left-pad

8.16.0.4

left-pad🔗ℹ

Examples:

> (require left-pad)
> (left-pad "foo" 5)
" foo"
> (left-pad "foobar" 6)
"foobar"
> (left-pad 17 5 0)
"00017"

procedure
(left-pad value pad-width [pad-value]) → string?
  value : any/c
  pad-width : exact-positive-integer?
  pad-value : " " = any/c

Converts value to a string in display mode, then pads it with copies of pad-value (after coercing pad-value to a string) until the result has length pad-width.

Returns the same result as:

(~a value #:align 'right
#:min-width pad-width
#:left-pad-string (~a pad-value))

except that it can be faster (or slower — it’s currently slower).

The preconditions of left-pad are:

The display-mode representation of value has at most pad-width characters.
The display-mode representation of pad-value has exactly 1 character.

The postconditions of left-pad are:

Returns a string with pad-width characters.
The display-mode representation of value is a suffix of the result string.
The result is left-padded with copies of (the display-mode representation of) pad-value.

The pre- and post-conditions are enforced by a badass dependent contract.

1 Typed Racket API🔗ℹ

(require left-pad/typed)

package: left-pad

value
left-pad : (->* [Any Integer] [Any] String)