diff --git a/complex128/README.md b/complex128/README.md
index ec5a5f51..107be45e 100644
--- a/complex128/README.md
+++ b/complex128/README.md
@@ -1620,6 +1620,60 @@ var count = context.count;
// returns 3
```
+
+
+#### Complex128Array.prototype.reduce( reducerFn\[, initialValue] )
+
+Applies a provided callback function to each element of the array, in order, passing in the return value from the calculation on the preceding element and returning the accumulated result upon completion.
+
+```javascript
+var real = require( '@stdlib/complex/real' );
+var imag = require( '@stdlib/complex/imag' );
+var cadd = require( '@stdlib/math/base/ops/cadd' );
+
+var arr = new Complex128Array( 3 );
+
+arr.set( [ 1.0, 1.0 ], 0 );
+arr.set( [ 2.0, 2.0 ], 1 );
+arr.set( [ 3.0, 3.0 ], 2 );
+
+var z = arr.reduce( cadd );
+// returns
+
+var re = real( z );
+// returns 6.0
+
+var im = imag( z );
+// returns 6.0
+```
+
+The reducer function is provided four arguments:
+
+- **acc**: accumulated result.
+- **value**: current array element.
+- **index**: current array element index.
+- **arr**: the array on which this method was called.
+
+By default, the function initializes the accumulated result to the first element in the array and passes the second array element as `value` during the first invocation of the provided callback. To begin accumulation from a different starting value and pass in the first array element as `value` during the first invocation of the provided callback, provide an `initialValue` argument.
+
+```javascript
+var real = require( '@stdlib/complex/real' );
+
+function reducer( acc, v ) {
+ acc += real( v );
+ return acc;
+}
+
+var arr = new Complex128Array( 3 );
+
+arr.set( [ 1.0, 1.0 ], 0 );
+arr.set( [ 2.0, 2.0 ], 1 );
+arr.set( [ 3.0, 3.0 ], 2 );
+
+var z = arr.reduce( reducer, 0.0 );
+// returns 6.0
+```
+
#### Complex128Array.prototype.reverse()
diff --git a/complex128/benchmark/benchmark.reduce.js b/complex128/benchmark/benchmark.reduce.js
new file mode 100644
index 00000000..b6a3c8a4
--- /dev/null
+++ b/complex128/benchmark/benchmark.reduce.js
@@ -0,0 +1,52 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2023 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var bench = require( '@stdlib/bench' );
+var cadd = require( '@stdlib/math/base/ops/cadd' );
+var isComplexLike = require('@stdlib/assert/is-complex-like' );
+var pkg = require( './../package.json' ).name;
+var Complex128Array = require( './../lib' );
+
+
+// MAIN //
+
+bench( pkg+':reduce', function benchmark( b ) {
+ var out;
+ var arr;
+ var i;
+
+ arr = new Complex128Array( [ 1, 2, 3, 4, 5, 6 ] );
+
+ b.tic();
+ for ( i = 0; i < b.iterations; i++ ) {
+ out = arr.reduce( cadd );
+ if ( typeof out !== 'object' ) {
+ b.fail( 'should return an object' );
+ }
+ }
+ b.toc();
+ if ( !isComplexLike( out ) ) {
+ b.fail( 'should return a complex number' );
+ }
+ b.pass( 'benchmark finished' );
+ b.end();
+});
diff --git a/complex128/benchmark/benchmark.reduce.length.js b/complex128/benchmark/benchmark.reduce.length.js
new file mode 100644
index 00000000..538b8a1e
--- /dev/null
+++ b/complex128/benchmark/benchmark.reduce.length.js
@@ -0,0 +1,104 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2023 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var bench = require( '@stdlib/bench' );
+var pow = require( '@stdlib/math/base/special/pow' );
+var cadd = require( '@stdlib/math/base/ops/cadd' );
+var isComplexLike = require('@stdlib/assert/is-complex-like' );
+var Complex128 = require( '@stdlib/complex/float64' );
+var pkg = require( './../package.json' ).name;
+var Complex128Array = require( './../lib' );
+
+
+// FUNCTIONS //
+
+/**
+* Creates a benchmark function.
+*
+* @private
+* @param {PositiveInteger} len - array length
+* @returns {Function} benchmark function
+*/
+function createBenchmark( len ) {
+ var arr;
+ var i;
+
+ arr = [];
+ for ( i = 0; i < len; i++ ) {
+ arr.push( new Complex128( i, i ) );
+ }
+ arr = new Complex128Array( arr );
+
+ return benchmark;
+
+ /**
+ * Benchmark function.
