Elm - String
A sequence of Unicode characters is called a String. In Elm, strings are enclosed in "" double quotes. A String is a chunk of text as shown below.
> "Howcodex"
"Howcodex" : String
> location = "Hyderabad" --variable
"Hyderabad" : String
> location
"Hyderabad" : String
>
String Functions
Some common functions that can be used to query or manipulate string values are given below. Use REPL to try the examples given below.
| Sr. No |
Method |
Description |
| 1 |
isEmpty : String -> Bool |
checks string is empty |
| 2 |
reverse : String -> String |
reverses a input string |
| 3 |
length : String -> Int |
returns an integer length |
| 4 |
append :String -> String -> String |
appends two string and returns a new string |
| 5 |
append :String -> Sconcat : List String -> String |
appends a list of strings and returns a new string |
| 6 |
split : String -> String -> List String |
splits an input string using a given separator, returns a string list |
| 7 |
slice : Int -> Int -> String -> String |
returns a substring given a start , end index and input string |
| 8 |
contains : String -> String -> Bool |
returns true if second string contains the first one |
| 9 |
toInt : String -> Result.Result String Int |
parses a String to Integer |
| 10 |
toInt : String -> Result.Result String Int |
parses a String to Integer |
| 11 |
toFloat : String -> Result.Result String Float |
parses a String to float |
| 12 |
fromChar : Char -> String |
creates a string from a given character. |
| 13 |
toList : String -> List Char |
converts string to list of characters |
| 14 |
fromList : List Char -> String |
converts a list of characters into a String |
| 15 |
toUpper : String -> String |
converts input string to upper case |
| 16 |
trim : String -> String |
gets rid of whitespace on both sides of a string. |
| 17 |
filter : (Char -> Bool) -> String -> String |
filters set of characters from input string |
| 18 |
map : (Char -> Char) -> String -> String |
transforms every character in an input string |
isEmpty
This function can be used to determine if a string is empty. This function returns True if the supplied String is empty.
Syntax
String.isEmpty String_value
To check the signature of function, type the following in elm REPL −
> String.isEmpty
<function> : String -> Bool
Signature of the function shows Bool as return type and input type as String −
Illustration
> String.isEmpty ""
True : Bool
> String.isEmpty "Howcodex"
False : Bool
> location = "Hyderabad"
"Hyderabad" : String
> String.isEmpty location
False : Bool
reverse
This function reverses a string.
Syntax
String.reverse String_value
To check the signature of function, type the following in elm REPL −
> String.reverse
<function> : String -> String
Signature of the function shows String as return type and input type as String −
Illustration
> String.reverse "Howcodex"
"tnioPslairotuT" : String
length
This function returns the length of a string.
Syntax
String.length String_value
To check the signature of function, type the following in elm REPL −
> String.length
<function-> : String -> Int
Signature of the function shows Int as return type and input type as String.
Illustration
> String.length "Mohtashim"
9 : Int
append
This function returns a new string by appending two strings.
Syntax
String.append String_value1 String_value2
To check the signature of function, type the following in elm REPL −
> String.append
<function-> : String -> String -> String
Signature of shows two String input parameters and one String output parameter
Illustration
> String.append "Tutorials" "Point"
Howcodex : String
concat
This function returns a new string by concatenating many strings into one.
Syntax
String.concat [String1,String2,String3]
To check the signature of function, type the following in elm REPL −
> String.concat
<function> : List String -> String
Signature of shows a List of String input parameter and String return type
Illustration
> String.concat ["Hello","Tutorials","Point"]
HelloHowcodex : String
split
This function splits a string using a given separator.
Syntax
String.split string_seperator String_value
To check the signature of function, type the following in elm REPL −
> String.split
<function> : String -> String -> List String
Signature of shows two input String parameters and output as a list of string type.
Illustration
> String.split "," "Hello,Tutorials,Point"
["Hello","Tutorials","Point"] : List String
slice
This function returns a substring given a start and end index. Negative indexes are taken starting from the end of the list. The value of the index starts from zero.
