https://exercism.org/tracks/rust/exercises/isogram

rust/isogram/Cargo.toml

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+[package]
+edition = "2021"
+name = "isogram"
+version = "1.3.0"

rust/isogram/src/lib.rs

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+use std::collections::HashSet;
+
+
+pub fn check(candidate: &str) -> bool {
+    let lowercase_str = candidate.chars().filter(|c| c.is_alphabetic()).into_iter().collect::<String>().to_lowercase();
+    let s: HashSet<char> = HashSet::from_iter(lowercase_str.chars());
+    lowercase_str.len() == s.len()
+}

rust/isogram/tests/isogram.rs

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+use isogram::check;
+
+#[test]
+fn empty_string() {
+    assert!(check(""), "An empty string should be an isogram.")
+}
+
+#[test]
+fn only_lower_case_characters() {
+    assert!(check("isogram"), "\"isogram\" should be an isogram.")
+}
+
+#[test]
+fn one_duplicated_character() {
+    assert!(
+        !check("eleven"),
+        "\"eleven\" has more than one \'e\', therefore it is no isogram."
+    )
+}
+
+#[test]
+fn longest_reported_english_isogram() {
+    assert!(
+        check("subdermatoglyphic"),
+        "\"subdermatoglyphic\" should be an isogram."
+    )
+}
+
+#[test]
+fn one_duplicated_character_mixed_case() {
+    assert!(
+        !check("Alphabet"),
+        "\"Alphabet\" has more than one \'a\', therefore it is no isogram."
+    )
+}
+
+#[test]
+fn hypothetical_isogramic_word_with_hyphen() {
+    assert!(
+        check("thumbscrew-japingly"),
+        "\"thumbscrew-japingly\" should be an isogram."
+    )
+}
+
+#[test]
+fn isogram_with_duplicated_hyphen() {
+    assert!(
+        check("six-year-old"),
+        "\"six-year-old\" should be an isogram."
+    )
+}
+
+#[test]
+fn made_up_name_that_is_an_isogram() {
+    assert!(
+        check("Emily Jung Schwartzkopf"),
+        "\"Emily Jung Schwartzkopf\" should be an isogram."
+    )
+}
+
+#[test]
+fn duplicated_character_in_the_middle() {
+    assert!(
+        !check("accentor"),
+        "\"accentor\" has more than one \'c\', therefore it is no isogram."
+    )
+}