mostly-adequate-guid
Currying
Can't Live If Livin' Is without You
The concept is simple: You can call a function with fewer arguments than it expects. It returns a function that takes the remaining arguments.
const add = x => y => x + y;
const increment = add(1);
const addTen = add(10);
increment(2); // 3
addTen(2); // 12match(/r/g, 'hello world'); // [ 'r' ]
const hasLetterR = match(/r/g); // x => x.match(/r/g)
hasLetterR('hello world'); // [ 'r' ]
hasLetterR('just j and s and t etc'); // null
filter(hasLetterR, ['rock and roll', 'smooth jazz']); // ['rock and roll']
const removeStringsWithoutRs = filter(hasLetterR); // xs => xs.filter(x => x.match(/r/g))
removeStringsWithoutRs(['rock and roll', 'smooth jazz',
'drum circle']); // ['rock and roll', 'drum circle']
const noVowels = replace(/[aeiou]/ig); // (r,x) => x.replace(/[aeiou]/ig, r)
const censored = noVowels('*'); // x => x.replace(/[aeiou]/ig, '*')
censored('Chocolate Rain'); // 'Ch*c*l*t* R**n'Giving a function fewer arguments than it expects is typically called partial application. Partially applying a function can remove a lot of boiler plate code.
Currying does exactly this: each single argument returns a new function expecting the remaining arguments. Currying is handy and I very much enjoy working with curried functions on a daily basis. It is a tool for the belt that makes functional programming less verbose and tedious.
Coding by Composing
Functional Husbandry
const compose = (...fns) => (...args) =>
fns.reduceRight((res, fn) => [fn.call(null, ...res)], args)[0];Don't be scared! This is the level-9000-super-Saiyan-form of compose. For the sake of reasoning, let's drop the variadic implementation and consider a simpler form that can compose two functions together. Once you get your head around that, you can push the abstraction further and consider it simply works for any number of functions (we could even prove that)! Here's a more friendly compose for you my dear readers:
const compose2 = (f, g) => x => f(g(x));Composition feels like function husbandry. You, breeder of functions, select two with traits you'd like to combine and mash them together to spawn a brand new one. Usage is as follows:
const toUpperCase = x => x.toUpperCase();
const exclaim = x => `${x}!`;
const shout = compose(exclaim, toUpperCase);
shout('send in the clowns'); // "SEND IN THE CLOWNS!"Title Text
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Title Text
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mostly-adequate-guid(part 2)
By sddtc
mostly-adequate-guid(part 2)
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