PrediKit allows you to write NSPredicates and NSExpressions using native Swift code. Just write an expression like:

NSPredicate.withClosure { obj in
    obj["numberOfDesiredItems"] < countElements(obj["items"])
}

And you'll get an equivalent predicate without having to fumble around with the NSPredicate format syntax.

PrediKit overloads many Swift features with variants that return equivalent NSExpressions:

• Arithmetic operators (+, -, *, /, and %)
• Bitwise operators (\<\<, \>\>, &, |, ^, and ~)
• pow(x, y), sqrt(x), log10(x), log(x), exp(x), floor(x), ciel(x), abs(x), and trunc(x)
• countElements(list), minElement(list), and maxElement(list)
• uppercaseString and lowercaseString properties on NSExpression
• distanceFromLocation(loc) method on NSExpression
• arc4random() and arc4random_uniform(x), giving a different number each time the expression is evaluated
• New dynamicDate class property on NSDate, giving the date at the time the expression is evaluated

It also overloads a number of boolean operations to return NSPredicates:

• Basic comparisons (==, !=, <, <=, >, and >=), plus any() and all() functions to expose NSPredicate's ability to search inside a collection
• Basic logic operations (&&, ||, and !)
• contains(haystack, needle)
• Limited support for testing ranges (including ranges of NSExpressions constructed with ..< or ...) with ~=

Finally, it includes the Unicode set operators ∪ (union), ∩ (intersect), and ∖ (minus).

Currently these operators are available everywhere in your code. I would like to use a wrapper struct to avoid mistaken uses, but the Swift compiler choked when I tried this.

Any other bugs should be reported on GitHub. Pull requests are welcome.

Brent Royal-Gordon, Architechies brent@architechies.com

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