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I have a problem with one code and hope that you can help me with that.

I have a list which looks like the following

List = {a, b, c, d, e}

the desired result is a new list with

{a, a*b, a*b*c, a*b*c*d, a*b*c*d*e}

Thanks in advance

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  • $\begingroup$ Like Fold[Times, 1, list]? Also List is a built-in symbol, so don't use it as a variable. Stick to variables starting with lower-case letters. $\endgroup$
    – J. M.'s missing motivation ♦
    Commented Jan 31, 2020 at 16:11
  • $\begingroup$ @J.M. your command returns abcde. The OP asks that this is the final element of the new list created by multiplication of the elements of the original ones. $\endgroup$
    – user49048
    Commented Jan 31, 2020 at 16:16
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    $\begingroup$ Oops, that should be FoldList[] and not Fold[]; thanks @Darth! $\endgroup$
    – J. M.'s missing motivation ♦
    Commented Jan 31, 2020 at 16:17
  • $\begingroup$ @J.M.isinlimbo that's the trick, yes. I tried to do it using Nest, NestList and failed spectacularly :-) $\endgroup$
    – user49048
    Commented Jan 31, 2020 at 16:18
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    $\begingroup$ FoldList[Times, {a, b, c, d,e}] $\endgroup$
    – A little mouse on the pampas
    Commented Feb 1, 2020 at 5:25

5 Answers 5

Reset to default
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Accumulate takes the sum of the terms: this can be changed to the product of by changing the Plus to Times:

 list = {a, b, c, d, e};
 Accumulate@list /. Plus -> Times
 {a, a b, a b c, a b c d, a b c d e}
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    $\begingroup$ Alternatively Block[{Plus = Times}, Accumulate@list] if you don't want to use replacements. $\endgroup$
    – NonDairyNeutrino
    Commented Feb 1, 2020 at 5:58
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Another way:

list = {a, b, c, d, e};
E^Accumulate[Log[list]]

Since Accumulate equals Rest[FoldList[Plus,0,list]] , So Foldlist also works.

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Another:

ReplaceList[{a, b, c, d,e}, { x__,___} :> Times@x ]

{a, a b, a b c, a b c d, a b c d e}

Comparing:

ReplaceList[{a, b, c, d,e}, { x__,___} :> Times@x ] == FoldList[Times] @ {a, b, c, d,e}

True

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Here's an operator version of @JM's suggestion in the comments:

list = {a, b, c, d, e};

FoldList[Times] @ list

{a, a b, a b c, a b c d, a b c d e}

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$\begingroup$ 
list = {a, b, c, d, e};

Using TimesBy

Module[{a = 1}, a *= # & /@ list]

{a, a b, a b c, a b c d, a b c d e}

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