The Shape of Functional Programming
@fogus
@fogus
var array = [0,1,2,3,4,5];
var transformed = [];
for (var i = 0; i < array.length; i++) {
transformed.push(array[i] + 100);
}
transformed;
var array = [0,1,2,3,4,5];
// Underscore
_.map(array, function(n) {
return n + 100;
});
// Lemonad
L.map(L.add(100), array);
var array = [0,1,2,3,4,5];
var keepers = [];
for (var i = 0; i < array.length; i++) {
if (array[i] % 2 === 0) {
keepers.push(array[i]);
}
}
keepers;
var array = [0,1,2,3,4,5];
// Underscore
_.filter(array, function(n) {
if (n % 2 === 0) {
return true;
}
else {
return false;
}
});
// Lemonad
L.filter(L.isEven, array);
var array = [0,1,2,3,4,5];
var sum = 0;
for (var i = 0; i < array.length; i++) {
sum += array[i];
}
sum;
var array = [0,1,2,3,4,5];
// Underscore
_.reduce(array, function(acc, n) {
return acc + n;
}, 0);
// Lemonad
L.reduce(L.uncurry(L.add), 0, array);
Fun.js at a glance
- Simple data
- Small functions
- Larger abstractions from simple data
- Larger abstractions from composing small functions
- OO to supplement
- No dogma
simple data
42
small functions
function nth(array, index) {
return array[index];
}
nth(['a', 'b', 'c'], 1);
abstractions, composed from primitives
var table = [
{id: '555-55-5555',
name: 'Moe',
age: 45},
{id: '777-77-7777',
name: 'Curly',
age: 47}
];
var table = [
{id: '555-55-5555',
name: 'Moe',
age: 45},
{id: '777-77-7777',
name: 'Curly',
age: 47}
];
function cell(table, col, row){
return table[row][col];
}
cell(table, "name", 0);
cell(table, "age", 0);
Codd.js
var itunes = [
{'artist' : 'Sun Ra',
'genre' : 'Jazz',
'plays' : 379},
{'artist' : 'Om',
'genre' : 'Doom',
'plays' : 22},
{'artist' : 'Can',
'genre' : 'Prog',
'plays' : 190},
{'artist' : 'Popol Vuh',
'genre' : 'Prog',
'plays' : 285}
];
var itunes = [
{'artist' : 'Sun Ra',
'genre' : 'Jazz',
'plays' : 379},
{'artist' : 'Om',
'genre' : 'Doom',
'plays' : 22},
{'artist' : 'Can',
'genre' : 'Prog',
'plays' : 190},
{'artist' : 'Popol Vuh',
'genre' : 'Prog',
'plays' : 285}
];
function cell(col, row, table) {
var entry = table[row];
return entry && entry[col];
}
cell('artist', 1, itunes);
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
function cell(col, row, table) {
var entry = table[row];
return entry && entry[col];
}
function getArtists(library) {
var ret = [];
for (var i = 0; i < library.length; i++) {
ret.push(cell('artist', i, library));
}
return ret;
}
getArtists(itunes);
Codd.project
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
Codd.project(itunes, ['artist']);
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
Codd.project(itunes, ['artist', 'plays']);
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
Codd.project(itunes, ['artist', 'plays']); /*** SELECT artist,plays FROM itunes; ***/
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
_.sortBy(Codd.project(itunes, ['artist', 'plays']), 'plays');
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
_.sortBy(Codd.project(itunes, ['artist', 'plays']), 'plays'); /*** SELECT artist,plays FROM itunes ORDER BY plays; ***/
Codd.rename
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
_.sortBy(Codd.rename(Codd.project(itunes, ['artist', 'plays']), {artist: 'band'}), 'plays');
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
_.sortBy(Codd.rename(Codd.project(itunes, ['artist', 'plays']), {artist: 'band'}), 'plays');
/***
SELECT artist AS "band", plays
FROM itunes
ORDER BY plays;
***/
Codd.restrict
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
_.sortBy(Codd.restrict(Codd.rename(Codd.project(itunes, ['artist', 'plays']), {artist: 'band'}), function(cell) { return cell.plays > 200 }), 'plays');
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
_.sortBy(Codd.restrict(Codd.rename(Codd.project(itunes, ['artist', 'plays']), {artist: 'band'}), function(cell) { return cell.plays > 200 }), 'plays');
/***
SELECT artist AS "band", plays
FROM itunes
WHERE plays > 200
ORDER BY plays;
***/
Abstractions from functions: composition and pipelines
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
_.size(Codd.col(itunes, 'artist'));
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
_.compose(_.size, Codd.col)(itunes, 'artist');
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
_.compose(_.size, Codd.col)(itunes, 'artist'); _.size( Codd.col( itunes, 'artist'));
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
L.pipeline(itunes, Codd.col('artist'), _.size);
var itunes = [{'artist' : 'Sun Ra', 'genre' : 'Jazz', 'plays' : 379}, {'artist' : 'Om', 'genre' : 'Doom', 'plays' : 22}, {'artist' : 'Can', 'genre' : 'Prog', 'plays' : 190}, {'artist' : 'Popol Vuh', 'genre' : 'Prog', 'plays' : 285}];
var orderBy = L.rcurry2(_.sortBy);
L.pipeline(itunes,
Codd.RQL.select(['artist', 'plays']),
Codd.RQL.as({artist: 'band'}),
Codd.RQL.where(Codd.RQL.field('plays', L.gt(200))),
orderBy('plays'));
/***
SELECT artist AS "band", plays
FROM itunes
WHERE plays > 200
ORDER BY plays;
***/