+ *
+ * @private
+ * @param {Benchmark} b - benchmark instance
+ */
+ function benchmark( b ) {
+ var out;
+ var i;
+
+ b.tic();
+ for ( i = 0; i < b.iterations; i++ ) {
+ out = arr.reduce( cadd );
+ if ( typeof out !== 'object' ) {
+ b.fail( 'should return an object' );
+ }
+ }
+ b.toc();
+ if ( !isComplexLike( out ) ) {
+ b.fail( 'should return a complex number' );
+ }
+ b.pass( 'benchmark finished' );
+ b.end();
+ }
+}
+
+
+// MAIN //
+
+/**
+* Main execution sequence.
+*
+* @private
+*/
+function main() {
+ var len;
+ var min;
+ var max;
+ var f;
+ var i;
+
+ min = 1; // 10^min
+ max = 6; // 10^max
+
+ for ( i = min; i <= max; i++ ) {
+ len = pow( 10, i );
+ f = createBenchmark( len );
+ bench( pkg+':reduce:len='+len, f );
+ }
+}
+
+main();
diff --git a/complex128/docs/types/index.d.ts b/complex128/docs/types/index.d.ts
index 55491c41..2b5b7728 100644
--- a/complex128/docs/types/index.d.ts
+++ b/complex128/docs/types/index.d.ts
@@ -195,6 +195,60 @@ type TernaryMapFcn = ( this: U, value: Complex128, index: number, arr: Comple
*/
type MapFcn = NullaryMapFcn | UnaryMapFcn | BinaryMapFcn | TernaryMapFcn;
+/**
+* Reducer function invoked for each element in an array.
+*
+* @returns accumulated result
+*/
+type NullaryReducer = () => U;
+
+/**
+* Reducer function invoked for each element in an array.
+*
+* @param acc - accumulated result
+* @returns accumulated result
+*/
+type UnaryReducer = ( acc: U ) => U;
+
+/**
+* Reducer function invoked for each element in an array.
+*
+* @param acc - accumulated result
+* @param value - current array element
+* @returns accumulated result
+*/
+type BinaryReducer = ( acc: U, value: Complex128 ) => U;
+
+/**
+* Reducer function invoked for each element in an array.
+*
+* @param acc - accumulated result
+* @param value - current array element
+* @param index - current array element index
+* @returns accumulated result
+*/
+type TernaryReducer = ( acc: U, value: Complex128, index: number ) => U;
+
+/**
+* @param acc - accumulated result
+* @param value - current array element
+* @param index - current array element index
+* @param arr - array on which the method was called
+* @returns accumulated result
+*/
+type QuaternaryReducer = ( acc: U, value: Complex128, index: number, arr: Complex128Array ) => U;
+
+/**
+* Reducer function invoked for each element in an array.
+*
+* @param acc - accumulated result
+* @param value - current array element
+* @param index - current array element index
+* @param arr - array on which the method was called
+* @returns accumulated result
+*/
+type Reducer = NullaryReducer | UnaryReducer | BinaryReducer | TernaryReducer | QuaternaryReducer;
+
/**
* Class for creating a 128-bit complex number array.
*/
@@ -811,6 +865,35 @@ declare class Complex128Array implements Complex128ArrayInterface {
*/
map( fcn: MapFcn, thisArg?: ThisParameterType> ): Complex128Array;
+ /**
+ * Applies a provided callback function to each element of the array, in order, passing in the return value from the calculation on the preceding element and returning the accumulated result upon completion.
+ *
+ * @param reducer - callback function
+ * @param initialValue - initial value
+ * @returns accumulated result
+ *
+ * @example
+ * var real = require( '@stdlib/complex/real' );
+ * var imag = require( '@stdlib/complex/imag' );
+ * var cadd = require( '@stdlib/math/base/ops/cadd' );
+ *
+ * var arr = new Complex128Array( 3 );
+ *
+ * arr.set( [ 1.0, 1.0 ], 0 );
+ * arr.set( [ 2.0, 2.0 ], 1 );
+ * arr.set( [ 3.0, 3.0 ], 2 );
+ *
+ * var z = arr.reduce( cadd );
+ * // returns
+ *
+ * var re = real( z );
+ * // returns 6.0
+ *
+ * var im = imag( z );
+ * // returns 6.0
+ */
+ reduce( reducer: Reducer, initialValue?: U ): U;
+
/**
* Reverses an array in-place.
*
diff --git a/complex128/lib/main.js b/complex128/lib/main.js
index f3468c1d..70481104 100644
--- a/complex128/lib/main.js
+++ b/complex128/lib/main.js
@@ -1696,6 +1696,71 @@ setReadOnly( Complex128Array.prototype, 'map', function map( fcn, thisArg ) {
return out;
});
+/**
+* Applies a provided callback function to each element of the array, in order, passing in the return value from the calculation on the preceding element and returning the accumulated result upon completion.
