thp/doc-generator/markdown/en/stdlib/latest/prelude/String.md

String

A collection of UTF-16 characters.

---

Overview

Strings are a primitive datatype that contain a series of UTF-16 encoded characters.

To create a string use double quotes:

val greeting = "Hello there!"

// With type annotation
Str greeting = "Hello there!"

Misti doesn't allow string creation with single quotes <code>''</code>.

Strings can be concatenated with the plus + operator:

val name = "John"
val greeting = "Hello"

val fullGreeting = greeting + " " + name + "!"
//  fullGreeting = "Hello John!"

In the future, the language will support string concatenation and multi-line strings.

String comparison

To check if two strings are the same use the equal-to == operator.

"Hello" == "Hello"  //: true
"Hello" == "hello"  //: false

To check if two strings are different use the not-equal-to != operator.

"abc" != "123"  //: true
"xyz" != "xyz"  //: false

Comparing strings with <, <=, > & >= will compare each character of the string, based on the UTF-16 value.

"a" < "b"     //: true
"a" < "A"     //: false

"aab" > "aac" //: false
"aab" < "aac" //: true

Automatic String conversion

Misti does not automatically convert other datatypes to String.

val sentence = "My age is: " + 20  // This will throw an error
//                           ^
// Cannot concatenate a String and a Number.

To do so use the method .toStr() to explicitly convert to String.

val sentence = "My age is: " + 20.toStr()  // ok

In the future, string interpolation will coerce datatypes into strings.

Escape characters

Misti supports the following escape characters:

• \"

• \\

• \n

• \r

• \t

• \b

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API

Prelude's Str contains methods and functions created for their usage within Misti.

To access the underlying JavaScript methods, use the js.String module.

Constructor

class String[T](T value)
where T -> Printable

Creates a string from value, by calling its toStr method.

Parameters

• T value: Any value that implements Printable, and therefore has a toStr method.

Examples

val age = String(20)  //: "20"
val condition = String(false) //: "false"
val numbers = Array(1, 2, 3) |> String //: "1,2,3"

Properties

length

Num length

Returns the number of UTF-16 code units in the string.

Example

val name = "John"
name.length        //: 4

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Methods

charAt

fun charAt(Num position) -> Str?

Returns the UTF-16 code unit located at position.

Parameters

• Num position: An integer between 0 and the string's length - 1.

Return

• Str?: The character at position, or None if it's invalid

Description

In a string with length characters, this method returns the character (UTF-16 code point) located at position, if it is true that 0 <= position < length.

If position is out of range, this method will return None.

Examples

val name = "John Doe"

name.charAt(0)  //: Some("J")
name.charAt(1)  //: Some("o")
name.charAt(7)  //: Some("e")

name.charAt(-1) //: None
name.charAt(8)  //: None

If you are sure that the position is valid, you can use the !! operator to get the value directly, instead of a Maybe.

val greeting = "Hello!"

name.charAt(4)!!  //: "o"

concat

fun concat[any T](T... values) -> Str
where T -> Printable

Concatenates the calling string and values, and returns the result as a new Str

Type parameters

• any T: Any datatype that implements Printable

Parameters

• T... values: Zero or more values of type T

Return

• Str: A new string with the values concatenated

Description

concat concatenates the callee, and any arguments passed to it in a new string. The callee is not modified.

If the arguments don't have type Str, they are converted with their toStr method.

Examples

val greeting = "Hello "

greeting.concat("world", "!") //: "Hello world!"
greeting.concat(123)          //: "Hello 123"
greeting.concat(3, 2, 2)      //: "Hello 322"

includes

fun includes(Str searchString, Num pos = 0) -> Bool

Returns whether the current string contains searchString, searching from position pos

Parameters

• Str searchString: The string to search for
• Num pos = 0: The position from where to start searching.

Return

Bool: true if searchString is found, false otherwise

Additional

If searchString is the empty string "" this method returns true.

If pos is negative, the search starts from the first character.

Examples

val loremIpsum = "Lorem ipsum dolor sit amet"

loremIpsum.includes("ipsum")     //: true
loremIpsum.includes("ipsum", 10) //: false
loremIpsum.includes("ipsum", -5) //: true