expressions.md

Expressions

Lang expressions cover values, operators, calls, data access, and a small amount of syntax sugar over Python execution.

Syntax

• Comments use //.
• Numbers, strings, and booleans are expression values.
• Assignment uses =.
• Arithmetic and comparison operators follow standard programming notation such as +, *, and ==.
• Function calls use name(arg1, arg2).
• Member access uses object.member.
• Arrays use [a, b, c]; indexing uses value[index].
• Ranges use start..end and start..=end.
• Distribution uses args -> recipient.
• Lambdas use (args) => expr.
• Raw Python blocks use #[python] ... #[endpython].

Examples

Literals, comments, and assignment

// literal smoke test
flag = true
message = "ok"
if flag == true { print(message) } else { print("no") }

Calls and operators

fn add(a, b) { a + b }
value = add(1, 2)
if value == 3 { print(value) } else { print(0) }

Member access

counter.value
self.name = name

Arrays and indexing

values = [1, 2, 3]
print(values[1])

Ranges

for x in 1..3 {
    print(x)
}

Python note: ranges transpile to an iterator-backed Python range(...) wrapper.

Distribution

1..10 -> print

Python note: distribution forwards the left-hand value as arguments to the right-hand callable.

Lambdas

value = 2
print(((n) => n + 1)(value))

Raw Python interop

#[python]
class Counter:
    def __init__(self, value):
        self.value = value
#[endpython]

counter = Counter(5)
print(counter.value)

Python note: code inside a raw Python block is emitted directly into the generated Python module.

Notes

• The official docs cover only tested expression forms.
• Raw Python interop is part of the public surface, but its body is Python, not Lang.
• Arrays currently transpile through the runtime Iterator helper rather than a plain Python list object.