Haskell: lexical error in string/character literal at character 'i'

haskell recursion lexical
Gus picture Gus · Feb 5, 2011 · Viewed 14.7k times · Source

I'm fairly new to Haskell programming and I'm having trouble understanding why I'm receiving this error in my code.

My problem is as follows: Any positive integer i can be expressed as i = 2^n*k, where k is odd, that is, as a power of 2 times an odd number. We call n the exponent of 2 in i. For example, the exponent of 2 in 40 is 3 (because 40 = 2^3*5) whereas the exponent of 2 in 42 is 1. If i itself is odd, then n is zero. If, on the other hand, i is even, that means it can be divided by 2. Write a function exponentOfTwo for finding the exponent of 2 in its argument.

I understand the psuedocode and it seems fairly simple: recursively divide i by 2 until result is odd, the number of times the division happens is n

here is my code (line 31-32):

exponentOfTwo :: Int -> Int  
exponentOfTwo i = if odd i then 0 else 1 + exponentOfTwo (i 'div' 2)

I'm receiving the error "lexical error in string/character literal at character 'i'" on line 32 column 62.

I've tried searching for a solution to this error everywhere and so far I've had no luck.

Answer

user395760 picture user395760 · Feb 5, 2011

To use a function in infix for, surround it with backticks (`), not with single quotes ('). The latter are for character literals, which, well are only one character long.

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