#  (C) Copyright David Abrahams 2001. 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.

#
#   Returns a list of the following substrings:
#   1) from beginning till the first occurence of 'separator' or till the end,
#   2) between each occurence of 'separator' and the next occurence,
#   3) from the last occurence of 'separator' till the end.
#   If no separator is present, the result will contain only one element.
#
rule split ( string separator )
{
    local result ;
    local s = $(string) ;

    # Break pieaces off 's' until it has no separators left.
    local match = 1 ;
    while $(match)
    {
        match = [ MATCH ^(.*)($(separator))(.*) : $(s) ] ;
        if $(match) {
            match += "" ; # in case 3rd item was empty - works around MATCH bug
            result = $(match[3]) $(result) ;
            s = $(match[1]) ;
        }
    }
    # Combine the remaining part at the beginning, which does not have
    # separators, with the pieces broken off.
    # Note that rule's signature does not allow initial s to be empty.
    return $(s) $(result) ;
}

# Match string against pattern, and return the elements indicated by
# indices.
rule match ( pattern : string : indices * )
{
    indices ?= 1 2 3 4 5 6 7 8 9 ;
    local x = [ MATCH $(pattern) : $(string) ] ;
    return $(x[$(indices)]) ;
}

rule __test__ ( )
{
    import assert ;

    assert.result a b c : split "a/b/c" / ;
    assert.result "" a b c : split "/a/b/c" / ;
    assert.result "" "" a b c : split "//a/b/c" / ;
    assert.result "" a "" b c : split "/a//b/c" / ;
    assert.result "" a "" b c "" : split "/a//b/c/" / ;
    assert.result "" a "" b c "" "" : split "/a//b/c//" / ;
    
    assert.result a c b d
      : match (.)(.)(.)(.) : abcd : 1 3 2 4 ;
    
    assert.result a b c d
      : match (.)(.)(.)(.) : abcd ;
    
    assert.result ababab cddc
      : match ((ab)*)([cd]+) : abababcddc : 1 3 ;
}