Convert a list to an integer

Question

How can we convert a list to an integer correctly?

{5, 22, 4, 5} -> 52245?

When I use the command FromDigits in Mathematica

FromDigits[{5, 22, 4, 5}]

The result is incorrect, namely 7245

flinty · Accepted Answer · 2020-06-14T13:05:23.867

11

Here are three ways to do it. The first is the best I think:

FromDigits@Flatten[IntegerDigits /@ {5, 22, 4, 5}]

ToExpression@StringJoin[ToString /@ {5, 22, 4, 5}]

ToExpression@StringJoin@StringCases[Characters@ToString@{5, 22, 4, 5}, DigitCharacter]

edited Jun 14 '20 at 13:05

answered Jun 14 '20 at 12:58

flinty

25,147
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score 10 · Answer 2 · answered Jun 14 '20 at 13:25

10

FromDigits @ ToString @ Row @ {5, 22, 4, 5}

Head[%]

52245
Integer

answered Jun 14 '20 at 13:25

Mr.Wizard

271,378
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587
1,371

score 5 · Answer 3 · answered Jun 14 '20 at 15:18

5

ToExpression@StringJoin@IntegerString[{5, 22, 4, 5}]

52245

ToExpression@StringJoin@IntegerString[{5, 22, 4, 5},#]&/@{2,10,16}

{10110110100101, 52245, 51645}

answered Jun 14 '20 at 15:18

user1066

17,923
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kglr · Answer 4 · 2021-05-25T11:54:53.160

4

{5, 22, 4, 5} ~ StringRiffle ~ "" // FromDigits

edited May 25 '21 at 11:54

answered May 25 '21 at 11:47

kglr

394,356
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477
896

1

Awesome. Never thought of StringRiffle – May 25 '21 at 14:25

score 1 · Answer 5 · answered May 25 '21 at 14:16

1

list = {5, 22, 4, 5};
FromDigits[StringJoin[IntegerString[list]]]

which gives

answered May 25 '21 at 14:16

Convert a list to an integer

5 Answers5