Question

The problem I have is that I am using isInfixOf on a string below to check whether the word I am looking for is within the string, the below works up to a certain point.

> "world" `isInfixOf` "hello world"
True

but what if it’s part of another word it still returns TRUE as below:

> "wor" `isInfixOf` "hello world"
True

I am trying to find out whether the word passed in is in the string I am looking for but it is not part of another song.

I have tried a lot of methods but I am not sure how I could make sure the word is not part of a another word.

WORDS does not work because it doesn’t strip the string of it’s punc character.

Answer 1

Some regular expression packages could be helpful here.

For example, using regex-prce-builtin.

> :m + Text.Regex.PCRE
> "Hello world" =~ "\\bworld\\b" :: Bool
True
it :: Bool
> "Hello world" =~ "\\bwor\\b" :: Bool
False

\\b stands for \b word boundary, which is used in Perl regular expressions.

So we can define new isInfixOf analogue using (=~).

> let s `isInfixOf_` l = l =~ ("\\b" ++ s ++ "\\b") :: Bool
isInfixOf_ :: RegexLike Regex source1 => [Char] -> source1 -> Bool
> "wor" `isInfixOf_` "Hello world"
False
it :: Bool
> "world" `isInfixOf_` "Hello world"
True
it :: Bool