FPPrac.Prelude

The Prelude defines the Number type (which is like Amanda's num type), and hides the intricacies of Haskell's Type Classes from new users when dealing with number. Also defines corresponding Prelude functions that use this new Number type.

Documentation

module Prelude

data Number

Combined integral and floating number type

Instances

Enum Number

Eq Number

Floating Number

Fractional Number

Integral Number

Num Number

Ord Number

Read Number

Real Number

RealFrac Number

Show Number

ord :: Char -> Number

chr :: Number -> Char

length :: [a] -> Number

O(n). length returns the length of a finite list as a Number.

(!!) :: [a] -> Number -> a

List index (subscript) operator, starting from 0.

replicate :: Number -> a -> [a]

replicate n x is a list of length n with x the value of every element.

Fails when n is not an integral number

take :: Number -> [a] -> [a]

take n, applied to a list xs, returns the prefix of xs of length n, or xs itself if n > length xs:

 take 5 "Hello World!" == "Hello"
 take 3 [1,2,3,4,5] == [1,2,3]
 take 3 [1,2] == [1,2]
 take 3 [] == []
 take (-1) [1,2] == []
 take 0 [1,2] == []

Fails when n is not an integral number

drop :: Number -> [a] -> [a]

drop n xs returns the suffix of xs after the first n elements, or [] if n > length xs:

 drop 6 "Hello World!" == "World!"
 drop 3 [1,2,3,4,5] == [4,5]
 drop 3 [1,2] == []
 drop 3 [] == []
 drop (-1) [1,2] == [1,2]
 drop 0 [1,2] == [1,2]

Fails when n is not an integral number

splitAt :: Number -> [a] -> ([a], [a])

splitAt n xs returns a tuple where first element is xs prefix of length n and second element is the remainder of the list:

 splitAt 6 "Hello World!" == ("Hello ","World!")
 splitAt 3 [1,2,3,4,5] == ([1,2,3],[4,5])
 splitAt 1 [1,2,3] == ([1],[2,3])
 splitAt 3 [1,2,3] == ([1,2,3],[])
 splitAt 4 [1,2,3] == ([1,2,3],[])
 splitAt 0 [1,2,3] == ([],[1,2,3])
 splitAt (-1) [1,2,3] == ([],[1,2,3])

It is equivalent to (take n xs, drop n xs) when n is not _|_ (splitAt _|_ xs = _|_).

Fails when n is not an integral number