Lua add a variable amount of characters to String

Question

I want to add an amount characters to a print, that equals space.

if #input >= 1 then
  for var=1, #input, 1 do
    [...]
    av = "was sent"

    else
      av = "doesn't exist"
    end

    space = 20-string.len(input[var])
    print(var..". '"..input[var].."' "..space..av)
  end
return
end

my goal is to align av vertically. input[var]varies in length.

Answer 1

Assuming you know that 20 is a maximum length of input[var] as your snippet implies, you can directly proceed to padding.

The straightforward solution would be to use string.rep:

print(var..". '"..input[var].."' ".. (" "):rep(space)..av)

string.format also allows adding padding left and right; using -x you can add left padding:

print(("%s. %-22s %s"):format(var, "'" .. input[var] .. "'", av))

Note that I've bumped the padding to 22 since the two single quotes are now included in the calculation.

---

How not to do it:

Bad: Quadratic runtime, many garbage strings, more complex / longer code

local padding = ""
for i = 1, space do padding = padding .. " " end

Bad: More overhead, garbage table, more complex / longer code

local t = {}
for i = 1, space do t[i] = " " end
local padding = table.concat(t)

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Side note: If input[var] is guaranteed to be a string, you can use #input[var] instead of string.len(input[var]).