Erlang - Strings
A String literal is constructed in Erlang by enclosing the string text in quotations. Strings in Erlang need to be constructed using the double quotation marks such as “Hello World”.
Following is an example of the usage of strings in Erlang −
Example
-module(helloworld).
-export([start/0]).
start() ->
Str1 = "This is a string",
io:fwrite("~p~n",[Str1]).
The above example creates a string variable called Str1. The string “This is a string” is assigned to the variable and displayed accordingly.
The output of the above program will be −
Output
“This is a string”
Next, we will discuss the various operations available for Strings. Note that for string operations, you need to include the string library as well.
| Sr.No |
String Methods & Description |
| 1 |
len
The method returns the length of a particular string.
|
| 2 |
equal
The method returns a Boolean value on whether one string is equal to another.
|
| 3 |
concat
The method concats 2 strings and returns the concatenated string.
|
| 4 |
chr
The method returns the index position of a character in a string.
|
| 5 |
str
The method returns the index position of a sub string in a string.
|
| 6 |
substr
The method returns the sub string from the original string based on the starting position and number of characters from the starting position.
|
| 7 |
left
The method returns the sub string from the original string based on the starting position and number of characters from the starting position.
|
left with trailing character
The method returns the sub string from the left of the string based on the number of characters. But with the option to include a trailing character if the number is greater than the length of the string.
Syntax
left(str1,number,$character)
Parameters
str1 − This is the string from which the sub string needs to be extracted.
Number − This is the number of characters which need to be present in the substring.
$Character − The character to include as the trailing character.
Return Value
Returns the sub string from the original string based on the left hand side of the string and the number.
For example
-module(helloworld).
-import(string,[left/3]).
-export([start/0]).
start() ->
Str1 = "hello",
Str2 = left(Str1,10,$.),
io:fwrite("~p~n",[Str2]).
Output
When we run the above program, we will get the following result.
"hello....."
right
The method returns the sub string from the right of the string based on the number of characters.
Syntax
right(str1,number)
Parameters
Return Value
Returns the substring from the original string based on the right hand side of the string and the number.
For example
-module(helloworld).
-import(string,[right/2]).
-export([start/0]).
start() ->
Str1 = "hello World",
Str2 = right(Str1,2),
io:fwrite("~p~n",[Str2]).
Output
When we run the above program, we will get the following result.
“ld”
right with trailing character
The method returns the substring from the right of the string based on the number of characters. But with the option to include a trailing character if the number is greater than the length of the string.
Syntax
right(str1,number,$character)
Parameters
str1 − This is the string from which the sub string needs to be extracted.
Number − This is the number of characters which need to be present in the substring.
$Character − The character to include as the trailing character.
Return Value
Returns the sub string from the original string based on the right hand side of the string and the number.
For example
-module(helloworld).
-import(string,[right/3]).
-export([start/0]).
start() ->
Str1 = "hello",
Str2 = right(Str1,10,$.),
io:fwrite("~p~n",[Str2]).
Output
When we run the above program, we will get the following result.
".....hello"
to_lower
The method returns the string in lower case.
Syntax
to_lower(str1)
Parameters
Return Value
Returns the string in lower case.
For example
-module(helloworld).
-import(string,[to_lower/1]).
-export([start/0]).
start() ->
Str1 = "HELLO WORLD",
Str2 = to_lower(Str1),
io:fwrite("~p~n",[Str2]).
Output
When we run the above program, we will get the following result.
"hello world"
to_upper
The method returns the string in upper case.
Syntax
to_upper(str1)
Parameters
For example
-module(helloworld).
-import(string,[to_upper/1]).
-export([start/0]).
start() ->
Str1 = "hello world",
Str2 = to_upper(Str1),
io:fwrite("~p~n",[Str2]).
Output
When we run the above program, we will get the following result.
"HELLO WORLD"
sub_string
Returns a substring of String, starting at the position Start to the end of the string, or to and including the Stop position.
Syntax
sub_string(str1,start,stop)
Parameters
str1 − This is the string from which the sub string needs to be returned.
start − This is the start position of the sub string
stop − This is the stop position of the sub string
Return Value
Returns a substring of String, starting at the position Start to the end of the string, or to and including the Stop position.
For example
-module(helloworld).
-import(string,[sub_string/3]).
-export([start/0]).
start() ->
Str1 = "hello world",
Str2 = sub_string(Str1,1,5),
io:fwrite("~p~n",[Str2]).
Output
When we run the above program, we will get the following result.
"hello"
