#  (C) Copyright David Abrahams 2002. Permission to copy, use, modify, sell and
#  distribute this software is granted provided this copyright notice appears in
#  all copies. This software is provided "as is" without express or implied
#  warranty, and with no claim as to its suitability for any purpose.

rule chars ( string )
{
    local result ;
    while $(string)
    {
        local s = [ SUBST $(string) (.?)(.?)(.?)(.?)(.?)(.?)(.?)(.?)(.*)
                        $9 $1 $2 $3 $4 $5 $6 $7 $8 ] ;
        string = $(s[1]) ;
        result += $(s[2-]) ;
    }
    
    # trim off empty strings
    while $(result[1]) && ! $(result[-2])
    {
        result = $(result[1--2]) ;
    }
    
    return $(result) ;
}

rule join ( strings * : separator ? )
{
    separator ?= "" ;
    local result = $(strings[1]) ;
    for local x in $(strings[2-])
    {
        result = $(result)$(separator)$(x) ;
    }
    return $(result) ;
}

rule __test__ ( )
{
    import assert ;
    assert.result a b c : chars abc ;
    
    # check boundary cases
    assert.result a : chars a ;
    assert.result : chars "" ;
    assert.result a b c d e f g h : chars abcdefgh ;
    assert.result a b c d e f g h i : chars abcdefghi ;
    assert.result a b c d e f g h i j : chars abcdefghij ;
    assert.result a b c d e f g h i j k : chars abcdefghijk ;
    
    assert.result a//b/c/d : join a "" b c d : / ;
    assert.result abcd : join  a "" b c d ;
}