excerpt function (See related posts)

    ;-- collect-based EXCERPT ----------------------------------
    ; Could also change EXTRACT to accept a block value for WIDTH
    ; (renamed to, e.g., SPEC).
    ; The dialect allows you to use commas in the block, but how they
    ; are interpreted is not how you might think. Coming after a number,
    ; they are a valid lexical form, but they denote a decimal! rather
    ; than being seen as a separator, which means you can't use them too
    ; flexibly.
    excerpt: func [
        {Returns the specified items and/or ranges from the series.}
        series  [series!]
        offsets [block!] {Offsets of the items to extract; dialected.}
        /only "return sub-block ranges as blocks"
        /local
            emit-range rules
            from* to* index*    ; parse vars
    ][
        ; always uses ONLY right now; it's a prototype.
        collect/only val [
            emit-range: func [start end] [
                start: to integer! start
                if number? end [end: to integer! end - start + 1]
                val: either end = 'end [copy at series start][
                    copy/part at series start end
                ]
            ]
            rules: [
                some [
                    opt 'from set from* number! 'to set to* number! (
                        emit-range from* to*
                    )
                  | opt 'from set from* number! 'to 'end (emit-range from* 'end)
                  | 'to set to* number! (emit-range 1 to*)
                  | set index* number!  (val: pick series index*)
                  | into rules
                ]
            ]
            parse offsets rules
        ]
    ]
    comment {
        b: [1 2 3 4 5 6 7 8 9 10 11 12 13 14]
        excerpt b [1 3 5]
        excerpt b [1 3 to 6 8]
        excerpt/only b [1, 3 to 6, 8]
        excerpt b [1 [5 to 7] 8]
        excerpt/only b [1 (from 5 to 7) 8]
        excerpt b [(to 2) [4 to 6] 8, 10, from 12 to end]
        excerpt/only b [to 2, 4 to 6, 8, 10, (12 to end)]
        ; Can't use a comma after 'end
        excerpt/only b [to 2 to 6 8 10 to end 12 to end]
        excerpt/only b [to 2, to 6, 8 [10 to end] 12 to end]
        excerpt/only trim {
            REBOL is my favorite language
        } [
            to 5, 10 to 11, 13, 14, 15, 22 to end
        ]
        excerpt/only to binary! {REBOL is my favorite language} [
            to 5, 10 to 11, 13, 14, 15, 22 to end
        ]
    }