Haskell functions 20190405 1832 1

haskell/functions/php_explode.hs

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+
+-- A function which works as PHP Explode 
+-- https://www.php.net/manual/es/function.explode.php
+
+-- Lists Slice 
+-- Arg1: Start Index 
+-- Arg2: End Index 
+-- Arg3: Input List 
+-- Return: Output List 
+slice :: Int -> Int -> [a] -> [a]
+slice from to xs = take (to - from + 1) (drop from xs)
+
+
+-- Is Space 
+-- Arg1: String 
+-- Arg2: Position 
+-- Return: Bool representing if i-th char is a space 
+is_space :: String -> Int -> Bool 
+is_space s i = (s!!i == ' ')
+
+-- Is Char 
+-- Arg1: String 
+-- Arg2: Position 
+-- Return: Bool representing if i-th char is equal to query char 
+is_char :: String -> Char -> Int -> Bool 
+is_char s c i = (s!!i == c)
+
+
+
+-- Builds a List of N elements each representing the position of a space in the input string 
+-- Arg1: Input String 
+-- Return: List of Int representing the positions of space in the string 
+get_spaces :: String -> [Int]
+get_spaces s = [i | i <- [0 .. ((length s)-1)], is_space s i]
+
+-- Builds a list of N elements each representing the position of the given chan in the input string 
+find_separators :: String -> Char -> [Int]
+find_separators s c = [ i | i <- [ 0 .. ((length s)-1) ], is_char s c i ]
+
+-- Equivalen to PHP Explode so breaks the input string into a list of substring according to given separator char 
+explode :: String -> Char -> [String]
+explode s c 
+  | d == [] = [s]
+  | otherwise = initial ++ [ slice ((d!!(i-1))+1) ((d!!i)-1) s | i <- [1 .. ((length d)-1)] ] ++ final 
+  where 
+  d = find_separators s c 
+  initial = [(slice 0 ((d!!0)-1) s)]
+  final = [(slice ((d!!((length d)-1))+1) ((length s)-1) s)]
+
+
+
+-- Tests 
+main = do 
+  let a = "Hello this is a test of a function"
+  let b = "Test"
+  print (explode a ' ')
+  print (explode b ' ')
+
+
+

haskell/functions/readme.md

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+
+# Overview 
+
+Some Convenient Haskell Functions developed mostly as exercises 
+
+# String Manipulation 
+
+## PHP Explode 
+
+Build a function that as [PHP Explode](https://www.php.net/manual/es/function.explode.php) takes a string and breaks it up into a list of substring according to given separator char 
+- [Sol](php_explode.hs)
+
+
+Work in progress 
+
+
+
+
+
+
+