+*
+* @name reduce
+* @memberof Complex128Array.prototype
+* @type {Function}
+* @param {Function} reducer - callback function
+* @param {*} [initialValue] - initial value
+* @throws {TypeError} `this` must be a complex number array
+* @throws {TypeError} first argument must be a function
+* @throws {Error} if not provided an initial value, the array must have at least one element
+* @returns {*} accumulated result
+*
+* @example
+* var real = require( '@stdlib/complex/real' );
+* var imag = require( '@stdlib/complex/imag' );
+* var cadd = require( '@stdlib/math/base/ops/cadd' );
+*
+* var arr = new Complex128Array( 3 );
+*
+* arr.set( [ 1.0, 1.0 ], 0 );
+* arr.set( [ 2.0, 2.0 ], 1 );
+* arr.set( [ 3.0, 3.0 ], 2 );
+*
+* var z = arr.reduce( cadd );
+* // returns
+*
+* var re = real( z );
+* // returns 6.0
+*
+* var im = imag( z );
+* // returns 6.0
+*/
+setReadOnly( Complex128Array.prototype, 'reduce', function reduce( reducer, initialValue ) {
+ var buf;
+ var acc;
+ var len;
+ var v;
+ var i;
+
+ if ( !isComplexArray( this ) ) {
+ throw new TypeError( 'invalid invocation. `this` is not a complex number array.' );
+ }
+ if ( !isFunction( reducer ) ) {
+ throw new TypeError( format( 'invalid argument. First argument must be a function. Value: `%s`.', reducer ) );
+ }
+ buf = this._buffer;
+ len = this._length;
+ if ( arguments.length > 1 ) {
+ acc = initialValue;
+ i = 0;
+ } else {
+ if ( len === 0 ) {
+ throw new Error( 'invalid operation. If not provided an initial value, an array must contain at least one element.' );
+ }
+ acc = getComplex128( buf, 0 );
+ i = 1;
+ }
+ for ( ; i < len; i++ ) {
+ v = getComplex128( buf, i );
+ acc = reducer( acc, v, i, this );
+ }
+ return acc;
+});
+
/**
* Reverses an array in-place.
*
diff --git a/complex128/test/test.reduce.js b/complex128/test/test.reduce.js
new file mode 100644
index 00000000..5f639944
--- /dev/null
+++ b/complex128/test/test.reduce.js
@@ -0,0 +1,212 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2023 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var tape = require( 'tape' );
+var hasOwnProp = require( '@stdlib/assert/has-own-property' );
+var isFunction = require( '@stdlib/assert/is-function' );
+var cadd = require( '@stdlib/math/base/ops/cadd' );
+var instanceOf = require( '@stdlib/assert/instance-of' );
+var real = require( '@stdlib/complex/real' );
+var imag = require( '@stdlib/complex/imag' );
+var Complex128 = require('@stdlib/complex/float64');
+var Complex128Array = require( './../lib' );
+
+
+// TESTS //
+
+tape( 'main export is a function', function test( t ) {
+ t.ok( true, __filename );
+ t.strictEqual( typeof Complex128Array, 'function', 'main export is a function' );
+ t.end();
+});
+
+tape( 'attached to the prototype of the main export is a `reduce` method', function test( t ) {
+ t.strictEqual( hasOwnProp( Complex128Array.prototype, 'reduce' ), true, 'has property' );
+ t.strictEqual( isFunction( Complex128Array.prototype.reduce ), true, 'has method' );
+ t.end();
+});
+
+tape( 'the method throws an error if invoked with a `this` context which is not a complex number array instance', function test( t ) {
+ var values;
+ var arr;
+ var i;
+
+ arr = new Complex128Array( 5 );
+
+ values = [
+ '5',
+ 5,
+ NaN,
+ true,
+ false,
+ null,
+ void 0,
+ {},
+ [],
+ function noop() {}
+ ];
+ for ( i = 0; i < values.length; i++ ) {
+ t.throws( badValue( values[i] ), TypeError, 'throws an error when provided '+values[i] );
+ }
+ t.end();
+
+ function badValue( value ) {
+ return function badValue() {
+ return arr.map.reduce( value, cadd );
+ };
+ }
+});
+
+tape( 'the method throws an error if provided a first argument which is not a function', function test( t ) {
+ var values;
+ var arr;
+ var i;
+
+ arr = new Complex128Array( 10 );
+
+ values = [
+ '5',
+ 3.14,
+ NaN,
+ true,
+ false,
+ null,
+ void 0,
+ {},
+ []
+ ];
+ for ( i = 0; i < values.length; i++ ) {
+ t.throws( badValue( values[i] ), TypeError, 'throws an error when provided '+values[i] );
