57 lines
1.4 KiB
JavaScript
57 lines
1.4 KiB
JavaScript
|
// chaining
|
||
|
|
|
||
|
|
// load math.js (using node.js)
|
||
|
|
const math = require('..')
|
||
|
|
|
||
|
|
// create a chained operation using the function `chain(value)`
|
||
|
|
// end a chain using done(). Let's calculate (3 + 4) * 2
|
||
|
|
const a = math.chain(3)
|
||
|
|
.add(4)
|
||
|
|
.multiply(2)
|
||
|
|
.done()
|
||
|
|
print(a) // 14
|
||
|
|
|
||
|
|
// Another example, calculate square(sin(pi / 4))
|
||
|
|
const b = math.chain(math.pi)
|
||
|
|
.divide(4)
|
||
|
|
.sin()
|
||
|
|
.square()
|
||
|
|
.done()
|
||
|
|
print(b) // 0.5
|
||
|
|
|
||
|
|
// A chain has a few special methods: done, toString, valueOf, get, and set.
|
||
|
|
// these are demonstrated in the following examples
|
||
|
|
|
||
|
|
// toString will return a string representation of the chain's value
|
||
|
|
const chain = math.chain(2).divide(3)
|
||
|
|
const str = chain.toString()
|
||
|
|
print(str) // "0.6666666666666666"
|
||
|
|
|
||
|
|
// a chain has a function .valueOf(), which returns the value hold by the chain.
|
||
|
|
// This allows using it in regular operations. The function valueOf() acts the
|
||
|
|
// same as function done().
|
||
|
|
print(chain.valueOf()) // 0.66666666666667
|
||
|
|
print(chain + 2) // 2.6666666666667
|
||
|
|
|
||
|
|
// the function subset can be used to get or replace sub matrices
|
||
|
|
const array = [[1, 2], [3, 4]]
|
||
|
|
const v = math.chain(array)
|
||
|
|
.subset(math.index(1, 0))
|
||
|
|
.done()
|
||
|
|
print(v) // 3
|
||
|
|
|
||
|
|
const m = math.chain(array)
|
||
|
|
.subset(math.index(0, 0), 8)
|
||
|
|
.multiply(3)
|
||
|
|
.done()
|
||
|
|
print(m) // [[24, 6], [9, 12]]
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Helper function to output a value in the console. Value will be formatted.
|
||
|
|
* @param {*} value
|
||
|
|
*/
|
||
|
|
function print (value) {
|
||
|
|
const precision = 14
|
||
|
|
console.log(math.format(value, precision))
|
||
|
|
}
|