String padding functions

[Piotr Zurek]

Hello,

I think I may have found something that should make a nice simple way to contribute something small but possibly to this brilliant language.

Go's standard library seems to be missing functions allowing to pad a string with a another string up to a certain number of characters.

Something like C#'s PadLeft, PadRight (http://msdn.microsoft.com/en-us/library/66f6d830(v=vs.110).aspx) or Ruby's ljust, rjust (http://www.ruby-doc.org/core-2.0.0/String.html#method-i-ljust).

I have implemented those for my own purposes but maybe the general public will find those useful too?

I have found those especially useful when implementing sequential numbering that needs to return a certain number of characters, for file names like file_001.txt or dates 2013-02-08.

My implementation looks like that:

func PadLeft(s, p string, l int) string

func PadRight(s, p string, l int) string

and I was also thinking about writing :

func Pad(s, p string, l int) string

The way they work, they take a string 's' and pad it with 'p' up to the total number of 'l'. PadLeft adds characters on the left, PadRight obviously on the right and Pad could put 's' in the middle and pad it on both sides.

Do you guys think it would be valuable additions to the 'strings' package?

Cheers,

Piotr

[Egon Elbre]

fmt already can do most of that... http://play.golang.org/p/enMD71zFg4

+ egon

[Oleku Konko]

I might be wrong but i don't think `fmt` has proper support or simplicity when it comes to string padding  because its only easy padding with `space` and `0` anything else introduces complexity 

If i understand Zurek he is trying to implement something like :

package main
import "fmt"
func PadRight(str, pad string, lenght int) string {
    for {
        str += pad
        if len(str) > lenght {
            return str[0:lenght]
        }
    }
}
func PadLeft(str, pad string, lenght int) string {
    for {
        str = pad + str
        if len(str) > lenght {
            return str[0:lenght]
        }
    }
}
func main() {
    str := "abc"
    fmt.Println(PadRight(str, "x", 5))   // expects abcxx
    fmt.Println(PadLeft(str, "x", 5))    // expects xxabc
    fmt.Println(PadRight(str, "xyz", 5)) // expects abcxy
    fmt.Println(PadLeft(str, "xyz", 5))  // expects xyzab
}

See : http://play.golang.org/p/zciRZvD0Gr

[Egon Elbre]

Yes I'm aware of that... (hence the word "most of that")... But, I rarely have seen something that requires padding numbers with anything else and similarly for strings. If I have seen something like that, then it's more complex... e.g. "(000)_000-0000;0;*". Those PadRight/PadLeft are for special uses and not generally useful.

+ egon

[Lucy hi]

On Sunday, 22 December 2013 09:54:23 UTC+1, Egon Elbre wrote:

fmt already can do most of that... http://play.golang.org/p/enMD71zFg4

+ egon

 

Dynamic padding is rather painful if you try using fmt for it as well.

[Brad Fitzpatrick]

I don't think these come up often enough to warrant inclusion in the standard library.

For example. I can't think of anything in the standard library that would use these.

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[Piotr Zurek]

On Monday, December 23, 2013 5:49:09 AM UTC+13, Brad Fitzpatrick wrote:

I don't think these come up often enough to warrant inclusion in the standard library.

For example. I can't think of anything in the standard library that would use these.

Fair enough. I'll have to come up with a better idea for my first contribution.

[Robert Griesemer]

You may also want to look at text/tabwriter which provides some mechanism to write columns in tabular form, with left or right alignment, and with different filler characters.

- gri

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