|
| 1 | +fn main() { |
| 2 | + expr_zero_or_more("()"); |
| 3 | +} |
| 4 | + |
| 5 | +fn expr_zero_or_more(s: &str) -> Option<&str> { |
| 6 | + println!("expr_zero_or_more s={}", s); |
| 7 | + |
| 8 | + if s.len() == 0 { |
| 9 | + return Some(s); |
| 10 | + } |
| 11 | + |
| 12 | + let mut t = s; |
| 13 | + while t.len() > 0 { |
| 14 | + match expr_parens(t) { |
| 15 | + Some(u) => t = u, |
| 16 | + None => return None, |
| 17 | + } |
| 18 | + println!("expr_zero_or_more while t={}", t); |
| 19 | + } |
| 20 | + Some("") |
| 21 | +} |
| 22 | + |
| 23 | +fn expr_one_or_more(s: &str) -> Option<&str> { |
| 24 | + println!("expr_one_or_more s={}", s); |
| 25 | + |
| 26 | + let mut t = s; |
| 27 | + while t.len() > 0 { |
| 28 | + println!("expr_one_or_more while t={}", t); |
| 29 | + match expr_parens(t) { |
| 30 | + Some(u) => t = u, |
| 31 | + None => return Some(t), |
| 32 | + } |
| 33 | + println!("expr_one_or_more while match t={}", t); |
| 34 | + } |
| 35 | + Some("") |
| 36 | +} |
| 37 | + |
| 38 | +fn expr_parens(s: &str) -> Option<&str> { |
| 39 | + println!("expr_parens s={}", s); |
| 40 | + assert!(s.len() > 0); |
| 41 | + |
| 42 | + let next = &s[0..1]; |
| 43 | + match next { |
| 44 | + "(" => { |
| 45 | + println!("expr_parens s={} match ( &s[1..]={}", s, &s[1..]); |
| 46 | + |
| 47 | + if s.len() == 1 { |
| 48 | + return None |
| 49 | + } |
| 50 | + |
| 51 | + let peek = &s[1..2]; |
| 52 | + match peek { |
| 53 | + ")" => { |
| 54 | + println!("expr_parens s={} match ( peek ) &s[2..]={}", s, &s[1..]); |
| 55 | + Some(&s[2..]) |
| 56 | + }, |
| 57 | + _ => { |
| 58 | + |
| 59 | + let e = expr_one_or_more(&s[1..]); |
| 60 | + println!("expr_parens s={} match ( e={:?}", s, e); |
| 61 | + match e { |
| 62 | + Some(f) => { |
| 63 | + if f.len() >= 1 && &f[0..1] == ")" { |
| 64 | + println!("expr_parens s={} ( e={:?} return Some(&f[1..])={}", s, e, &f[1..]); |
| 65 | + Some(&f[1..]) |
| 66 | + } else { |
| 67 | + None |
| 68 | + } |
| 69 | + }, |
| 70 | + None => Some(s) |
| 71 | + } |
| 72 | + |
| 73 | + } |
| 74 | + } |
| 75 | + }, |
| 76 | + _ => None |
| 77 | + } |
| 78 | +} |
| 79 | + |
| 80 | +#[cfg(test)] |
| 81 | +mod tests { |
| 82 | + use super::*; |
| 83 | + |
| 84 | + #[test] |
| 85 | + #[should_panic(expected = "assertion failed: s.len() > 0")] |
| 86 | + fn test_expr_parens_empty_is_none() { |
| 87 | + let input = ""; |
| 88 | + let result = expr_parens(input); |
| 89 | + assert!(result.is_none()); |
| 90 | + } |
| 91 | + |
| 92 | + #[test] |
| 93 | + fn test_expr_parens_pair_is_some() { |
| 94 | + let input = "()"; |
| 95 | + let result = expr_parens(input); |
| 96 | + assert!(result.is_some()); |
| 97 | + } |
| 98 | + |
| 99 | + #[test] |
| 100 | + fn test_expr_parens_nested_is_some() { |
| 101 | + let input = "(())"; |
| 102 | + let result = expr_parens(input); |
| 103 | + assert!(result.is_some()); |
| 104 | + } |
| 105 | + |
| 106 | + #[test] |
| 107 | + fn test_expr_parens_nesteded_is_some() { |
| 108 | + let input = "((()))"; |
