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Feature #15945

open

Option to truncate in `String#ljust`, `String#rjust`, and `String#center`

Added by sawa (Tsuyoshi Sawada) almost 2 years ago. Updated almost 2 years ago.

Status:
Open
Priority:
Normal
Assignee:
-
Target version:
-
[ruby-core:93275]

Description

Sometimes, I need to adjust a string to an exact length: Pad if shorter, and truncate if longer. To do that, I need to combine two methods like this:

"12".ljust(5, "*")[0, 5]        # => "12***"
"1234567".ljust(5, "*")[0, 5]   # => "12345"

"xyz".rjust(5, "*")[-5, 5]      # => "**xyz"
"stuvwxyz".rjust(5, "*")[-5, 5] # => "vwxyz"

But that is messy, and needs a bit of thinking. It becomes even harder with centering.

I request an option on String#ljust, String#rjust, String#center to truncate the string when it is longer than the given length.

One way to do so may be: take a keyword :truncate or :trunc.

"12".ljust(5, "*", trunc: true)       # => "12***"
"1234567".ljust(5, "*", trunc: true)  # => "12345"

"xyz".rjust(5, "*", trunc: true)      # => "**xyz"
"stuvwxyz".rjust(5, "*", trunc: true) # => "vwxyz"

"abc".center(5, "*", trunc: true)     # => "*abc*"
"abcdefg".center(5, "*", trunc: true) # => "bcdef"

Another way is, when the length is negative, interpret it as truncating option.

"12".ljust(-5, "*")       # => "12***"
"1234567".ljust(-5, "*")  # => "12345"

"xyz".rjust(-5, "*")      # => "**xyz"
"stuvwxyz".rjust(-5, "*") # => "vwxyz"

"abc".center(-5, "*")     # => "*abc*"
"abcdefg".center(-5, "*") # => "bcdef"

But the second way changes the current behavior.

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