numbers

Safely parse numbers from strings

Functions

parseIntM

Attempts to parse an integer from a string, using Maybe<number> to wrap the success or failure of the parse.

import { parseIntM } from '@execonline-inc/numbers';

parseIntM('123').getOrElseValue(0) // returns `123`
parseIntM('123.42').getOrElseValue(0) // returns `123`
parseIntM('Hello World!').getOrElseValue(0) // returns `0`

parseIntR

Attempts to parse an integer from a string, using Result<NumberParseFailure, number> to wrap the success or failure of the parse.

import { parseIntR } from '@execonline-inc/numbers';

parseIntR('123').getOrElseValue(0) // returns `123`
parseIntR('123.42').getOrElseValue(0) // returns `123`

parseIntR('Hello World').elseDo(console.warn).getOrElseValue(0)
// Prints object: { kind: 'number-parse-failure', message: `Couldn't parse string into a number` }
// Returns 0

parseIntT

Attempts to parse an integer from a string, using Task<NumberParseFailure, number> to wrap the success or failure of the parse.

import { parseIntT } from '@execonline-inc/numbers';

parseIntT('123').fork(() => {}, console.log); // Prints the integer 123
parseIntT('123.42').fork(() => {}, console.log); // Prints the integer 123

parseIntT('Hello World').fork(console.warn, () => {});
// Prints object: { kind: 'number-parse-failure', message: `Couldn't parse string into a number` }

percentage

Display a number as a percentage.

import { percentage } from '@execonline-inc/numbers';

percentage(42.22) // returns the string "42%"

Numeric Predicates

Compare numbers in a declarative way.

Functions

positive

Check if a value is greater than zero.

import { positive } from '@execonline-inc/numbers';

positive(10) // true
positive(0) // false

whenPositive

A function that returns Maybe is available

import { whenPositive } from '@execonline-inc/numbers';
import { nothing, just } from 'maybeasy';

const widgetMessage = (value: Maybe<number>) =>
  value
    .andThen(whenPositive)
    .map((count) => `${count} widgets still remain!`)
    .getOrElseValue("No remaining widgets!");

widgetMessage(just(7)) // "7 widgets still remain!"
widgetMessage(just(0)) // "No remaining widgets!"
widgetMessage(nothing()) // No remaining widgets!

gt

Check if a value is greater than.

import { gt } from '@execonline-inc/numbers';
import { just, isJust } from 'maybeasy';

const checkForGreaterThan = (value: number): boolean => just(value).map(gt(10)).isJust();

checkForGreaterThan(7) // evaluates to false
checkForGreaterThan(11) // evaluates to true

whenGt

A function that returns Maybe is available

import { gt, multiplyBy } from '@execonline-inc/numbers';

const checkForGreaterThanAndMultiply = (value: Maybe<number>) =>
  value
    .andThen(whenGt(7))
    .map(multiplyBy(6))
    .getOrElseValue(0);

checkForGreaterThanAndMultiply(4) // evaluates to 0
checkForGreaterThanAndMultiply(11) // evaluates to 66

Other Functions

The following functions work similarly. Many are available with versions that return Maybe.

lt

Less than

gte

Greater than or equal to

lte

Less than or equal to

eq

Equal to

neq

Not equal to

between

Takes a min and max as arguments, returns a boolean.

betweenEq

Takes a min and max as arguments, returns a boolean.

even

Value is even

odd

Value is odd

positive

Value is positive

negative

Value is negative

zero

Value is zero

multiplyBy

Multiplies the value by inputted value

divideBy

Divides the value by inputted value

add

Adds the value to inputted value

subtractBy

Subtracts the value from inputted value