tansang Documentation

Introduction

tansang is

Table of Contents

Hello World

type Main
fn init() {
    Console.puts('hello world')
}

Save this snippet into a file named main.tan. Now do: tansang run main.tan.

Comments

# This is a single line comment.

Functions

type Main
fn init() {
    let a! = [1, 2, 3, 4, 5]
    Console.puts(add(77, 33))
    Console.puts(sub(100, 50))
    Console.puts(sum(a!))
}

fn add(x Int, y Int) Int {
    return x + y
}

fn sub(x Int, y Int) Int {
    return x - y
}

fn sum(a! Array<Int>) <Int>{
    let total! Int = 0
    a.each {
        total.plus!(e) # 

    }    
    return total
}

fn addOne(a! Int) Int {
    a! = a + 1
}



All Function arguments passed by immutable reference.

Returning multiple values

type Main
fn init() {
    let a Int, b Int, c Int
    a, b = foo()
    println(a) # 2
    println(b) # 3
    c, _ = foo() # ignore values using `_`

}

fn foo() (Int, Int) {
    return (2, 3)
}

Variable number of arguments

type Main
fn sum(a Tuple<Int>) Int {
    let total! = 0
    a.each {
        total.plus!(e) # e is each item in a
    }
    return total # redundancy
}

println(sum(1))   //         1
println(sum(2,3)) //         5

Symbol visibility

type Main
getter a
setter b
property c
let a Int, b Int, c Int 
pub fn public_function() {
}

fn private_function() {
}

Instance variable is private by default. To allow access in other type, use getter, setter, property. Functions are private (not exported) by default. To allow other type to use them, prepend pub.

Variables

let name = "Bob",  age = 20
let name String = "Bob", age Int = 20

Variable is always reference.

Mutable variables

let age1! = 20, age2! Int
println(age1)
age2! = age1
Console.puts(age2) 
Console.puts(age1) # error age1 is void after assign to another variable.

Types

Basic type

In tansang everyting is an object and object is types.

tansang provides several literals for creating values of some basic types.

Strings

String name = "Bob"
puts(name.len)
puts(name[0]) // indexing gives a char B, name.charAt(0)
puts(name[1..3]) // slicing gives a string 'ob' name.slice(1, 3)

let s = "hello"
s[0] = 'H' # not allowed

error: cannot assign to s[i] since s is immutable. To mutate String object you can use mutate notation.

let s! = "hello"
s.setAt!(0, 'i') # s[0]! = 'i' 
Console.puts(s) # "iello"

String interpolation

Basic interpolation syntax is pretty simple - use ${expression}. The variable will be converted to a string and embedded into the literal:

let age = 20
Console.puts("My age is ${age + 5}!") # My age is 25!

Format specifiers similar to those in C's printf() are also supported. f, g, x, etc. are optional and specify the output format. The compiler takes care of the storage size, so there is no hd or llu.

let x = 123.4567
Console.puts("x = ${x:4.2f}")
Console.puts('[${x:10}]')       // pad with spaces on the left
Console.puts('[${x.toInt():-10}]') // pad with spaces on the right

String operators

let name = "Bob"
let bobby = name + "by" # + is used to concatenate strings
Console.puts(bobby) # "Bobby"

let s! = "hello "
s! += "world" # `+=` is used to append to a string, s! = s + "world", s.append!("world")
Console.puts(s) // "hello world"
let t! = "hello "
let y! = "world"
t.append(y) # error
t.append!(y)

Numbers

let a = 123 # let a = Int(123)

varible a references the value of 123. By default a will have the type Int. because a is immutable, you can't mutate a.

let a = 123
a += 1 # error
let b! = 125
b! = b + 1 # b.add!(1)

Assigning floating point numbers works the same way:

let f = 1.0 let f1 = Float(3.14)

