Trait FnPredicateOps 

pub trait FnPredicateOps<T>:
    Fn(&T) -> bool
    + Sized
    + 'static {
    // Provided methods
    fn and<P>(self, other: P) -> BoxPredicate<T>
       where P: Predicate<T> + 'static,
             T: 'static { ... }
    fn or<P>(self, other: P) -> BoxPredicate<T>
       where P: Predicate<T> + 'static,
             T: 'static { ... }
    fn not(self) -> BoxPredicate<T>
       where T: 'static { ... }
    fn nand<P>(self, other: P) -> BoxPredicate<T>
       where P: Predicate<T> + 'static,
             T: 'static { ... }
    fn xor<P>(self, other: P) -> BoxPredicate<T>
       where P: Predicate<T> + 'static,
             T: 'static { ... }
    fn nor<P>(self, other: P) -> BoxPredicate<T>
       where P: Predicate<T> + 'static,
             T: 'static { ... }
}

Extension trait providing logical composition methods for closures.

This trait is automatically implemented for all closures and function pointers that match Fn(&T) -> bool, enabling method chaining starting from a closure.

Examples

use prism3_function::predicate::{Predicate, FnPredicateOps};

let is_positive = |x: &i32| *x > 0;
let is_even = |x: &i32| x % 2 == 0;

// Combine predicates using extension methods
let pred = is_positive.and(is_even);
assert!(pred.test(&4));
assert!(!pred.test(&3));

Author

Haixing Hu

Provided Methods

fn and<P>(self, other: P) -> BoxPredicate<T>

where P: Predicate<T> + 'static, T: 'static,

Returns a predicate that represents the logical AND of this predicate and another.

Parameters

• other - The other predicate to combine with. Note: This parameter is passed by value and will transfer ownership. If you need to preserve the original predicate, clone it first (if it implements Clone). Can be:
  • Another closure
  • A function pointer
  • A BoxPredicate<T>, RcPredicate<T>, or ArcPredicate<T>

Returns

A BoxPredicate representing the logical AND.

Examples

use prism3_function::predicate::{Predicate, FnPredicateOps};

let is_positive = |x: &i32| *x > 0;
let is_even = |x: &i32| x % 2 == 0;

let combined = is_positive.and(is_even);
assert!(combined.test(&4));
assert!(!combined.test(&3));

Examples found in repository

examples/predicate_demo.rs (line 63)

fn basic_closure_predicates() {
    println!("--- 1. Basic Closure Predicate Usage ---");

    // Simple closure predicate
    let is_positive = |x: &i32| *x > 0;
    println!("Is 5 positive? {}", is_positive.test(&5));
    println!("Is -3 positive? {}", is_positive.test(&-3));

    // Combining closures
    let is_even = |x: &i32| x % 2 == 0;
    let is_positive_and_even = is_positive.and(is_even);
    println!("Is 4 positive and even? {}", is_positive_and_even.test(&4));
    println!("Is 5 positive and even? {}", is_positive_and_even.test(&5));

    // Using predicates with iterators
    let numbers = [-2, -1, 0, 1, 2, 3, 4, 5];
    let positives: Vec<_> = numbers
        .iter()
        .filter(|x| is_positive.test(x))
        .copied()
        .collect();
    println!("Positive numbers: {:?}", positives);
}

examples/mutator_once_conditional_demo.rs (lines 77-80)

fn main() {
    println!("=== MutatorOnce Conditional Execution Examples ===\n");

    // 1. Basic conditional execution - when condition is satisfied
    println!("1. Basic conditional execution - when condition is satisfied");
    let data = vec![1, 2, 3];
    let mutator = BoxMutatorOnce::new(move |x: &mut Vec<i32>| {
        println!("   Extending vector with data: {:?}", data);
        x.extend(data);
    });
    let conditional = mutator.when(|x: &Vec<i32>| {
        println!("   Checking condition: !x.is_empty()");
        !x.is_empty()
    });

    let mut target = vec![0];
    println!("   Initial: {:?}", target);
    conditional.mutate_once(&mut target);
    println!("   Result: {:?}\n", target);

