by striking them through. For instance:

## Ruby, <s>104</s> <s>101</s> 96 bytes

If there you want to include multiple numbers in your header (e.g. because your score is the sum of two files or you want to list interpreter flag penalties separately), make sure that the actual score is the last number in the header:

## Perl, 43 + 2 (-p flag) = 45 bytes

You can also make the language name a link which will then show up in the snippet:

## [><>](http://esolangs.org/wiki/Fish), 121 bytes

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body{text-align:left!important}#answer-list,#language-list{padding:10px;width:290px;float:left}table thead{font-weight:700}table td{padding:5px}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <link rel="stylesheet" type="text/css" href="//cdn.sstatic.net/codegolf/all.css?v=83c949450c8b"> <div id="answer-list"> <h2>Leaderboard</h2> <table class="answer-list"> <thead> <tr><td></td><td>Author</td><td>Language</td><td>Size</td></tr></thead> <tbody id="answers"> </tbody> </table> </div><div id="language-list"> <h2>Winners by Language</h2> <table class="language-list"> <thead> <tr><td>Language</td><td>User</td><td>Score</td></tr></thead> <tbody id="languages"> </tbody> </table> </div><table style="display: none"> <tbody id="answer-template"> <tr><td>{{PLACE}}</td><td>{{NAME}}</td><td>{{LANGUAGE}}</td><td>{{SIZE}}</td><td><a href="{{LINK}}">Link</a></td></tr></tbody> </table> <table style="display: none"> <tbody id="language-template"> <tr><td>{{LANGUAGE}}</td><td>{{NAME}}</td><td>{{SIZE}}</td><td><a href="{{LINK}}">Link</a></td></tr></tbody> </table>

Answer 1

Jelly, 2 bytes

rP

Takes two numbers as command line arguments. Try it online.

Note that this is inclusive range. For the cost of a byte (3 bytes), we can make this exclusive:

’rP

Try it online. Note that the arguments must be given in the order b a for this version.

Explanation

Inclusive

a rP b
  r   dyadic atom, creates inclusive range between a and b
   P  computes product of the list

Exclusive

b ’rP a
  ’   decrement b (by default, monadic atoms in dyadic chains operate on the left argument)
   r  range
    P product 

Answer 2

ArnoldC, 522 511 bytes

First post on codegolf !

I had fun doing this. Exclusive range.

LISTEN TO ME VERY CAREFULLY f
I NEED YOUR CLOTHES YOUR BOOTS AND YOUR MOTORCYCLE a
I NEED YOUR CLOTHES YOUR BOOTS AND YOUR MOTORCYCLE b
GIVE THESE PEOPLE AIR
HEY CHRISTMAS TREE r
YOU SET US UP 1
HEY CHRISTMAS TREE l
YOU SET US UP 1
STICK AROUND l
GET TO THE CHOPPER r
HERE IS MY INVITATION r
YOU'RE FIRED a
ENOUGH TALK
GET TO THE CHOPPER a
HERE IS MY INVITATION a
GET UP 1
ENOUGH TALK
GET TO THE CHOPPER l
HERE IS MY INVITATION b
LET OFF SOME STEAM BENNET a
ENOUGH TALK
CHILL
I'LL BE BACK r
HASTA LA VISTA, BABY

Explanations (Thanks Bijan):

DeclareMethod f
        MethodArguments a
        MethodArguments b
        NonVoidMethod
        DeclareInt r
        SetInitialValue 1
        DeclareInt l
        SetInitialValue 1
        WHILE l
                AssignVariable r
                        SetValue r
                        MultiplicationOperator a
                EndAssignVariable
                AssignVariable a
                        SetValue a
                        + 1
                EndAssignVariable
                AssignVariable l
                        SetValue b
                        > a
                EndAssignVariable
        EndWhile
        Return r
EndMethodDeclaration

Answer 3

Python, 30 bytes

f=lambda a,b:a>b or a*f(a+1,b)

Inclusive range. Repeatedly multiplies by and increments the left endpoint, until it is higher than the right endpoint, in which case it's the empty product of 1 (as True).

