Hanling

About

Hanling is a minimalist programming language designed for teaching. It features clean syntax, built-in contracts (require / ensure), and language-level unit tests (test blocks). The interpreter is a single Go binary — no dependencies, no setup.

Examples

Hello, World!

print("Hello, World!")

Variables & Arithmetic

x = 10
y = 3
print(x + y)   # 13
print(x / y)   # 3.3333...

Conditionals & Loops

if score >= 90 then
    print("A")
elseif score >= 80 then
    print("B")
else
    print("C")
end

for i in range(5) do
    print(i)
end

Functions with Contracts

function factorial(n)
    require n >= 0
    if n <= 1 then
        return 1
    end
    return n * factorial(n - 1)
ensure result > 0
end

print(factorial(5))   # 120

Lists & Maps

nums = [1, 2, 3]
append(nums, 4)
print(nums)   # [1, 2, 3, 4]

person = {"name": "Alice", "age": 30}
print(person["name"])   # Alice

Closures

function make_adder(x)
    function adder(n)
        return x + n
    end
    return adder
end

add5 = make_adder(5)
print(add5(3))   # 8

Error Handling

try
    num = int("abc")
catch e
    print("Failed: " + e)
end

Built-in Unit Tests

function add(a, b)
    return a + b
end

test "addition works"
    assert(add(2, 3) == 5)
    assert(add(-1, 1) == 0)
end

Features