    // 2. Conditional execution - when condition is not satisfied
    println!("2. Conditional execution - when condition is not satisfied");
    let data = vec![4, 5, 6];
    let mutator = BoxMutatorOnce::new(move |x: &mut Vec<i32>| {
        println!("   This should not be executed");
        x.extend(data);
    });
    let conditional = mutator.when(|x: &Vec<i32>| {
        println!("   Checking condition: x.len() > 10");
        x.len() > 10
    });

    let mut target = vec![0];
    println!("   Initial: {:?}", target);
    conditional.mutate_once(&mut target);
    println!("   Result: {:?} (unchanged)\n", target);

    // 3. Using BoxPredicate
    println!("3. Using BoxPredicate");
    let pred = BoxPredicate::new(|x: &Vec<i32>| {
        println!("   Predicate: checking if vector is not empty");
        !x.is_empty()
    });
    let data = vec![7, 8, 9];
    let mutator = BoxMutatorOnce::new(move |x: &mut Vec<i32>| {
        println!("   Adding data: {:?}", data);
        x.extend(data);
    });
    let conditional = mutator.when(pred);

    let mut target = vec![0];
    println!("   Initial: {:?}", target);
    conditional.mutate_once(&mut target);
    println!("   Result: {:?}\n", target);

    // 4. Using composed predicate
    println!("4. Using composed predicate");
    let pred = (|x: &Vec<i32>| {
        println!("   Condition 1: !x.is_empty()");
        !x.is_empty()
    })
    .and(|x: &Vec<i32>| {
        println!("   Condition 2: x.len() < 10");
        x.len() < 10
    });
    let data = vec![10, 11, 12];
    let mutator = BoxMutatorOnce::new(move |x: &mut Vec<i32>| {
        println!("   Adding data: {:?}", data);
        x.extend(data);
    });
    let conditional = mutator.when(pred);

    let mut target = vec![0];
    println!("   Initial: {:?}", target);
    conditional.mutate_once(&mut target);
    println!("   Result: {:?}\n", target);

    // 5. If-then-else with or_else - when branch
    println!("5. If-then-else with or_else - when branch");
    let data1 = vec![1, 2, 3];
    let data2 = vec![99];
    let mutator = BoxMutatorOnce::new(move |x: &mut Vec<i32>| {
        println!("   When branch: adding {:?}", data1);
        x.extend(data1);
    })
    .when(|x: &Vec<i32>| {
        println!("   Checking: !x.is_empty()");
        !x.is_empty()
    })
    .or_else(move |x: &mut Vec<i32>| {
        println!("   Else branch: adding {:?}", data2);
        x.extend(data2);
    });

    let mut target = vec![0];
    println!("   Initial: {:?}", target);
    mutator.mutate_once(&mut target);
    println!("   Result: {:?}\n", target);

    // 6. If-then-else with or_else - else branch
    println!("6. If-then-else with or_else - else branch");
    let data1 = vec![4, 5, 6];
    let data2 = vec![99];
    let mutator = BoxMutatorOnce::new(move |x: &mut Vec<i32>| {
        println!("   When branch: adding {:?}", data1);
        x.extend(data1);
    })
    .when(|x: &Vec<i32>| {
        println!("   Checking: x.is_empty()");
        x.is_empty()
    })
    .or_else(move |x: &mut Vec<i32>| {
        println!("   Else branch: adding {:?}", data2);
        x.extend(data2);
    });

    let mut target = vec![0];
    println!("   Initial: {:?}", target);
    mutator.mutate_once(&mut target);
    println!("   Result: {:?}\n", target);

    // 7. Conditional with integers
    println!("7. Conditional with integers");
    let mutator = BoxMutatorOnce::new(|x: &mut i32| {
        println!("   Multiplying by 2");
        *x *= 2;
    })
    .when(|x: &i32| {
        println!("   Checking: *x > 0");
        *x > 0
    });

    let mut positive = 5;
    println!("   Initial (positive): {}", positive);
    mutator.mutate_once(&mut positive);
    println!("   Result: {}\n", positive);

