fn_transformer_ops_demo/
fn_transformer_ops_demo.rs

1/*******************************************************************************
2 *
3 *    Copyright (c) 2025.
4 *    3-Prism Co. Ltd.
5 *
6 *    All rights reserved.
7 *
8 ******************************************************************************/
9//! Demonstrates the usage of FnTransformerOps extension trait
10//!
11//! This example shows how to directly use and_then, compose, and when methods on closures,
12//! without explicitly wrapping them in BoxTransformer, RcTransformer, or ArcTransformer.
13
14use prism3_function::{FnTransformerOps, Transformer};
15
16fn main() {
17    println!("=== FnTransformerOps Example ===\n");
18
19    // 1. Basic and_then composition
20    println!("1. Basic and_then composition:");
21    let double = |x: i32| x * 2;
22    let to_string = |x: i32| x.to_string();
23    let composed = double.and_then(to_string);
24    println!(
25        "   double.and_then(to_string).apply(21) = {}",
26        composed.apply(21)
27    );
28    println!();
29
30    // 2. Chained and_then composition
31    println!("2. Chained and_then composition:");
32    let add_one = |x: i32| x + 1;
33    let double = |x: i32| x * 2;
34    let to_string = |x: i32| x.to_string();
35    let chained = add_one.and_then(double).and_then(to_string);
36    println!(
37        "   add_one.and_then(double).and_then(to_string).apply(5) = {}",
38        chained.apply(5)
39    ); // (5 + 1) * 2 = 12
40    println!();
41
42    // 3. compose reverse composition
43    println!("3. compose reverse composition:");
44    let double = |x: i32| x * 2;
45    let add_one = |x: i32| x + 1;
46    let composed = double.compose(add_one);
47    println!(
48        "   double.compose(add_one).apply(5) = {}",
49        composed.apply(5)
50    ); // (5 + 1) * 2 = 12
51    println!();
52
53    // 4. Conditional transformation when
54    println!("4. Conditional transformation when:");
55    let double = |x: i32| x * 2;
56    let conditional = double.when(|x: &i32| *x > 0).or_else(|x: i32| -x);
57    println!("   double.when(x > 0).or_else(negate):");
58    println!("     transform(5) = {}", conditional.apply(5)); // 10
59    println!("     transform(-5) = {}", conditional.apply(-5)); // 5
60    println!();
61
62    // 5. Complex composition
63    println!("5. Complex composition:");
64    let add_one = |x: i32| x + 1;
65    let double = |x: i32| x * 2;
66    let triple = |x: i32| x * 3;
67    let to_string = |x: i32| x.to_string();
68
69    let complex = add_one
70        .and_then(double.when(|x: &i32| *x > 5).or_else(triple))
71        .and_then(to_string);
72
73    println!("   add_one.and_then(double.when(x > 5).or_else(triple)).and_then(to_string):");
74    println!("     transform(1) = {}", complex.apply(1)); // (1 + 1) = 2 <= 5, so 2 * 3 = 6
75    println!("     transform(5) = {}", complex.apply(5)); // (5 + 1) = 6 > 5, so 6 * 2 = 12
76    println!("     transform(10) = {}", complex.apply(10)); // (10 + 1) = 11 > 5, so 11 * 2 = 22
77    println!();
78
79    // 6. Type conversion
80    println!("6. Type conversion:");
81    let to_string = |x: i32| x.to_string();
82    let get_length = |s: String| s.len();
83    let length_transformer = to_string.and_then(get_length);
84    println!(
85        "   to_string.and_then(get_length).apply(12345) = {}",
86        length_transformer.apply(12345)
87    ); // 5
88    println!();
89
90    // 7. Closures that capture environment
91    println!("7. Closures that capture environment:");
92    let multiplier = 3;
93    let multiply = move |x: i32| x * multiplier;
94    let add_ten = |x: i32| x + 10;
95    let with_capture = multiply.and_then(add_ten);
96    println!(
97        "   multiply(3).and_then(add_ten).apply(5) = {}",
98        with_capture.apply(5)
99    ); // 5 * 3 + 10 = 25
100    println!();
101
102    // 8. Function pointers
103    println!("8. Function pointers:");
104    fn double_fn(x: i32) -> i32 {
105        x * 2
106    }
107    fn add_one_fn(x: i32) -> i32 {
108        x + 1
109    }
110    let fn_composed = double_fn.and_then(add_one_fn);
111    println!(
112        "   double_fn.and_then(add_one_fn).apply(5) = {}",
113        fn_composed.apply(5)
114    ); // 5 * 2 + 1 = 11
115    println!();
116
117    // 9. Multi-conditional transformation
118    println!("9. Multi-conditional transformation:");
119    let abs = |x: i32| x.abs();
120    let double = |x: i32| x * 2;
121    let transformer = abs.when(|x: &i32| *x < 0).or_else(double);
122    println!("   abs.when(x < 0).or_else(double):");
123    println!("     transform(-5) = {}", transformer.apply(-5)); // abs(-5) = 5
124    println!("     transform(5) = {}", transformer.apply(5)); // 5 * 2 = 10
125    println!("     transform(0) = {}", transformer.apply(0)); // 0 * 2 = 0
126    println!();
127
128    println!("=== Example completed ===");
129}
fn_transformer_ops_demo/fn_transformer_ops_demo.rs

fn_transformer_ops_demo/
fn_transformer_ops_demo.rs
