Golang Scratch Notes

Assignment + Declaration vs assignment

`:=`

TODO: Confirm this statement

Using this operator results in a declaration (automatically I believe) and initial assignment. You can't go back later and use the operator again to assign a different value to the variable.

`=`

TODO: Confirm this statement

This is an assignment operator. This is used to assign a value to a variable that has been previously declared.

Specify source file as the startup file for the application

package main (declaration that it is the main package)
main() function without arguments

Single quotes vs Double quotes

Single quotes designate a byte, rather than a string

Example from "Getting input from the console" (from Learning Go @ Lynda.com)

reader := bufio.NewReader(os.Stdin)
fmt.Print("Enter text: ")
str, _ := reader.ReadString('\n')

Parse functions do not automatically trim spaces

They also tend to fail if you do not trim them first.

Example code:

package main

import (
    "fmt"
    "bufio"
    "os"
    "strconv"
)

func main() {
    
    // var s string
    // fmt.Scanln(&s)
    // fmt.Println(s)

    reader := bufio.NewReader(os.Stdin)
    fmt.Print("Enter text: ")
    str, _ := reader.ReadString('\n')
    fmt.Println(str)
    
    fmt.Print("Enter a number: ")
    str, _ = reader.ReadString('\n')
    f, err := strconv.ParseFloat(str, 64)
    if err != nil {
        fmt.Println(err)
    } else {
        fmt.Println("Value of number:", f)
    }
}

This results in this error: strconv.ParseFloat: parsing "45\r\n": invalid syntax

Fix:

Import strings package
Call strings.TrimSpace() on str variable

Example snippet:

    fmt.Print("Enter a number: ")
    str, _ = reader.ReadString('\n')
    f, err := strconv.ParseFloat(strings.TrimSpace(str), 64)
    if err != nil {
        fmt.Println(err)
    } else {
        fmt.Println("Value of number:", f)
    }

By trimming the spaces, the strconv.ParseFloat() function succeeds.

deoren/golang_scratch_notes.md