# Range utilities

This unit lives at [mem/range.fs] and provides a few range related words.

## API

intersect[] ( a1 u1 a2 u2 -- ?a u )
  Compute the intersection between the two given ranges and return the part
  common to both. If there is no intersection, u=0 and a isn't present.

glue[] ( a1 u1 a2 u2 -- a u )
  Glue two ranges together, yielding the smallest possible range that include
  them both. If one of the ranges has a zero length, the "other range is yielded
  as is.

?[] ( a u -- ?a ?u f )
  If u=0, yield f=0 with "a" and "u" absent. Otherwise, yield f=1 and "a" and
  "u" present and unchanged.

cmove- ( src dst u -- )
  Like "cmove", but operates backwards. You'll want to use this when copying
  overlapping memory area "forward" (dst > src).

rslide+ ( by a u -- )
  Move range "a u" forward in memory by "by" bytes.

rslide- ( by a u -- )
  Move range "a u" backward in memory by "by" bytes.

ltrim[] ( a u n -- a u )
  Trim "n" characters at the left of range "a u" and return the resulting range.

rtrim[] ( a u n -- a u )
  Trim "n" characters at the right of range "a u" and return the resulting
  range.

swap[] ( a u -- )
wswap[] ( a u -- )
cswap[] ( a u -- )
  Reverse the order of the elements in the range. For example, a range with
  3 elements "1 2 3" becomes a range with elements "3 2 1".

split[] ( a u idx -- alo ulo ahi uhi )
  Split range "a u" at index "idx", thus yielding "a idx a+idx u-idx".

  If idx >= u, yields "a u a+u 0".