ramda-decimal

Ramda wrapper to Decimal.js

Use Decimal.js arbitrary precision maths in Ramda style. Immutable. Composable. Curry-able.

Drop-in replacements for most Ramda math functions.

const R = require('ramda);
const RD = require('ramda-decimal);

const annualTax = R.pipe(
    R.pluck(income),
    RD.sum,
    RD.times(TAX_RATE),
);

const format = RD.fixed(2);

console.log(format(annualTax(months)));

Liberal inputs, conservative outputs

Like Decimal.js, RD accepts Decimals, number primitives and strings that look like numbers. RD does this by calling new Decimal() on any input.

All RD functions return Decimals.

Constants

ZERO and ONE are defined as constants. Use them! They're immutable.

Parameter order

When there is a corresponding Ramda function, RD uses the same parameter order. This does mean that curried relation functions are unintuitive (in my opinion) in the same way as Ramda:

const f = RD.gt(5);
return f(6); // false: gt(5,6)

Where there is no corresponding Ramda function, we have flipped the parameters when it seems useful for point-free coding:

const formatToPennies = RD.toFixed(2);

Currying and efficiency

For brevity the documentation suggests that (for example) RD.add(a)(b) is equivalent to new Decimal(a).plus(b). The reality is a bit better than that. RD.add(a) stores any Decimal it creates for reuse. Hence in:

const addTen = RD.add(10);
const n110 = addTen(100);
const n210 = addTen(200);

... new Decimal(10) is only run once.

Mixed style

Returned values are just Decimal objects, so you are free to combine styles if you want to:

const displayTotal = RD.sum(vals).fixed(2, Decimal.ROUND_HALF_UP);

Docs

Modules

Typedefs

ramda-decimal

Ramda-style curried functions wrapping the methods of Decimal.js

DecimalLike : Decimal | number | string

A Decimal, number, or a string containing a number. That is, any valid parameter to new Decimal(...)

Kind: global typedef

.abs(n) ⇒ Decimal

Equivalent to new Decimal(n).absoluteValue()

Kind: static function

| Param | Type | | --- | --- | | n | DecimalLike |

.add(a, b) ⇒ Decimal

Equivalent to new Decimal(a).plus(b)

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike | | b | DecimalLike |

.ceil(n) ⇒ Decimal

Equivalent to new Decimal(n).ceil()

Kind: static function

| Param | Type | | --- | --- | | n | DecimalLike |

.eq(a, b) ⇒ boolean

Equivalent to new Decimal(a).equals(b)

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike | | b | DecimalLike |

.divide(a, b) ⇒ Decimal

Equivalent to new Decimal(a).dividedBy(b)

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike | | b | DecimalLike |

.divideBy(a, b) ⇒ Decimal

Equivalent to new Decimal(b).dividedBy(a)

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike | | b | DecimalLike |

.floor(n) ⇒ Decimal

Equivalent to new Decimal(n).floor()

Kind: static function

| Param | Type | | --- | --- | | n | DecimalLike |

.gt(a, b) ⇒ boolean

Equivalent to new Decimal(a).gt(b)

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike | | b | DecimalLike |

.gte(a, b) ⇒ boolean

Equivalent to new Decimal(a).gte(b)

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike | | b | DecimalLike |

.lt(a, b) ⇒ boolean

Equivalent to new Decimal(a).lt(b)

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike | | b | DecimalLike |

.lte(a, b) ⇒ boolean

Equivalent to new Decimal(a).lte(b)

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike | | b | DecimalLike |

.multiply(a, b) ⇒ Decimal

Equivalent to new Decimal(a).times(b)

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike | | b | DecimalLike |

.negate(a) ⇒ Decimal

Equivalent to new Decimal(a).negated()

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike |

.round(a) ⇒ Decimal

Equivalent to new Decimal(a).round()

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike |

.subtract(a, b) ⇒ Decimal

Equivalent to new Decimal(a).minus(b)

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike | | b | DecimalLike |

.toFixed(roundingMode, num) ⇒ Decimal

Equivalent to new Decimal(num).toFixed(roundingMode)

See Decimal.js docs for ROUNDING_MODE constants

Kind: static function

| Param | Type | | --- | --- | | roundingMode | num | | num | DecimalLike |

.toNumber(a) ⇒ Number

Equivalent to new Decimal(a).toNumber()

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike |

.modulo(modulus, value) ⇒ Decimal

Equivalent to new Decimal(value).modulo(modulus)

Kind: static function

| Param | Type | | --- | --- | | modulus | DecimalLike | | value | DecimalLike |

.toPower(power, value) ⇒ Decimal

Equivalent to new Decimal(value).toPower(modulus)

Kind: static function

| Param | Type | | --- | --- | | power | DecimalLike | | value | DecimalLike |

.isPositive(a) ⇒ boolean

Equivalent to new Decimal(a).isPositive()

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike |

.isNegative(a) ⇒ boolean

Equivalent to new Decimal(a).isNegative()

Kind: static function

| Param | Type | | --- | --- | | a | DecimalLike |

.dec(a) ⇒ Decimal

Decrements a Decimal or value that may be converted into Decimal

Kind: static function
Returns: Decimal - a minus 1

| Param | Type | | --- | --- | | a | DecimalLike |

.inc(a) ⇒ Decimal

Increments a Decimal or value that may be converted into Decimal

Kind: static function
Returns: Decimal - a plus 1

| Param | Type | | --- | --- | | a | DecimalLike |

.sum(a) ⇒ Decimal

Returns the sum of an array of Decimals or values that may be converted into Decimal

Kind: static function
Returns: Decimal - The sum of the values in a

| Param | Type | | --- | --- | | a | Array.<DecimalLike> |

.product(a) ⇒ Decimal

Returns the product of an array of Decimals or values that may be converted into Decimal

Kind: static function
Returns: Decimal - The product of the values in a

| Param | Type | | --- | --- | | a | Array.<DecimalLike> |

.max(a, b) ⇒ Decimal

Returns the highest of a or b

Kind: static function
Returns: Decimal - The highest of a or b

| Param | Type | | --- | --- | | a | Array.<DecimalLike> | | b | Array.<DecimalLike> |

.min(a, b) ⇒ Decimal

Returns the lowest of a or b

Kind: static function
Returns: Decimal - The lowest of a or b

| Param | Type | | --- | --- | | a | Array.<DecimalLike> | | b | Array.<DecimalLike> |

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