Syntax
String.slice start_index end_index String_value
To check the signature of function, type the following in elm REPL −
> String.slice
<function> : Int -> Int -> String -> String
Signature of shows three input parameter and one return type.
Illustration
> String.slice 0 13 "Howcodex"
"TutorialsPoin" : String
contains
This function returns a True if the second string contains the first one.
Syntax
String.contains string1 string2
To check the signature of function, type the following in elm REPL −
> String.contains
<function> : String -> String -> Bool
Signature of shows bool return type and two input parameters
Illustration
> String.contains "Point" "Howcodex"
True : Bool
toInt
This function converts a string into an int.
Syntax
String.toInt string_value
To check the signature of function, type the following in elm REPL −
> String.toInt
<function> : String -> Result.Result String Int
Since toInt can return error, the return type is Result, which is String or Int.
Illustration
> String.toInt "20"
Ok 20 : Result.Result String Int
> String.toInt "abc"
Err "could not convert string 'abc' to an Int" : Result.Result String Int
toFloat
This function converts a string into a float.
Syntax
String.toFloat string_value
To check the signature of function, type the following in elm REPL −
> String.toFloat
<function> : String -> Result.Result String Float
Since toFloat can return error, the return type is Result, which is String or Float.
Illustration
> String.toFloat "20.50"
Ok 20.5 : Result.Result String Float
> String.toFloat "abc"
Err "could not convert string 'abc' to a Float" : Result.Result String Float
fromChar
This function creates a string from a given character.
Syntax
String.fromChar character_value
To check the signature of function type following in elm REPL −
> String.fromChar
<function> : Char -> String
The signature shows String as return type and input as Char type
Illustration
> String.fromChar 'c'
"c" : String
toList
This function converts a string to a list of characters.
Syntax
String.toList string_value
To check the signature of function, type the following in elm REPL −
> String.toList
<function> : String -> List Char
The signatures shows function returns a list of characters and takes input a string.
Illustration
> String.toList "howcodex"
['t','u','t','o','r','i','a','l','s','p','o','i','n','t'] : List Char
fromList
This function converts a list of characters into a String.
Syntax
String.fromList list_of_characters
To check the signature of function, type the following in elm REPL −
> String.fromList
<function> : List Char -> String
The signatures shows function returns a list of characters and takes input a string.
Illustration
> String.fromList ['h','e','l','l','o']
"hello" : String
toUpper
This function converts a string to all upper case.
Syntax
String.toUpper String_value
To check the signature of function, type the following in elm REPL −
> String.toUpper
<function> : String -> String
Illustration
> String.toUpper "hello"
"HELLO" : String
toLower
This function converts a string to all lower case.
Syntax
String.toLower String_value
To check the signature of function, type the following in elm REPL −
> String.toLower
<function> : String -> String
Illustration
> String.toLower "AbCd"
"abcd" : String
trim
This function gets rid of whitespace on both sides of a string.
Syntax
String.trim String_value
To check the signature of function, type the following in elm REPL −
> String.trim
<function> : String -> String
Illustration
> String.trim "howcodex "
"howcodex" : String
filter
This function filters a set of characters from input String. Keep only the characters that pass the test.
Syntax
String.filter test_function string_value
To check the signature of function, type the following in elm REPL −
> String.filter
<function> : (Char -> Bool) -> String -> String
The signature shows filter takes two input parameters and returns a String. The first parameter is a function, which has input Char and returns Bool.
Illustration
In the example, we are passing Char.isUpper as parameter to filter method; it returns all upper-case characters as shown below.
> import Char
> String.filter Char.isUpper "abcDEF"
"DEF" : String
map
This function takes a String and transforms every character in a string.
Syntax
String.filter mapping_function string_value
To check the signature of function, type the following in elm REPL −
> String.map
<function> : (Char -> Char) -> String -> String
Illustration
The following example replaces the character o with @ −
> String.map (\c -> if c == 'o' then '@' else c) "Howcodex"
"Tut@rialsP@int" : String