| 109 | + let result = expr_parens(input); |
| 110 | + assert!(result.is_some()); |
| 111 | + } |
| 112 | + |
| 113 | + #[test] |
| 114 | + fn test_expr_parens_single_is_none() { |
| 115 | + let input = "("; |
| 116 | + let result = expr_parens(input); |
| 117 | + assert!(result.is_none()); |
| 118 | + } |
| 119 | + |
| 120 | + #[test] |
| 121 | + fn test_empty_is_some() { |
| 122 | + let input = ""; |
| 123 | + let result = expr_zero_or_more(input); |
| 124 | + assert!(result.is_some()); |
| 125 | + } |
| 126 | + |
| 127 | + #[test] |
| 128 | + fn test_single_is_none() { |
| 129 | + let input = "("; |
| 130 | + let result = expr_zero_or_more(input); |
| 131 | + assert!(result.is_none()); |
| 132 | + } |
| 133 | + |
| 134 | + #[test] |
| 135 | + fn test_parens_is_some() { |
| 136 | + let input = "()"; |
| 137 | + let result = expr_zero_or_more(input); |
| 138 | + assert!(result.is_some()); |
| 139 | + } |
| 140 | + |
| 141 | + #[test] |
| 142 | + fn test_parens_pairs_is_some() { |
| 143 | + let input = "()()"; |
| 144 | + let result = expr_zero_or_more(input); |
| 145 | + assert!(result.is_some()); |
| 146 | + } |
| 147 | + |
| 148 | + #[test] |
| 149 | + fn test_expr_zero_or_more_3_parens_pairs_is_some() { |
| 150 | + let input = "()()()"; |
| 151 | + let result = expr_zero_or_more(input); |
| 152 | + assert!(result.is_some()); |
| 153 | + } |
| 154 | + |
| 155 | + #[test] |
| 156 | + fn test_parens_nested_is_some() { |
| 157 | + let input = "(())"; |
| 158 | + let result = expr_zero_or_more(input); |
| 159 | + assert!(result.is_some()); |
| 160 | + } |
| 161 | + |
| 162 | + #[test] |
| 163 | + fn test_parens_nesteded_is_some() { |
| 164 | + let input = "((()))"; |
| 165 | + let result = expr_zero_or_more(input); |
| 166 | + assert!(result.is_some()); |
| 167 | + } |
| 168 | + |
| 169 | + #[test] |
| 170 | + fn test_parens_extra_open_is_none() { |
| 171 | + let input = "()("; |
| 172 | + let result = expr_zero_or_more(input); |
| 173 | + assert!(result.is_none()); |
| 174 | + } |
| 175 | + |
| 176 | + #[test] |
| 177 | + fn test_parens_pair_extra_open_is_none() { |
| 178 | + let input = "()()("; |
| 179 | + let result = expr_zero_or_more(input); |
| 180 | + assert!(result.is_none()); |
| 181 | + } |
| 182 | + |
| 183 | + #[test] |
| 184 | + fn test_parens_nested_pair_extra_open_is_none() { |
| 185 | + let input = "(())(()())("; |
| 186 | + let result = expr_zero_or_more(input); |
| 187 | + assert!(result.is_none()); |
| 188 | + } |
| 189 | + |
| 190 | + #[test] |
| 191 | + fn test_parens_complex_is_some() { |
| 192 | + let input = "(())(()())()"; |
| 193 | + let result = expr_zero_or_more(input); |
| 194 | + assert!(result.is_some()); |
| 195 | + } |
| 196 | + |
| 197 | + #[test] |
| 198 | + fn test_parens_extra_closed_is_none() { |
| 199 | + let input = "())"; |
| 200 | + let result = expr_zero_or_more(input); |
| 201 | + assert!(result.is_none()); |
| 202 | + } |
| 203 | +} |
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