closures.md

Closures in TechScript

Closures are functions that capture variables from their enclosing lexical scope.

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🏗️ Capturing State

When you declare a function inside another function, the inner function has access to the outer function's parameters and local variables:

do create_counter(start_val)
    count = start_val
    
    # Return a closure
    send do()
        count += 1
        send count
    end
end

counter = create_counter(10)
say counter() # 11
say counter() # 12

In this example, the variable count is captured and bound to the returned anonymous function even after create_counter has finished executing.

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🧬 Capture by Reference

Captured variables are captured by reference, meaning modifications are visible across multiple invocations:

do build_multiplier(factor)
    send do(value) -> value * factor
end

triple = build_multiplier(3)
say triple(10) # 30