    // 8. Conditional with integers - not executed
    println!("8. Conditional with integers - not executed");
    let mutator = BoxMutatorOnce::new(|x: &mut i32| {
        println!("   This should not be executed");
        *x *= 2;
    })
    .when(|x: &i32| {
        println!("   Checking: *x > 0");
        *x > 0
    });

    let mut negative = -5;
    println!("   Initial (negative): {}", negative);
    mutator.mutate_once(&mut negative);
    println!("   Result: {} (unchanged)\n", negative);

    // 9. Chaining conditional mutators
    println!("9. Chaining conditional mutators");
    let data1 = vec![1, 2];
    let cond1 = BoxMutatorOnce::new(move |x: &mut Vec<i32>| {
        println!("   First mutator: adding {:?}", data1);
        x.extend(data1);
    })
    .when(|x: &Vec<i32>| {
        println!("   First condition: !x.is_empty()");
        !x.is_empty()
    });

    let data2 = vec![3, 4];
    let cond2 = BoxMutatorOnce::new(move |x: &mut Vec<i32>| {
        println!("   Second mutator: adding {:?}", data2);
        x.extend(data2);
    })
    .when(|x: &Vec<i32>| {
        println!("   Second condition: x.len() < 10");
        x.len() < 10
    });

    let chained = cond1.and_then(cond2);

    let mut target = vec![0];
    println!("   Initial: {:?}", target);
    chained.mutate_once(&mut target);
    println!("   Result: {:?}\n", target);

    // 10. Complex conditional chain
    println!("10. Complex conditional chain");
    let data1 = vec![1, 2];
    let data2 = vec![99];
    let data3 = vec![5, 6];

    let mutator = BoxMutatorOnce::new(move |x: &mut Vec<i32>| {
        println!("   When branch: adding {:?}", data1);
        x.extend(data1);
    })
    .when(|x: &Vec<i32>| {
        println!("   Checking: !x.is_empty()");
        !x.is_empty()
    })
    .or_else(move |x: &mut Vec<i32>| {
        println!("   Else branch: adding {:?}", data2);
        x.extend(data2);
    })
    .and_then(move |x: &mut Vec<i32>| {
        println!("   Final step: adding {:?}", data3);
        x.extend(data3);
    });

    let mut target = vec![0];
    println!("   Initial: {:?}", target);
    mutator.mutate_once(&mut target);
    println!("   Result: {:?}\n", target);

    // 11. Real-world scenario: data validation and processing
    println!("11. Real-world scenario: data validation and processing");

    struct DataProcessor {
        on_valid: Option<BoxMutatorOnce<Vec<String>>>,
        on_invalid: Option<BoxMutatorOnce<Vec<String>>>,
    }

    impl DataProcessor {
        fn new<V, I>(on_valid: V, on_invalid: I) -> Self
        where
            V: FnOnce(&mut Vec<String>) + 'static,
            I: FnOnce(&mut Vec<String>) + 'static,
        {
            Self {
                on_valid: Some(BoxMutatorOnce::new(on_valid)),
                on_invalid: Some(BoxMutatorOnce::new(on_invalid)),
            }
        }

        fn process(mut self, data: &mut Vec<String>) {
            let is_valid = !data.is_empty() && data.iter().all(|s| !s.is_empty());
            println!(
                "   Data validation: {}",
                if is_valid { "VALID" } else { "INVALID" }
            );

            if is_valid {
                if let Some(callback) = self.on_valid.take() {
                    callback.mutate_once(data);
                }
            } else if let Some(callback) = self.on_invalid.take() {
                callback.mutate_once(data);
            }
        }
    }

    let valid_suffix = vec!["processed".to_string()];
    let invalid_marker = vec!["[INVALID]".to_string()];

    let processor = DataProcessor::new(
        move |data| {
            println!("   Valid data callback: adding suffix");
            data.extend(valid_suffix);
        },
        move |data| {
            println!("   Invalid data callback: adding error marker");
            data.clear();
            data.extend(invalid_marker);
        },
    );

    let mut valid_data = vec!["item1".to_string(), "item2".to_string()];
    println!("   Processing valid data: {:?}", valid_data);
    processor.process(&mut valid_data);
    println!("   Result: {:?}\n", valid_data);

    println!("=== Examples completed ===");
}

fn or<P>(self, other: P) -> BoxPredicate<T>

where P: Predicate<T> + 'static, T: 'static,

Returns a predicate that represents the logical OR of this predicate and another.

