diff options
Diffstat (limited to 'src/boot/utility.boot')
| -rw-r--r-- | src/boot/utility.boot | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/src/boot/utility.boot b/src/boot/utility.boot index bde1090b..6527a07a 100644 --- a/src/boot/utility.boot +++ b/src/boot/utility.boot @@ -34,7 +34,7 @@ import initial_-env namespace BOOTTRAN module utility (objectMember?, symbolMember?, stringMember?, charMember?, scalarMember?, listMember?, reverse, reverse!, - lastNode, append!, copyList) + lastNode, append!, copyList, substitute, substitute!) --% membership operators @@ -133,3 +133,24 @@ append!(x,y) == y = nil => x lastNode(x).rest := y x + +--% substitution + +substitute!(y,x,s) == + s = nil => nil + sameObject?(x,s) => y + if cons? s then + s.first := substitute!(y,x,first s) + s.rest := substitute!(y,x,rest s) + s + +substitute(y,x,s) == + s = nil => nil + sameObject?(x,s) => y + cons? s => + h := substitute(y,x,first s) + t := substitute(y,x,rest s) + sameObject?(h,first s) and sameObject?(t,rest s) => s + [h,:t] + s + |