ExpressionParser

A little package that provides a simple arithmetic expression hierarchy.

It can store arbitrarily nested expressions using numbers of Double precision, the binary operators +, -, *, and /, the unary operators + and -, and parentheses for grouping.

The expression structure can be parsed directly from a String or it can be de- and encoded via Codable.

Installation

Add this line to the dependencies of your Swift Package:

.package(url: "https://github.com/Zollerboy1/ExpressionParser.git", from: "1.0.0")

and add the module ExpressionParser to your target's dependencies.

Usage

You can just create an expression hierarchy from a string:

import ExpressionParser

let expressionString = "5+6*(2+3)"

let expression = try ParsedExpression(from: expressionString)

print(expression) // prints "5.0 + 6.0 * (2.0 + 3.0)"

print(expression.value) // prints "35.0"

You can also decode an expression using Codable, e.g. from JSON:

import ExpressionParser
import Foundation

let jsonString = """
[
    5,
    "2.5e-1 + 4",
    "1 / 3"
]
"""

let jsonData = jsonString.data(using: .utf8)!

let decoder = JSONDecoder()

let array = try! decoder.decode([ParsedExpression].self, from: jsonData)

print(array) // prints "[5.0, 0.25 + 4.0, 1.0 / 3.0]"

print(array.map(\.value)) // prints "[5.0, 4.25, 0.3333333333333333]"

As you can see, ParsedExpression will try to decode numbers as well as strings from JSON (or every other format you have a Decoder for).