+ }
+ t.end();
+
+ function badValue( value ) {
+ return function badValue() {
+ return arr.reduce( value );
+ };
+ }
+});
+
+tape( 'the method throws an error if not provided an initial value when operating on an empty complex number array', function test( t ) {
+ var arr;
+
+ arr = new Complex128Array( 0 );
+ t.throws( foo, Error, 'throws an error' );
+ t.end();
+
+ function foo() {
+ arr.reduce( cadd );
+ }
+});
+
+tape( 'the method uses the first element of the array as the initial value when an initial value is not provided', function test( t ) {
+ var valueArray;
+ var accArray;
+ var expected;
+ var actual;
+ var arr;
+
+ arr = new Complex128Array( [ 1.0, -1.0, 2.0, -2.0, 3.0, -3.0 ] );
+ accArray = [ 1.0, -1.0, 3.0, -3.0 ];
+ valueArray = [ 2.0, -2.0, 3.0, -3.0 ];
+ expected = new Complex128( 6.0, -6.0 );
+ actual = arr.reduce( reducer );
+
+ t.strictEqual( instanceOf( actual, Complex128 ), true, 'returns expected value' );
+ t.strictEqual( real( actual ), real( expected ), 'returns expected value' );
+ t.strictEqual( imag( actual ), imag( expected ), 'returns expected value' );
+
+ t.end();
+
+ function reducer( acc, value, index ) {
+ var ind = 2*(index-1);
+ t.strictEqual( instanceOf( acc, Complex128 ), true, 'returns expected value' );
+ t.strictEqual( real( acc ), accArray[ ind ], 'returns expected value' );
+ t.strictEqual( imag( acc ), accArray[ ind+1 ], 'returns expected value' );
+ t.strictEqual( instanceOf( value, Complex128 ), true, 'returns expected value' );
+ t.strictEqual( real( value ), valueArray[ ind ], 'returns expected value' );
+ t.strictEqual( imag( value ), valueArray[ ind+1 ], 'returns expected value' );
+ return cadd( acc, value );
+ }
+});
+
+tape( 'the method supports providing an initial value as the second argument', function test( t ) {
+ var valueArray;
+ var accArray;
+ var expected;
+ var actual;
+ var arr;
+
+ arr = new Complex128Array( [ 1.0, -1.0, 2.0, -2.0, 3.0, -3.0 ] );
+ accArray = [ 2.0, -2.0, 3.0, -3.0, 5.0, -5.0 ];
+ valueArray = [ 1.0, -1.0, 2.0, -2.0, 3.0, -3.0 ];
+ expected = new Complex128( 8.0, -8.0 );
+ actual = arr.reduce( reducer, new Complex128( 2.0, -2.0 ) );
+
+ t.strictEqual( instanceOf( actual, Complex128 ), true, 'returns expected value' );
+ t.strictEqual( real( actual ), real( expected ), 'returns expected value' );
+ t.strictEqual( imag( actual ), imag( expected ), 'returns expected value' );
+
+ t.end();
+
+ function reducer( acc, value, index ) {
+ t.strictEqual( instanceOf( acc, Complex128 ), true, 'returns expected value' );
+ t.strictEqual( real( acc ), accArray[ 2*index ], 'returns expected value' );
+ t.strictEqual( imag( acc ), accArray[ (2*index)+1 ], 'returns expected value' );
+ t.strictEqual( instanceOf( value, Complex128 ), true, 'returns expected value' );
+ t.strictEqual( real( value ), valueArray[ 2*index ], 'returns expected value' );
+ t.strictEqual( imag( value ), valueArray[ (2*index)+1 ], 'returns expected value' );
+ return cadd( acc, value );
+ }
+});
+
+tape( 'the method returns the accumulated result', function test( t ) {
+ var expected;
+ var actual;
+ var arr;
+
+ arr = new Complex128Array( [ 1.0, -1.0, 2.0, -2.0, 3.0, -3.0 ] );
+ expected = new Complex128( 6.0, -6.0 );
+ actual = arr.reduce( cadd );
+
+ t.strictEqual( instanceOf( actual, Complex128 ), true, 'returns expected value' );
+ t.strictEqual( real( actual ), real( expected ), 'returns expected value' );
+ t.strictEqual( imag( actual ), imag( expected ), 'returns expected value' );
+ t.end();
+});
+
+tape( 'the method supports returning real-valued results', function test( t ) {
+ var expected;
+ var actual;
+ var arr;
+
+ arr = new Complex128Array( [ 1.0, -1.0, 2.0, -2.0, 3.0, -3.0 ] );
+ expected = 6.0;
+ actual = arr.reduce( reducer, 0.0 );
+
+ t.strictEqual( actual, expected, 'returns expected value' );
+ t.end();
+
+ function reducer( acc, value ) {
+ return acc + real( value );
+ }
+});