”Life is too short for imperative programming” John Hughes

Software Crisis, 1968—today Software project outcomes

In Large Companies

Technology adoption life cycle

The Erlang Story 1986—Erlang emerges at Ericsson –Functional language –Extra support for concurrency & fault tolerance Early 1990s—small products 1996 –Open Telecoms Platform (higher-order functions for robust telecom systems) –AXD 301 project starts

The AXD 301 ATM switch (telephone backbone) Born out of a failed project! 1,5 MLOC Erlang Seven nines reliability 4-10x better productivity, quality

Erlang Story II 1998—Erlang banned for new projects 1998—Open source Erlang 1998—Bluetail –Jane Walerud VD –Mail robustifier, Web prioritizer

SSL Accelerator Alteon WebSystems' SSL Accelerator offers phenomenal performance, management and scalability. –Network Computing

Kreditor Order 100:- Order details 97:- invoice 100:-

Founded May 2006 Selling… QuickCheck! –Extra feature: simplifies failing tests

Session Border Gateway: A Firewall for IP telephony Media Proxy Opens media pin- holes for calls in progress 2x10G Ethernet Hardware for packet forwarding Media Gateway Controller Monitors signalling traffic; opens and closes pinholes 2x1G Ethernet Linux ”blade” processor

Session Border Gateway: A Firewall for IP telephony Media Proxy Media Gateway Controller ITU standard protocol H.248 (Megaco) 150KLOC Erlang InterWork Description defines a subset

Session Border Gateway: A Firewall for IP telephony Media Proxy QuickCheck

Megaco Commands Context

Megaco Commands Context Termination Add

Megaco Commands Context Termination Add

Megaco Commands Context Termination Stream Modify

Megaco Commands Context Termination Stream Subtract

Megaco Commands Context Termination Stream Subtract

Megaco Commands Context

Command Sequences Normal sequence: Add Modify Add Modify Subtract We wanted to test other sequences that, according to the IWD, should work.

Add/Modify Error Modify assumes there are already two terminations in the context Same bug found in virtually every run! New ”bug precondition” needed for Modify Add Modify

Add/Subtract Error There one day, gone the next… This bug had just been found and fixed by the development team Add Subtract

Add/Add/Modify Error If the terminations have different numbers of streams Same underlying problem: Modify assumes each stream has two ends… Add Modify Add

Add/Add/Sub/Add… Error Extracted from a test case 160 commands long Caused by corrupt data- structures after the first Subtract Add Subtract Add Subtract

Derivatives trading in New York 10 Microsoft shares Option to buy ● for $100 anytime In 2007 Option to sell ● for $10 in Nov 2006

How do they do it? C++ plugins

Simon Peyton-Jones: Financial Contracts in Haskell anytime :: Contract -> Contract -- Acquire the underlying contract at -- any time before it expires (but -- you must acquire it)  The option to acquire 10 Microsoft shares, for $100, anytime between t1 and t2 years from now golden_handcuff = anytime shares shares = zero `or` (scaleK -100 (one Dollar) `and` scaleK 10 (one MSShare)) anytime : Choose when MS shares are a “currency” or : Choose whether

New Approach C++ plugins Haskell contract models

Functional programming on Wall Street –Proprietary trading –60 people –OCaml primary development language

The Cat Among the Pigeons

Two cores, each hyperthreaded