This photo of the Louis Vieux Elm Tree was taken by Willard Balderson, Wamego, in 1986. The tree stood 90 feet high with a crown spread of 104 feet, and a trunk circumference of 317 inches. For several years the Louis Vieux Elm Tree held the title of U.S. Champion. The estimated age of the elm tree was 300 years and since 1986 succumbed to age, weather, and disease leaving only a stump. In 2011, even the stump, which the Pottawatomie County Historical Society attempted to save, protect and shelter, was burned down, leaving nothing but a pile of ashes.

为什么 Elm 类似语言很稀罕？未来怎样？

如何评价Elm 编程语言？

Mailboxes

So in both cases we are writing contracts that say “I require input with this shape, and I will give you output with that shape.” This is the essence of ruling out runtime errors in Elm. We always know what kind of values a function needs and what kind it produces, so we can just check that we always follow these rules.