### Number operators



### Arrays

let nums = [1, 2, 3] println(nums) # "[1, 2, 3]" println(nums[1]) # "2" nums[1] = 5 # error

for mutate

let nums! = [1, 2, 3]
nums[1]! = 5 # nums.setAt!(1, 5)
nums.append!(5)
nums.append!("str") # error, nums is Array<Int>

Declare an empty array:

let users = []Int # Array<Int>
users = [1, 2, 3] # OK
users = [4, 5, 6] # error
let users = []Int|String # Array<Int|String>
users = [30, "Bob"]

Array operations

let nums! = [1, 2, 3]
nums! << 4
println(nums) // "[1, 2, 3, 4]"

let names! = ["John"]
names! << "Peter"
names! << "Sam"
# names << 10  <-- This will not compile. `names` is an array of strings.
Console.puts(names.len) // "3"
Console.puts("Alex" in names) # "false"
names.each {
    Console.puts(e)
}

<< is an operator that appends a value to the end of the array. It can also append an entire array.

val in array returns true if the array contains val.

Array methods

Arrays can be efficiently filtered and mapped with the .filter() and .map() methods:

let nums = [1, 2, 3, 4, 5, 6]
let even = nums.filter{e % 2 == 0}
Console.puts(even) // [2, 4, 6]

let words = ["hello", "world"]
let upper = words.map{e.toUpper()}
Console.puts(upper) # ["HELLO", "WORLD"]

e is a builtin variable which refers to element currently being processed in filter/map methods.

Multidimensional Arrays

Arrays can have more than one dimension.

2d array example:

let a = [][]Int # Array<Array<Int>>
a = [[0,0,0],[1,1,1]]

Hash

let h = ["one":1, "two":2] # Hash<String, Int>("one":1, "two":2)
Console.puts(h["one"]) # 1
let m! = Hash<String,Int>  #
m["one"]! = 1 # m.insert("one", 1)
m["two"]! = 2
Console.puts(m["one"]) #
m.delete!("two")

imports

Selective imports

Module import aliasing

Statements & expressions

If

let a = 10
let b = 20
if (a < b) {
    println('$a < $b')
} elif (a > b) { 
    println('$a > $b')
}
else {
    println('$a == $b')
}

if can be used as an expression:

let num = 500
let s = if (num % 2 == 0) {
    "even"
else 
    "odd"
}
Console.puts(s) # "even"

In operator

in allows to check whether an array or a map contains an element.

let nums = [1, 2, 3]
println(1 in nums) # true

let m = ["one": 1, "two": 2]
println("one" in m) # true

For loop

tansang has only one looping keyword: for.

for(true) {
    do
}

when

let os = "windows"
Console.print("tansang is running on ")
when(os) {
    "mac": print("macOS"),
    "linux":{print("linux"), print("OS")},     
    else: print("OtherOS")
}

A when statement is a shorter way to write a sequence of if - else statements. finding matching branch, the following statement block will be run. The else branch will be run when no other branches match.

A when expression returns the final expression from each branch.
let number = 2
let s = when(number) {
    1:"one",
    2:"two", 
    else:"many"
}
Consloe.puts(s) # "two"

enum Color {
    red,
    blue,
    green,
}

fn is_red_or_blue(c Color) bool {
    return when c {
        .red, .blue :   true, # comma can be used to test multiple values
        .green : false 
    }
}

A when statement can also be used to branch on the variants of an enum by using the shorthand .variant_here syntax. An else branch is not allowed when all the branches are exhaustive.

let c = 'T'
let typ = when(c) {
    '0'..'9' :  "digit",
    'A'..'Z' : "uppercase",
    'a'..'z' : "lowercase",
    else      : "other"
}
println(typ) # 'lowercase'

You can also use ranges as match patterns. If the value falls within the range of a branch, that branch will be executed.

Generics

type Main

fn init() {
    Console.puts(sum(5 + 1))
    Console.puts(sum(3.14 + 3.2))
}

fn sum(a T1, b T1) T1 {
    return a + b
}