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A powerful Swift framework for evaluating mathematical expressions
.package(url: "https://github.com/soulverteam/SoulverCore.git", from: "1.3.1")

What is SoulverCore?

SoulverCore is a math engine that calculates day-to-day mathematical expressions.

The design goals of SoulverCore are:

  • Sensible defaults appropriate for most use-cases (simple things are easy!)
  • A high level of customisability (complex things are possible!)
  • Excellent performance

Can I rely on SoulverCore for my project?

SoulverCore is the math engine from the popular notepad calculator app Soulver. Soulver has been available on Apple's platforms since 2005.

Soulver uses exactly the same version of SoulverCore that is available here. Everything you can do in Soulver, you can do using SoulverCore.

SoulverCore has been designed to have no 3rd party dependencies. It is written in 100% Swift. As such it works wherever Swift is available (including on Windows & Linux).

Apps using SoulverCore

  • Lacona - a powerful natural language assistant/launcher for macOS
  • Toolbox Pro - calculate with Soulver as part of your Siri Shortcuts on iOS


  • Xcode 12+
  • Swift 5.4+
  • SoulverCore is distributed as a binary framework (.xcframework) and includes builds for macOS (universal), iOS/iPadOS, and Mac Catalyst.

Installation using the Swift Package Manager (SPM)

Xcode 12 and later lets you integrate SoulverCore into your project using the Swift Package Manager.

In Xcode, go File > Swift Packages > Add Package Dependency and paste in the URL of this repository (https://github.com/soulverteam/SoulverCore).

Manual Installation

Drag SoulverCore.xcframework into the Frameworks, Libraries, and Embedded Content section of the General settings for your Mac or iOS target.

Getting Started

To calculate the result of a single expression, use a Calculator object:

import SoulverCore

let calculator = Calculator(customization: .standard)
let result = calculator.evaluate("123 + 456")
print("The answer is \(result.stringValue)") // prints 579

SoulverCore can perform all sorts of calculations, including unit conversions, date & calendar math, rate calculations, percentage phrase functions, time zone conversions, and much more. It also cleverly ignores "meaningless" words:

calculator.evaluate("$10 for lunch + 15% tip") // $11.50
calculator.evaluate("65 kg in pounds") // 154.32 lb
calculator.evaluate("40 as % of 90") // 25%
calculator.evaluate("$150 is 25% on what") // $120
calculator.evaluate("$25/hour * 14 hours of work") // $350.00
calculator.evaluate("January 30 2020 + 3 months 2 weeks 5 days") // 19 May
calculator.evaluate("9:35am in New York to Japan") // 10:35 pm
calculator.evaluate("$25k over 10 years at 7.5%") // $51,525.79 (compound interest)


Use a VariableList to set values for words or phrases in your expression:

let variableList = VariableList(variables:
        Variable(name: "a", value: "123"),
        Variable(name: "b", value: "456"),
calculator.evaluate("a + b", with: variableList) // 579        

Custom Units

You can add custom units to an EngineCustomization object required by the intializer on Calculator or LineCollection.

/// A good omakase EngineCustomization (the same used by Soulver.app)
var customization: EngineCustomization = .standard

/// Set an array of custom units defined in terms of an existing unit in SoulverCore
customization.customUnits = [
    CustomUnit(name: "parrots", definition: 15, equivalentUnit: .centimeters),
    CustomUnit(name: "python", definition: 570, equivalentUnit: .centimeters)

/// Create a Calculator using this customization
let calculator = Calculator(customization: customization)

/// python and parrots are now recognized as units
calculator.calculate("1 python in parrots") // 38 parrots

Multi-line Calculations

Use a LineCollection to represent a collection of lines to be evaluated. Like Calculator, you can customize the way a LineCollection interprets expressions with an EngineCustomization.

let multiLineText =
a = 10
b = 20
c = a + b
let lineCollection = LineCollection(multiLineText:
    multiLineText, customization: .standard)

/// Calculate the result of each line (synchronously)

/// Use subscripts to get access to particular lines' results
let result = lineCollection[2].result // 30

Currency Rates

The .standard EngineCustomization includes rates for 170 real-world currencies (that were accurate at the time the framework was last compiled).

You can (and should) update these currencies to the latest rates by setting valid API key credentials for CurrencyLayer (for fiat currencies) and Nomics (for crypto currencies) on the shared CurrencyList.

Alternatively use the .popular currency set to pull 33 common fiat currency rates from the European Central Bank, no API key required.

To fetch the latest rates, use SoulverCore's shared CurrencyList:

/// 33 popular currencies from the ECB, updated every weekday.

CurrencyList.shared.defaultCurrencySet = .popular 

CurrencyList.shared.refreshRates { (success) in
	if success {  
		/// The standard customization will now have the latest currency rates applied		
		let calculator = Calculator(customization: .standard)
		let result = calculator.calculate("10 USD in EUR")  		

Locale Settings

SoulverCore respects the decimal separator and thousands separator of the system locale. Alternatively, you can convert the standard EngineCustomization to another locale:

let europeanLocale = Locale(identifier: "en_DE")
let localizedCustomization = EngineCustomization.standard.convertTo(locale: europeanLocale)

let calculator = Calculator(customization: localizedCustomization)

 /// In Germany a comma is used as a decimal separator
calculator.calculate("1,2 + 3,4") // 4,6

Output Formatting

Use a FormattingPreferences to customize the way your result is formatted (how many decimal places to include, should the thousands separator be inserted, etc).

var formattingPreferences = FormattingPreferences()
formattingPreferences.dp = 2 // decimal places
calculator.formattingPreferences = formattingPreferences

calculator.calculate("π") // 3.14

Performance & Reliability

SoulverCore is fast. You can disable certain features for even greater performance (see EngineCustomization.featureFlags), but with the complete feature set most expressions are processed in 1-5 ms on an Intel Mac, and <1ms on an Apple Silicon Mac.

This performance is due to months of work optimizing every part of the calculation engine. Like the original Safari team, performance is measured after every change and commits with performance regressions are not accepted.

SoulverCore has an excellent test suite with more than 1,500 tests. Most bugs are fixed the same week they are reported.


In addition to English, SoulverCore is fully localized into German 🇩🇪, Russian 🇷🇺, and simplified Chinese 🇨🇳. Support for the romance languages (French, Spanish, etc) is planned for 2021.

See Also

Adding calculation capabilities to an NSTextView or UITextView

See the SoulverTextKit project for an example of how to integrate the SoulverCore math engine into a standard macOS or iOS text view.


You may use SoulverCore in personal or private projects. Please email us if you wish to use SoulverCore in a publicly available, or commercial project. We have various options available depending on your needs, including a free (with attribution) license.


Stars: 343
Last commit: 3 weeks ago

Release Notes

4 weeks ago
  • Added the ability to specify custom currency units in units other than USD
  • Minor bug fixes and performance increases

Swiftpack is being maintained by Petr Pavlik | @ptrpavlik | @swiftpackco