Answer 4

Minecraft 15w35a+, program size 456 total (see below)

This calculates PI [a,b). Input is given by using these two commands: /scoreboard players set A A {num} and /scoreboard players set B A {num}. Remember to use /scoreboard objectives add A dummy before input.

Scored using: {program size} + ( 2 * {input command} ) + {scoreboard command} = 356 + ( 2 * 33 ) + 34 = 456.

This code corresponds to the following psuedocode:

R = 1
loop:
  R *= A
  A += 1
  if A == B:
    print R
    end program

Download the world here.

Answer 5

TI-BASIC, 9 bytes

Input A
prod(randIntNoRep(A,Ans

Takes one number from Ans and another from a prompt.

Also 9 bytes, taking input as a list from Ans:

prod(randIntNoRep(min(Ans),max(Ans

Answer 6

Python 2, 44 38 bytes

lambda l:reduce(int.__mul__,range(*l))

Pretty much the obvious anonymous function answer.

EDIT: Thanks to xnor for saving 6 bytes with some features I didn't know.

Answer 7

Pyth, 5 bytes

*FrQE

Pyth doesn't have product, so we reduce * over the range.

Uses exclusive range.

Answer 8

R, 22 bytes

function(a,b)prod(a:b)

Answer 9

Mathematica, 15 bytes

1##&@@Range@##&

A shorter solution that only works for non-negative integers:

#2!/(#-1)!&

Answer 10

JavaScript (ES6), 34 bytes

(a,b)=>eval("for(c=a;a<b;)c*=++a")

Sometimes the simplest answer is the best! Just a for loop inside eval. Inclusive range.

Answer 11

Japt, 7 bytes

Easy challenges like this are always fun. :)

UoV r*1

Try it online!

Explanation

UoV r*1  // Implicit: U = first input, V = second input
UoV      // Generate range [U,V).
    r*1  // Reduce by multiplication, starting at 1.

Wow, this seems pathetic compared to the other answers so far. I need to work on Japt some more...

Answer 12

Seriously, 4 bytes

,ixπ

,         Read list [a,b] from stdin
 i        Flatten it to a b
  x       Pop a,b, push range(a,b)
   π      Pop the list and push its product.

Hex Dump:

2c6978e3

Try it online

Answer 13

Prolog, 45 bytes

Code:

p(A,B,C):-A=B,C=A;D is A+1,p(D,B,E),C is A*E.

Explained:

p(A,B,C):-A=B,      % A is unifiable with B
          C=A       % Unify C with A
          ;         % OR
          D is A+1, % D is the next number in the range
          p(D,B,E), % Recurse on the range after the first element
          C is A*E. % The result C is the product of the first element and the result 
                      of the recursion

Example:

p(5,10,X).
X = 151200

p(-4,-1,X).
X = 24

Answer 14

Octave, 15 bytes

@(a,b)prod(a:b)

Straightforward. Uses the inclusive range.

Answer 15

CJam, 6 19 18 10 bytes

Thanks to Dennis and RetoKoradi for help with golfing!

q~1$-,f+:*

Try it online

Takes input as a b. Calculates PI [a,b).

Note: this program is 6 bytes long, and only works if a and b are positive.

q~,>:*

Try it online

Takes input as a b. Calculates PI [a,b).

Answer 16

Haskell, 19 17 bytes

a#b=product[a..b]

Usage example: 2#5-> 120.

Answer 17

Julia, 16 bytes

f(a,b)=prod(a:b)

Note: if the range object a:b (which is literally stored as a start value and a stop value, and internally includes a "increment by 1 on each step" value) is permitted as the input, then just 4 bytes are required: prod.

Answer 18

C, 32 bytes

For [a,b):

f(a,b){return a-b?a*f(a+1,b):1;}

For [a,b] (On Katenkyo's suggestions, 32 bytes again) :

f(a,b){return a<b?a*f(a+1,b):b;}

Answer 19

Bash + GNU utilities, 13

seq -s* $@|bc

Assumes there are no files in the current directory whose names start with -s. Start and end (inclusive) are passed as command-line parameters.

