2 added 53 characters in body
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PlatyPar, 48 bytes

c?1,_p_p\1

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Explanation (pretty simple):

c?        ## if (n != 0)
  1,__p     ## rangeproduct [1..n]
   p    \  ## productelse
        1  ## 1

PlatyPar, 4 bytes

1,_p

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Explanation (pretty simple):

1,_    ## range [1..n]
   p   ## product

PlatyPar, 8 bytes

c?1,_p\1

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Explanation:

c?        ## if (n != 0)
  1,_p     ## product [1..n]
       \  ## else
        1  ## 1
1
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PlatyPar, 4 bytes

1,_p

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Explanation (pretty simple):

1,_    ## range [1..n]
   p   ## product