operator - operators as functions

go get -u "tawesoft.co.uk/go"

import "tawesoft.co.uk/go/operator"

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Please migrate to https://github.com/tawesoft/golib (when available) instead.

Most programs relying on a package in this monorepo, such as the dialog or lxstrconv packages, will continue to work for the foreseeable future.

Rarely used packages have been hidden for now - they are in the git commit history at https://github.com/tawesoft/go if you need to resurrect one.

About

Package operator implements logical, arithmetic, bitwise and comparison operators as functions (like the Python operator module). Includes unary, binary, and n-ary functions with overflow checked variants.

Examples

Using operators as function arguments

package main

import (
    "fmt"
    "tawesoft.co.uk/go/operator"
)

func foo(op func(int, int) int, a int, b int) int {
    return op(a, b)
}

func fooChecked(op func(int8, int8) (int8, error), a int8, b int8) (int8, error) {
    return op(a, b)
}

func main() {
    fmt.Println(foo(operator.Int.Binary.Add, 5, 3))
    fmt.Println(foo(operator.Int.Binary.Sub, 5, 3))
    
    var result, err = fooChecked(operator.Int8Checked.Binary.Add, 126, 2) // max int8 is 127!
    if err != nil {
        fmt.Printf("error: %v (expected!)\n", err)
    } else {
        fmt.Println(result)
    }
}

Using operators in lookup tables for a command-line calculator program

package main

import (
    "bufio"
    "fmt"
    "os"
    "strconv"
    "strings"
    
    "tawesoft.co.uk/go/operator"
)

type checkedOperation func(float64, float64) (float64, error)

var reader = bufio.NewReader(os.Stdin)

var operations = map[string]checkedOperation {
    "+": operator.Float64Checked.Binary.Add,
    "-": operator.Float64Checked.Binary.Sub,
    "*": operator.Float64Checked.Binary.Mul,
    "/": operator.Float64Checked.Binary.Div,
}

func getNumber(prompt string) float64 {
    for {
        fmt.Print(prompt)
        var text, _ = reader.ReadString('\n')
        var result, err = strconv.ParseFloat(strings.TrimSpace(text), 64)
        if err != nil {
            fmt.Println("Sorry, try again. (%v)", err)
            continue
        }
        return result
    }
}

func getOperation(prompt string) checkedOperation {
    for {
        fmt.Print(prompt)
        var text, _ = reader.ReadString('\n')
        var operator, ok = operations[strings.TrimSpace(text)]
        if !ok {
            fmt.Println("Sorry, try again.")
            continue
        }
        return operator
    }
}

func main() {
    var firstNumber = getNumber("Enter a number (then press enter): ")
    var operation = getOperation("Enter +, -, * or / (then press enter) for add, subtract, multiply, or divide: ")
    var secondNumber = getNumber("Enter another number (then press enter): ")
    var result, err = operation(firstNumber, secondNumber)
    if err != nil {
        fmt.Printf("Sorry, something went wrong: %v\n", err)
    } else {
        fmt.Printf("The result is %.2f!\n", result)
    }
}

Getting Help

This package is part of tawesoft.co.uk/go, a monorepo for small Go modules maintained by Tawesoft®. Check out that URL for more information about other Go modules from Tawesoft plus community and commercial support options.