This simply produces the sequence from start to end, separated by *, then pipes to bc for arithmetic evaluation.

Answer 20

JavaScript (ES6), 22 bytes

I can't believe none of us JS golfers thought to use recursion...

a=>F=b=>a-b?b*F(b-1):a

Assign to a variable with e.g. var q = a=>F=b=>a-b?b*F(b-1):a, then call like q(2)(5).

Answer 21

Brachylog, 3 bytes

⟦₃×

Try it online!

Input is passed as [A,B]. The range is exclusive of B, but could be made inclusive by replacing the ₃ with ₂.

Answer 22

MATL, 4 bytes

Inclusive Range

2$:p

Try it online!

Explanation

2$: % Implicitly grab two input arguments and create the array input1:input2
p   % Take the product of all array elements

Thanks to @Don Muesli for helping me get the hang of this whole MATL thing.

Answer 23

Jolf, 4 bytes

Try it here!

OrjJ
  jJ two inputs
 r   range between them [j,J)
O    product

Answer 24

Ruby, 22 bytes

->i,n{(i..n).reduce:*}

Ungolfed:

-> i,n {
  (i..n).reduce:* # Product of a range
}

Usage:

->i,n{(i..n).reduce:*}[5,10]
=> 151200

Answer 25

PowerShell, 30 Bytes

param($a,$b)$a..$b-join'*'|iex

Takes input as two integers, creates a range with .., then -joins that with asterisks, pipes it into Invoke-Expression (similar to eval). The range operator in PowerShell is inclusive.

Pretty competitive with non-golfing languages.

Answer 26

J, 8 bytes

[:%/!@<:

Usage

>> f =: [:%/!@<:
>> f 10 5
<< 15120

where >> is STDIN and << is STDOUT.

Explanation

It computes ∏[a,b] as (b-1)!/(a-1)!.

minus_one =: <:
factorial =: !
of        =: @
monadic   =: [:
division  =: %/
f =: monadic division factorial of minus_one

Previous 13-byte version

Written when I had no idea what J even is :p

*/(}.[:>:i.)/

Usage:

   */(}.[:>:i.)/ 5 10
30240

Explanation:

*/            NB. multiply over
  (
   }.         NB. remove [the first x items] from
     [:>:     NB. increment all of
         i.   NB. the numbers from 0 to [y-1]
           )
            / NB. insert the above code into the following numbers

Detailed explanation:

i.10 would produce 0 1 2 3 4 5 6 7 8 9

>:i.10 would make it 1 2 3 4 5 6 6 7 8 9 10

the [: is used to make the ">:" take only one argument (a monad)
because if it takes two arguments, it is a different function.
so [:>:i.10 becomes 1 2 3 4 5 6 7 8 9 10

}. means take away the first [x] items from the following list,
so 5}.1 2 3 4 5 6 7 8 9 10 becomes 6 7 8 9 10

the two slashes "/" in the code are actually the same
for example, */6 7 8 9 10 becomes 6*7*8*9*10

Answer 27

APL (Dyalog Extended), 8 3 bytes^SBCS

×/…

Try it online!

… range

×/ multiplication across

This is an "atop" so a(×/…)b is ×/a…b.

Answer 28

R, 21 bytes

Thanks to Dominic van Essen for helping me brainstorm input methods.

prod((a=scan()):a[2])

Uses inclusive range. Try it online!

Explanation

      a=scan()         Read the two inputs as a vector and assign it to a
     (        ):       Use a as the lower end of a range (R interprets this as "use the
                        first element of the vector" by default)
                a[2]   Use the second element of a as the upper end of the range
prod(               )  Take the product of all numbers in the range

Answer 29

Desmos, 19 bytes

f(a,b)=∏_{n=a}^bn

Try it on Desmos!

Answer 30

05AB1E, 2 bytes

Code:

ŸP

Explanation:

Ÿ   # Inclusive range [input, ..., input]
 P  # Total product of the list
    # Implicit printing top of the stack