When Static Typing Is Helpful?

Allen Madsen

Customers don't care about static typing

Developers don't care about static typing

Static typing is just a tool

Customers care about

  • Stability - Will the stuff I use continue working?
  • Iteration Speed - When will you build the thing I want to use?
  • Task Speed - How long does it take me to complete a task? (e.g. Do pages take a long time to load?)

Developers care about

  • Cycle time - How quickly do I discover a mistake?
  • Iteration Speed - Does it feel like I'm just dragging on this feature?
  • Correctness - Will my code work?

Tools have trade-offs

Pros

Static typing as tests

class WrappedThing
  def run
    CalledThing.call
  end
end

class CalledThing
  def call
    :return_value
  end
end

allow_any_instance_of(CalledThing).to receive(:call).and_return(:return_value)
WrappingThing.run()
class WrappedThing
  def run
    CalledThing.cal
  end
end

Static typing as docs

def contact(customer: User): Unit = {
  send_email(customer.email)
}

# vs

def contact(customer) = {
  send_email(customer.email)
}

Static typing as performance enhancer

Static typing can lead to compile time performance optimizations. Though, this largely doesn't apply to languages that compile to javascript.

Cons

Types as noise

User user = new User;

Types as complexity

let foo = Option<Rc<Vec<u32>>>

Types as a constraint

All Programs

Correct programs

Typed programs

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