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Functions

Functions

Basic Function Declaration

Functions are declared with the func keyword, followed by the name, parameters in parentheses, return type after ->, and a : to open the body:

functions.tg
func add(a: i32, b: i32) -> i32:
    return a + b


func greet(name: String) -> String:
    return "Hello " + name


func main() -> i32:
    let result = add(10, 32)
    print(result)       # Output: 42


    let msg = greet("Thagore")
    print(msg)          # Output: Hello Thagore
    return 0

Function Syntax

func <name>(<param1>: <type1>, <param2>: <type2>, ...) -> <return_type>:
    <body>

Rules

  1. Parameters must have explicit type annotations: name: Type
  2. Return type is specified after -> and before :
  3. return statement is required to return a value
  4. Indentation defines the function body

Entry Point: main

func main() -> i32 is the standard entry point for Thagore programs:

entry_point.tg
func main() -> i32:
    print("Program started")
    return 0    # 0 = success

Multiple Functions

Functions can call each other:

multi_func.tg
func square(n: i32) -> i32:
    return n * n


func sum_of_squares(a: i32, b: i32) -> i32:
    return square(a) + square(b)


func main() -> i32:
    let result = sum_of_squares(3, 4)
    print(result)    # Output: 25
    return 0

Recursive Functions

Thagore supports recursion natively:

fib.tg
func fib(n: i32) -> i32:
    if (n < 2):
        return n
    return fib(n - 1) + fib(n - 2)


func main() -> i32:
    let result = fib(35)
    print(result)    # Output: 9227465
    return 0

Functions with String Parameters

string_funcs.tg
func make_greeting(first: String, last: String) -> String:
    return "Hello, " + first + " " + last + "!"


func main() -> i32:
    let greeting = make_greeting("John", "Doe")
    print(greeting)
    return 0

Functions with Float Parameters

float_func.tg
func calc_circle(radius: f32) -> f32:
    let pi = 3.14159
    return 2.0 * pi * radius


func main() -> i32:
    let circumference = calc_circle(5.0)
    print(circumference)
    return 0

Functions with Default Parameters

Some standard library functions support default parameters:

default_params.tg
# In the standard library (lib/io.tg):
# func input_prompt(prompt: String = "") -> String:
#     ...


import io


func main() -> i32:
    let name = io.input_prompt("Enter your name: ")
    print("Hello, " + name)
    return 0

extern func — Foreign Function Declarations

Use extern func to declare external C functions (see FFI & Import for details):

extern_func.tg
extern func sqrtf(x: f32) -> f32
extern func pow(base: f64, exp: f64) -> f64


func main() -> i32:
    let h = sqrtf(9.0 + 16.0)
    print(h)    # Output: 5.0
    return 0