02-grammar-and-types.md

Grammar and Data Types

Basics

Swahili borrows its syntax from Javascript, Python and Ruby. Like Javascript, Swahili is case sensitive. as such the declarations below are different variables.

wacha b = 5
wacha B = 3

Comments

Swahili uses // for single line comments and /* */ for multiline comments

// This is a single line comment

/*  This
    is
    a
    Multiline
    Comment
*/

Variables

Variables are used as symbolic names for values within the program. The names of variables, called identifiers must begin with either an underscore ( _ ), or an alphabetic character in either upper or lower case. Subsequent characters can be alphanumeric or an underscore. Hence:

wacha _jina = "John"  // valid
wacha Jina = "John"   // valid
wacha jina = "John"   // valid
wacha 0_jina = "John" // invalid

Swahili is case sensitive, hence, Neno and neno are different variables.

You cannot use Swahli keywords as variable names.

wacha kweli = uwongo // will raise an error because kweli is a Swahili keyword

Declaring Variables

To declare a variable, we use the keyword wacha, followed by the identifier name and an initialization. You have to initialize your variables when you declare them. If you want a variable to be empty on declaration you intitalize it to null (tupu).

wacha jina        // will raise an error
wacha jina = ""   // is valid
wacha jina = tupu // initializes jina to null

• An attempt to access an undeclared variable results in a Runtime error.
• You can not perform basic arithmetic and boolean operations on variables with a null value.

Variable Scope

Variables you declare within a global scope (outside of any function) cannot be redeclared, ie,

wacha x = 3
wacha x = 5 // this line will raise an error
x = 5       // this will not raise an error

• Variables declared inside a function block are only available for that block. For instance:

  wacha a = "Outside block"
  shughuli block_example() {
    wacha a = "Inside Block"
    andika(a)
  }
  block_example() // => "Inside Block"
  andika(a)       // => "Outside block"

Data Structures and Data types

• There are 8 Data structures and Types in Swahili.
  1. Boolean Hali: kweli that represents true and uwongo that represents false
  2. null tupu: Denotes a null value
  3. Number Nambari: Could be both Integers and floats. For example 42 or 3.14159
  4. Strings Jina: A sequence of characters that represents a text value. For example Habari
  5. Lists Orodha: An ordered collection of items. Can hold multiple data types: for example [1,2,3] or [1, "orodha", kweli]
  6. Regular Expressions RegEx: These are patterns used to match character combinations in strings.
  7. Date Tarehe: Used to represent a date object.
  8. Object Kamusi: Works like a dictionary by storing items as key/value pairs

List literals

• A list literal is a collection of zero or more expressions, each of which represents a list element enclosed in square brackets. The length of a list is set to the number of arguments specified.
• The following creates a list of vinywaji

wacha vinywaji = ["chai", "kahawa ya Uhabeshi", "Kahawa ya Kenya" ]

• Lists in Swahili are zero based, which means that the first element has the index of zero.

Acessing Elements in a list

• Unlike most languages access a specific element in an array we put the index after a forward slash. For example

  wacha vinywaji = ["chai", "kahawa ya Uhabeshi", "Kahawa ya Kenya" ]
  andika(vinywaji/0) // => "chai"
  andika(vinywaji/2) // => "Kahawa ya Kenya"

Appending elements to a list

• To append an element to the end of a list we use the plus sign(+) followed by the element we want to add. For Example

vinywaji = vinywaji + "soda"
andika(vinywaji) // => ["chai", "kahawa ya Uhabeshi", "Kahawa ya Kenya", "soda" ]

Deleting elements in a list

• To delete an element in a list we use the - followed by the index of the element. For Example:

vinywaji = vinywaji - 3
andika(vinywaji) // => ["chai", "kahawa ya Uhabeshi", "Kahawa ya Kenya" ]

Concatenation of 2 lists

• We can combine 2 lists into one using an asterisk (*)
• For Example:

  wacha vyakula = ["maandazi", "wali", "mahamri"]
  wacha vyakula_vinywaji = vinywaji * vyakula
  andika(vyakula_vinywaji) // => ["chai", "kahawa ya Uhabeshi", "Kahawa ya Kenya", "maandazi", "wali", "mahamri"]

Boolean literals

• The boolean type has 2 literal values: kweli and uwongo

Numeric literals

• The Number type contains both floats and integers.
• Swahili deals only with numbers in base ten, ie, decimal number system
• Examples of numeric literals are: 1,100, 3.14159, 2.71828

String literals

• A string literal is zero or more characters enclosed in double(" ") quotation marks. Swahili does not support use of single quotation marks to denote strings, hence andika('Habari Dunia') is invalid but andika("Habari Dunia") is valid.

Special Characters

• In addition to ordinary characters you can also add special characters to strings.
• For Example

  wacha a = "habari \n yako"

• The charaters \n add a new line. The list of special characters is shown below

Character	Meaning
\n	New line
\t	Tab space
"	Double quote

Regular Expressions (RegEx)

• These are patterns used to match character combinations in strings.
• To declare a RegExp we use the RegEx() function. The function takes in 2 arguments; A RegEx pattern and a RegEx flag. RegEx("pattern", "flag")
• For Example:

  wacha a = RegEx("ab+c", "g")
  andika(a) // => /ab+c/g

Dates

• Used to represent a date object. The keyword used to initialize a date is Tarehe().

  wacha s = Tarehe()

• For more information, check here and here

Object Literals

An object literal is a list of zero or more pairs of property names and associated values of an object, enclosed in curly braces ({}).

For example:

  wacha mtu = {
    jina: "Wendo",
    umri: 21,
    urefu : 180
  }

This then allows us to get specific values by checking their keys. For instance mtu.jina would return "Wendo"