Parameters

• other - The other predicate to combine with. Note: This parameter is passed by value and will transfer ownership. If you need to preserve the original predicate, clone it first (if it implements Clone). Can be:
  • Another closure
  • A function pointer
  • A BoxPredicate<T>, RcPredicate<T>, or ArcPredicate<T>
  • Any type implementing Predicate<T>

Returns

A BoxPredicate representing the logical OR.

Examples

use prism3_function::predicate::{Predicate, FnPredicateOps};

let is_negative = |x: &i32| *x < 0;
let is_large = |x: &i32| *x > 100;

let combined = is_negative.or(is_large);
assert!(combined.test(&-5));
assert!(combined.test(&150));
assert!(!combined.test(&50));

fn not(self) -> BoxPredicate<T>

where T: 'static,

Returns a predicate that represents the logical negation of this predicate.

Returns

A BoxPredicate representing the logical negation.

fn nand<P>(self, other: P) -> BoxPredicate<T>

where P: Predicate<T> + 'static, T: 'static,

Returns a predicate that represents the logical NAND (NOT AND) of this predicate and another.

NAND returns true unless both predicates are true. Equivalent to !(self AND other).

Parameters

• other - The other predicate to combine with. Note: This parameter is passed by value and will transfer ownership. If you need to preserve the original predicate, clone it first (if it implements Clone). Accepts closures, function pointers, or any Predicate<T> implementation.

Returns

A BoxPredicate representing the logical NAND.

Examples

use prism3_function::predicate::{Predicate, FnPredicateOps};

let is_positive = |x: &i32| *x > 0;
let is_even = |x: &i32| x % 2 == 0;

let nand = is_positive.nand(is_even);
assert!(nand.test(&3));   // !(true && false) = true
assert!(!nand.test(&4));  // !(true && true) = false

fn xor<P>(self, other: P) -> BoxPredicate<T>

where P: Predicate<T> + 'static, T: 'static,

Returns a predicate that represents the logical XOR (exclusive OR) of this predicate and another.

XOR returns true if exactly one of the predicates is true.

Parameters

• other - The other predicate to combine with. Note: This parameter is passed by value and will transfer ownership. If you need to preserve the original predicate, clone it first (if it implements Clone). Accepts closures, function pointers, or any Predicate<T> implementation.

Returns

A BoxPredicate representing the logical XOR.

Examples

use prism3_function::predicate::{Predicate, FnPredicateOps};

let is_positive = |x: &i32| *x > 0;
let is_even = |x: &i32| x % 2 == 0;

let xor = is_positive.xor(is_even);
assert!(xor.test(&3));    // true ^ false = true
assert!(!xor.test(&4));   // true ^ true = false
assert!(!xor.test(&-1));  // false ^ false = false

fn nor<P>(self, other: P) -> BoxPredicate<T>

where P: Predicate<T> + 'static, T: 'static,

Returns a predicate that represents the logical NOR (NOT OR) of this predicate and another.

NOR returns true only when both predicates are false. Equivalent to !(self OR other).

Parameters

• other - The other predicate to combine with. Note: This parameter is passed by value and will transfer ownership. If you need to preserve the original predicate, clone it first (if it implements Clone). Accepts closures, function pointers, or any Predicate<T> implementation.

Returns

A BoxPredicate representing the logical NOR.

Examples

use prism3_function::predicate::{Predicate, FnPredicateOps};

let is_positive = |x: &i32| *x > 0;
let is_even = |x: &i32| x % 2 == 0;

let nor = is_positive.nor(is_even);
assert!(nor.test(&-3));   // !(false || false) = true
assert!(!nor.test(&4));   // !(true || true) = false
assert!(!nor.test(&3));   // !(true || false) = false

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl<T, F> FnPredicateOps<T> for F

where F: Fn(&T) -> bool + 'static,