• via Digitalmars-d-bugs (35/35) Aug 31 2014 https://issues.dlang.org/show_bug.cgi?id=13409

via Digitalmars-d-bugs <digitalmars-d-bugs puremagic.com> writes:

https://issues.dlang.org/show_bug.cgi?id=13409

          Issue ID: 13409
           Summary: std.range.padLeft/Right
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: Phobos
          Assignee: nobody puremagic.com
          Reporter: peter.alexander.au gmail.com

Would be useful to have two new higher-order ranges in std.range:

padLeft(R, E)(R r, E e, size_t n)
  if (isInputRange!R &&
      hasLength!R &&
      !is(CommonType!(ElementType!R, E) == void))

padRight(R, E)(R r, E e, size_t n)
  is (isInputRange!R &&
      !is(CommonType!(ElementType!R, E) == void))

padLeft returns a range that is padded on the left up to 'n' elements with 'e',
and padRight pads on the right.

Example:

int[] a = [1, 2, 3];
padLeft(a, 0, 5) == [0, 0, 1, 2, 3]
padRight(a, 0, 5) == [1, 2, 3, 0, 0]

Notes:
* If r.length >= n then neither add any padding, and just iterates r.
* padLeft requires hasLength, but padRight does not.
* If R is forward, then so will padLeft/Right
* If R is bidirectional, and hasLength, then so will padLeft/Right
* If R is random access, and hasLength, then so will padLeft/Right
* If R is infinite, padLeft/Right will return r and be type R.

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