How to resolve the algorithm First-class functions/Use numbers analogously step by step in the Go programming language

Published on 12 May 2024 09:40 PM
#Go

How to resolve the algorithm First-class functions/Use numbers analogously step by step in the Go programming language

Table of Contents

Problem Statement

In First-class functions, a language is showing how its manipulation of functions is similar to its manipulation of other types. This tasks aim is to compare and contrast a language's implementation of first class functions, with its normal handling of numbers.

Write a program to create an ordered collection of a mixture of literally typed and expressions producing a real number, together with another ordered collection of their multiplicative inverses. Try and use the following pseudo-code to generate the numbers for the ordered collections: Create a function multiplier, that given two numbers as arguments returns a function that when called with one argument, returns the result of multiplying the two arguments to the call to multiplier that created it and the argument in the call: Applying the multiplier of a number and its inverse from the two ordered collections of numbers in pairs, show that the result in each case is one. Compare and contrast the resultant program with the corresponding entry in First-class functions. They should be close. To paraphrase the task description: Do what was done before, but with numbers rather than functions

Let's start with the solution:

Step by Step solution about How to resolve the algorithm First-class functions/Use numbers analogously step by step in the Go programming language

Explanation

The Go code you provided demonstrates the use of closures and interfaces to create a flexible and versatile set of functions that can perform calculations on a list of numbers. Let's break it down step by step:

First Code Block

  1. Variables and Closures:

    • We define variables x, xi, y, yi, z, and zi as floating-point numbers.
    • We create a slice numbers containing x, y, and z, and a slice inverses containing their reciprocals (xi, yi, and zi).
    • We define a function multiplier that takes two float64 arguments and returns a function that multiplies its argument by the product of the input arguments.
    • We iterate through the numbers and inverses slices and create a slice mfs of functions that perform the multiplication using the multiplier function.
  2. Evaluation (point C):

    • We then iterate through the mfs slice and call each function with an argument of 1.0 to evaluate and print the results.

Second Code Block

  1. Variables and Interfaces:

    • Similar to the first block, we define variables x, xi, y, yi.
    • Instead of using anonymous functions for z and zi, we define them as functions that return the same values as before.
    • We create two slices, numbers and inverses, but this time they contain a mix of float64 values, pointers to float64 values, and functions that return float64 values.
  2. Closure and Interface Invocation:

    • We create a slice mfs of functions that take one interface{} argument and return a float64 value.
    • The multiplier function takes two interface{} arguments and returns a function that multiplies its argument by the evaluation of the two input arguments.
    • We iterate through the numbers and inverses slices and create a slice mfs of functions that perform the multiplication using the multiplier function.
  3. Evaluation (point C):

    • We then iterate through the mfs slice and call each function with an argument of 1.0.
    • Inside the multiplier function, we use the eval function to evaluate the three interface{} arguments (n1, n2, and m) as float64 values and then perform the multiplication.
  4. Utility Function eval:

    • The eval function evaluates an interface{} value and returns a float64 value.
    • It checks the type of the interface{} value and returns the appropriate floating-point value.

Key Concepts:

  1. Closures: Functions that can access variables from their enclosing scope, even after the function returns. This allows us to create functions that depend on the values of variables in the outer scope.
  2. Interfaces: In Go, interfaces represent a contract that types can implement. They allow us to create functions that can operate on different types that satisfy the same interface.
  3. Reflection: The reflect package allows us to examine and manipulate values and types at runtime. In this case, we use it to evaluate interface{} values as float64 values.

By leveraging these concepts, this code provides a flexible way to define and invoke functions that can perform different operations on a variety of data types.

Source code in the go programming language

package main

import "fmt"

func main() {
    x := 2.
    xi := .5
    y := 4.
    yi := .25
    z := x + y
    zi := 1 / (x + y)
    // point A

    numbers := []float64{x, y, z}
    inverses := []float64{xi, yi, zi}
    // point B

    mfs := make([]func(float64) float64, len(numbers))
    for i := range mfs {
        mfs[i] = multiplier(numbers[i], inverses[i])
    }
    // point C

    for _, mf := range mfs {
        fmt.Println(mf(1))
    }
}

func multiplier(n1, n2 float64) func(float64) float64 {
    // compute product of n's, store in a new variable
    n1n2 := n1 * n2
    // close on variable containing product
    return func(m float64) float64 {
        return n1n2 * m
    }
}


package main

import "fmt"

func main() {
    x := 2.
    xi := .5
    y := 4.
    yi := .25
    z := func() float64 { return x + y }
    zi := func() float64 { return 1 / (x + y) }
    // point A

    numbers := []interface{}{&x, &y, z}
    inverses := []interface{}{&xi, &yi, zi}
    // point B

    mfs := make([]func(n interface{}) float64, len(numbers))
    for i := range mfs {
        mfs[i] = multiplier(numbers[i], inverses[i])
    }
    // pointC

    for _, mf := range mfs {
        fmt.Println(mf(1.))
    }
}

func multiplier(n1, n2 interface{}) func(interface{}) float64 {
    return func(m interface{}) float64 {
        // close on interface objects n1, n2, and m
        return eval(n1) * eval(n2) * eval(m)
    }
}

// utility function for evaluating multiplier interface objects
func eval(n interface{}) float64 {
    switch n.(type) {
    case float64:
        return n.(float64)
    case *float64:
        return *n.(*float64)
    case func() float64:
        return n.(func() float64)()
    }
    panic("unsupported multiplier type")
    return 0 // never reached
}


  

You may also check:How to resolve the algorithm Greyscale bars/Display step by step in the Eiffel programming language
You may also check:How to resolve the algorithm Search a list step by step in the Groovy programming language
You may also check:How to resolve the algorithm Symmetric difference step by step in the Miranda programming language
You may also check:How to resolve the algorithm Assertions step by step in the Erlang programming language
You may also check:How to resolve the algorithm Number reversal game step by step in the Forth programming language