change: Restore lipsum_from_seed & lipsum_words_from_seed (#98)

I introduced the default feature `std` which enables the `rand`
package features `std` & `std_rng` for the `thread_rng()` function.
This allows user to use the rand package without adding it with the
right features to own `Cargo.toml`.

Cargo.toml

@@ -25,3 +25,7 @@ rand_chacha = "0.3.1"
 [dev-dependencies]
 version-sync = "0.9.4"
 rand = "0.8.5"
+
+[features]
+default = ["std"]
+std_rng = ["rand/std", "rand/std_rng"]

src/lib.rs

@@ -458,6 +458,30 @@ pub fn lipsum_with_rng(rng: impl Rng, n: usize) -> String {
     LOREM_IPSUM_CHAIN.with(|chain| chain.generate_with_rng_from(rng, n, ("Lorem", "ipsum")))
 }
 
+/// Generate `n` words of lorem ipsum text. The output will always start with
+/// "Lorem ipsum". The seed makes the sequence deterministic.
+///
+/// Deterministic sequences are useful for unit tests where you need random but
+/// consistent inputs or when users expect an infinitely extendable blind text
+/// string that does not change.
+///
+/// # Examples
+///
+/// ```
+/// use lipsum::lipsum_from_seed;
+///
+/// assert_eq!(lipsum_from_seed(23, 16),
+///     "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim.");
+/// ```
+///
+/// [`LOREM_IPSUM`]: constant.LOREM_IPSUM.html
+/// [`lipsum`]: fn.lipsum.html
+pub fn lipsum_from_seed(n: usize, seed: u64) -> String {
+    let rng = ChaCha20Rng::seed_from_u64(seed);
+    LOREM_IPSUM_CHAIN.with(|chain| chain.generate_with_rng_from(rng, n, ("Lorem", "ipsum")))
+}
+
+
 /// Generate `n` words of lorem ipsum text.
 ///
 /// The text is deterministically sampled from a Markov chain based on
@@ -499,6 +523,30 @@ pub fn lipsum_words_with_rng(rng: impl Rng, n: usize) -> String {
     LOREM_IPSUM_CHAIN.with(|chain| chain.generate_with_rng(rng, n))
 }
 
+/// Generate `n` random words of lorem ipsum text. The seed makes the sequence
+/// deterministic.
+///
+/// Deterministic sequences are useful for unit tests where you need random but
+/// consistent inputs or when users expect an infinitely extendable blind text
+/// string that does not change.
+///
+/// # Examples
+///
+/// ```
+/// use lipsum::lipsum_words_from_seed;
+///
+/// assert_eq!(lipsum_words_from_seed(7, 1234),
+///            "Anteponant iis, quae recordamur. Stulti autem malorum.");
+/// ```
+///
+/// [`LOREM_IPSUM`]: constant.LOREM_IPSUM.html
+/// [`lipsum_words`]: fn.lipsum_words.html
+pub fn lipsum_words_from_seed(n: usize, seed: u64) -> String {
+    let rng = ChaCha20Rng::seed_from_u64(seed);
+    LOREM_IPSUM_CHAIN.with(|chain| chain.generate_with_rng(rng, n))
+}
+
+
 /// Minimum number of words to include in a title.
 const TITLE_MIN_WORDS: usize = 3;
 /// Maximum number of words to include in a title.
@@ -681,4 +729,18 @@ mod tests {
             "A b bar a b a b bar a b x y b y x."
         );
     }
+
+    #[test]
+    fn seed_works() {
+        assert_eq!(
+            lipsum_words_from_seed(10, 100_000),
+            lipsum_words_from_seed(10, 100_000)
+        );
+        assert_eq!(lipsum_from_seed(30, 100_000), lipsum_from_seed(30, 100_000));
+        assert_ne!(
+            lipsum_words_from_seed(10, 100_000),
+            lipsum_words_from_seed(10, 100_001)
+        );
+        assert_ne!(lipsum_from_seed(30, 100_000), lipsum_from_seed(30, 100_001));
+    }
 }