Mini calculator

Here is the shorter calculator code on earth and intelligible!

Here is the source code:

REBOL [
    Title: "Mini-Calculator"
    Date: 6-Mar-2002
    Version: 1.1.3
    File: %mini-calc.r
    Author: "Ryan Cole"
    Purpose: "Tiny calculator example."
    Email: ryancole@usa.com
]
reg: []
op: no

do solve: does [
    acc: none
    if op [error? try [acc: do reform [any [reg/2 acc 0] op 'to-decimal reg/1]]]
    reg: copy []
    op: no
]
calc: func [key] [
    if find ".0123456789" key [
        if none? pick reg not op [insert reg copy ""]
        if not all ["." = key   find reg/1 key] [append reg/1 key]
    ]
    if find "+-*/" key [
        if reg/2 [solve]
        any [reg/1 insert reg any [acc 0]]
        op: key
    ]
    if key = "=" [solve]
]
view layout [
    origin 0x0 space 0x0 across
    lcd: field "0." silver 140x22 right feel none
    return
    style k button 35x25 [
        calc face/text
        if not find lcd/text: form any [reg/1 acc 0] "." [append lcd/text "."]
        show lcd
    ]
    k "7" k "8" k "9" k "/" return
    k "4" k "5" k "6" k "*" return
    k "1" k "2" k "3" k "-" return
    k "0" k "." k "=" k "+"
]