Question 1

How do I add a custom function to Expression?

Accepted Answer

Define a symbol using .function with arity, and provide a closure in the symbols dictionary. For example, to add a 'square' function, use .function("square", arity: 1): { args in args[0] * args[0] } as shown in the README's symbols section.

Question 2

Is Expression faster than using JavaScriptCore for simple math?

Accepted Answer

Yes, the Benchmark example app demonstrates Expression consistently outperforms JavaScriptCore in both parsing and evaluation times, making it a superior choice for performance-critical Swift applications.

Question 3

Can Expression handle string concatenation and array literals?

Accepted Answer

With AnyExpression, yes. It supports string literals with single or double quotes, concatenation via +, and array literals like [1, 2, 3] with subscripting, similar to Swift syntax.

Question 4

How to make Expression evaluations thread-safe?

Accepted Answer

The evaluate() method is inherently thread-safe, so you can call it concurrently from multiple threads without additional synchronization, as noted in the Integration section.

Question 5

What's the difference between Expression and AnyExpression?

Accepted Answer

Expression works only with Double values for high-performance math, while AnyExpression handles any Swift type but with some performance overhead. Use Expression for numeric-heavy tasks and AnyExpression for mixed data like strings or dictionaries.

Question 6

How to disable caching in Expression to save memory?

Accepted Answer

Call Expression.flushCache() to clear all, or use Expression.parse() with usingCache: false to avoid caching specific expressions, as detailed in the Caching section for fine-grained control.

Expression

What is Expression?

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