reverse range

tonivade · Oct 13, 2024 · ec1153d · ec1153d
1 parent 6fe3827
commit ec1153d
Show file tree

Hide file tree

Showing 4 changed files with 62 additions and 5 deletions.
diff --git a/core/src/main/java/com/github/tonivade/purefun/core/Validator.java b/core/src/main/java/com/github/tonivade/purefun/core/Validator.java
@@ -337,6 +337,14 @@ static Validator<String, String> maxLength(int length, Producer<String> message)
     return lowerThan(length, message).compose(String::length);
   }
 
+  static <T extends Comparable<T>> Validator<String, T> nonEquals(T value) {
+    return nonEquals(value, () -> "require non equals to " + value);
+  }
+
+  static <T extends Comparable<T>> Validator<String, T> nonEquals(T value, Producer<String> message) {
+    return from(input -> input.compareTo(value) != 0, message);
+  }
+
   static Validator<String, Integer> positive() {
     return greaterThan(0);
   }

diff --git a/core/src/main/java/com/github/tonivade/purefun/data/Range.java b/core/src/main/java/com/github/tonivade/purefun/data/Range.java
@@ -10,29 +10,47 @@
 
 import com.github.tonivade.purefun.core.Function1;
 import com.github.tonivade.purefun.core.Tuple;
-
 import static com.github.tonivade.purefun.core.Function1.identity;
 import static com.github.tonivade.purefun.core.Precondition.check;
 import static com.github.tonivade.purefun.core.Precondition.greaterThanOrEquals;
 import static com.github.tonivade.purefun.type.Validation.mapN;
 import static com.github.tonivade.purefun.type.Validation.requireGreaterThanOrEqual;
 import static com.github.tonivade.purefun.type.Validation.requireLowerThan;
 import static com.github.tonivade.purefun.type.Validation.requireLowerThanOrEqual;
+import static com.github.tonivade.purefun.type.Validation.requireNonEquals;
+
+public record Range(int begin, int end, int increment) implements Iterable<Integer> {
 
-public record Range(int begin, int end) implements Iterable<Integer> {
+  public Range(int begin, int end) {
+    this(begin, end, 1);
+  }
 
   public Range {
-    check(greaterThanOrEquals(end, begin));
+    check(() -> increment != 0);
+    if (increment > 0) {
+      check(greaterThanOrEquals(end, begin));
+    } else {
+      check(greaterThanOrEquals(begin, end));
+    }
+  }
+
+  public Range reverse() {
+    return new Range(end, begin, -increment);
   }
 
   public boolean contains(int value) {
+    if (increment < 0) {
+      return mapN(
+          requireGreaterThanOrEqual(value, end),
+          requireLowerThan(value, begin), Tuple::of).isValid();
+    }
     return mapN(
         requireGreaterThanOrEqual(value, begin),
         requireLowerThan(value, end), Tuple::of).isValid();
   }
 
   public int size() {
-    return end - begin;
+    return Math.abs(end - begin);
   }
 
   public ImmutableArray<Integer> collect() {
@@ -44,6 +62,9 @@ public <T> ImmutableArray<T> map(Function1<? super Integer, ? extends T> map) {
   }
 
   public IntStream intStream() {
+    if (increment < 0) {
+      return IntStream.range(end, begin).map(i -> begin - i + end - 1);
+    }
     return IntStream.range(begin, end);
   }
 
@@ -58,12 +79,19 @@ public Iterator<Integer> iterator() {
 
   @Override
   public String toString() {
-    return String.format("Range(%d..%d)", begin, end);
+    return String.format("Range(%d..%d, increment=%d)", begin, end, increment);
   }
 
   public static Range of(int begin, int end) {
     return mapN(
         requireLowerThanOrEqual(begin, end),
         requireGreaterThanOrEqual(end, begin), Range::new).getOrElseThrow();
   }
+
+  public static Range of(int begin, int end, int increment) {
+    return mapN(
+        requireLowerThanOrEqual(begin, end),
+        requireGreaterThanOrEqual(end, begin),
+        requireNonEquals(increment, 0), Range::new).getOrElseThrow();
+  }
 }
diff --git a/core/src/main/java/com/github/tonivade/purefun/type/Validation.java b/core/src/main/java/com/github/tonivade/purefun/type/Validation.java
@@ -11,6 +11,7 @@
 import static com.github.tonivade.purefun.core.Validator.lowerThan;
 import static com.github.tonivade.purefun.core.Validator.lowerThanOrEqual;
 import static com.github.tonivade.purefun.core.Validator.nonEmpty;
+import static com.github.tonivade.purefun.core.Validator.nonEquals;
 import static com.github.tonivade.purefun.core.Validator.nonNullAnd;
 import static com.github.tonivade.purefun.core.Validator.positive;
 import static com.github.tonivade.purefun.data.Sequence.listOf;
@@ -247,6 +248,10 @@ static Validation<String, String> requireNonEmpty(String value) {
     return nonNullAnd(nonEmpty()).validate(value);
   }
 
+  static Validation<String, Integer> requireNonEquals(Integer value, int x) {
+    return nonNullAnd(nonEquals(x)).validate(value);
+  }
+
   static Validation<String, Integer> requirePositive(Integer value) {
     return nonNullAnd(positive()).validate(value);
   }

diff --git a/core/src/test/java/com/github/tonivade/purefun/data/RangeTest.java b/core/src/test/java/com/github/tonivade/purefun/data/RangeTest.java
@@ -29,6 +29,22 @@ public void range() {
     );
   }
 
+  @Test
+  public void revRange() {
+    Range range = Range.of(1, 10).reverse();
+
+    assertAll(
+        () -> assertEquals(0, Range.of(1, 1).reverse().size()),
+        () -> assertEquals(10, range.begin()),
+        () -> assertEquals(1, range.end()),
+        () -> assertEquals(9, range.size()),
+        () -> assertFalse(range.contains(0)),
+        () -> assertFalse(range.contains(10)),
+        () -> assertTrue(range.contains(1)),
+        () -> assertEquals(arrayOf(9, 8, 7, 6, 5, 4, 3, 2, 1), range.collect())
+    );
+  }
+
   @Test
   public void validRange() {
     assertThrows(IllegalArgumentException.class, () -> Range.of(10, 1));