Question

I write program for searching in index list of tuple by binary search I write and work fine

superBubble::(Ord t) =>[[t]]->[[t]]
superBubble a=map bubbleSort a
combining::[BookInfo]->[Int]
combining books= bubbleSort(map index books)  
 binsearch :: [Int] -> Int -> Int -> Int -> Int -- list, value, low, high, return int
 binsearch xs value low high
  | high < low       = -1
  | xs!!mid > value  = binsearch xs value low (mid-1)
  | xs!!mid < value  = binsearch xs value (mid+1) high
  | otherwise        = mid
   where
   mid = low + ((high - low) `div` 2)
  final::[BookInfo]->Int->Int->Int->Int 
  final vs key s r= binsearch concat( combining vs) key s r

and the other functions work propaply but when i add it to the hole give me an error

the error is unexcpted ‘|’ the first one but why?

Answer 1

The lines from binsearch :: are indented one more space than the lines before it. Unindent each of those lines by one space.

Additionally, the lines from final:: onwards are indented two more spaces than the initial lines. Unindent each of these lines by two spaces.

Finally, as Daniel points out, you have a -< in your final:: line, instead of a ->. (Which you have now corrected in your posted code, thus confusing anyone who looks at this question in future.)

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Correct code:

superBubble::(Ord t) =>[[t]]->[[t]]
superBubble a=map bubbleSort a
combining::[BookInfo]->[Int]
combining books= bubbleSort(map index books)  
binsearch :: [Int] -> Int -> Int -> Int -> Int -- list, value, low, high, return int
binsearch xs value low high
 | high < low       = -1
 | xs!!mid > value  = binsearch xs value low (mid-1)
 | xs!!mid < value  = binsearch xs value (mid+1) high
 | otherwise        = mid
  where
  mid = low + ((high - low) `div` 2)
final::[BookInfo]->Int->Int->Int->Int 
final vs key s r= binsearch concat( combining vs) key s r

(And you need to include definitions of bubbleSort, BookInfo and index as well.)

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Why is your indentation an error?

Because it makes binsearch look as if it is part of the value of combining, instead of a separate function. The first | is the first character that can’t possibly be part of an expression.