feat(iterables): Add non-by aggregation functions

Add non-by variants of sum, min, max and mean functions.

re: #6

Author: danielrbradley

src/iterables.ts

@@ -615,6 +615,18 @@ export function* reverse<T>(source: Iterable<T>): Iterable<T> {
   }
 }
 
+/**
+ * Returns the sum of the values in the collection.
+ * @param source The input collection.
+ */
+export function sum(source: Iterable<number>): number {
+  let sum = 0
+  for (const item of source) {
+    sum += item
+  }
+  return sum
+}
+
 /**
  * Returns the sum of the values returned by the selector for each element in the collection.
  * @param selector A function to transform each element into a summable value.
@@ -640,6 +652,24 @@ export function sumBy<T>(a: any, b?: any): any {
   return partial ? exec : exec(a)
 }
 
+/**
+ * Returns the maximum of the values in the collection.
+ * @param source The input collection.
+ * @throws If the collection is empty.
+ */
+export function max(source: Iterable<number>): number {
+  let max: number | null = null
+  for (const item of source) {
+    if (max === null || item > max) {
+      max = item
+    }
+  }
+  if (max === null) {
+    throw new Error(`Can't find max of an empty collection`)
+  }
+  return max
+}
+
 /**
  * Returns the maximum of the values returned by the selector for each element in the collection.
  * @param selector A function to transform each element into a comparable value.
@@ -673,6 +703,24 @@ export function maxBy<T>(a: any, b?: any): any {
   return partial ? exec : exec(a)
 }
 
+/**
+ * Returns the minimum of the values in the collection.
+ * @param source The input collection.
+ * @throws If the collection is empty.
+ */
+export function min(source: Iterable<number>): number {
+  let min: number | null = null
+  for (const item of source) {
+    if (min === null || item < min) {
+      min = item
+    }
+  }
+  if (min === null) {
+    throw new Error(`Can't find min of an empty collection`)
+  }
+  return min
+}
+
 /**
  * Returns the minimum of the values returned by the selector for each element in the collection.
  * @param selector A function to transform each element into a comparable value.
@@ -706,6 +754,24 @@ export function minBy<T>(a: any, b?: any): any {
   return partial ? exec : exec(a)
 }
 
+/**
+ * Returns the mean (average) of the values in the collection.
+ * @param source The input collection.
+ * @throws If the collection is empty.
+ */
+export function mean(source: Iterable<number>): number {
+  let sum = 0
+  let count = 0
+  for (const item of source) {
+    sum += item
+    count++
+  }
+  if (count === 0) {
+    throw new Error(`Can't find mean of an empty collection`)
+  }
+  return sum / count
+}
+
 /**
  * Returns the mean (average) of the values returned by the selector for each element in the collection.
  * @param selector A function to transform each element into a summable value.

test/iterable.test.ts

@@ -824,6 +824,20 @@ describe('reverse', () => {
   })
 })
 
+describe('sum', () => {
+  it('sums without partial application', () => {
+    expect(
+      Iterables.sum(
+        (function*() {
+          yield 21
+          yield 2
+          yield 18
+        })()
+      )
+    ).toEqual(41)
+  })
+})
+
 describe('sumBy', () => {
   it('sums ages', () => {
     expect(
@@ -850,6 +864,23 @@ describe('sumBy', () => {
   })
 })
 
+describe('max', () => {
+  it('finds max', () => {
+    expect(
+      Iterables.max(
+        (function*() {
+          yield 2
+          yield 21
+          yield 18
+        })()
+      )
+    ).toEqual(21)
+  })
+  it('fails on empty collection', () => {
+    expect(() => Iterables.max([])).toThrow(`Can't find max of an empty collection`)
+  })
+})
+
 describe('maxBy', () => {
   it('finds max age', () => {
     expect(
@@ -881,6 +912,23 @@ describe('maxBy', () => {
   })
 })
 
+describe('min', () => {
+  it('finds min', () => {
+    expect(
+      Iterables.min(
+        (function*() {
+          yield 21
+          yield 2
+          yield 18
+        })()
+      )
+    ).toEqual(2)
+  })
+  it('fails on empty collection', () => {
+    expect(() => Iterables.min([])).toThrow(`Can't find min of an empty collection`)
+  })
+})
+
 describe('minBy', () => {
   it('finds min age', () => {
     expect(
@@ -912,6 +960,24 @@ describe('minBy', () => {
   })
 })
 
+describe('mean', () => {
+  it('finds mean', () => {
+    expect(
+      Iterables.mean(
+        (function*() {
+          yield 21
+          yield 2
+          yield 18
+          yield 39
+        })()
+      )
+    ).toEqual(20)
+  })
+  it('fails on empty collection', () => {
+    expect(() => Iterables.mean([])).toThrow(`Can't find mean of an empty collection`)
+  })
+})
+
 describe('meanBy', () => {
   it('finds mean age', () => {
     expect(