Diesel表达式-在分隔符后选择正确的值-

/*                               D I E S E L
 
       Dumb Interpretively Evaluated String Expression Language
 
    This "Dumb Interpretively Executed String Expression Language" is  the
    kernel  of        a  macro  language  you can customise by adding C code and
    embedding it into your program.
 
    It is short, written in portable C, and is readily integrated into any
    program.   It  is  useful  primarily  to  programs        which  need a very
    rudimentary macro expansion facility without the complexity of a  full
    language such as Lisp or FORTH.
 
    DIESEL  copies  its  input        directly  to  the  output  until  a  macro
    character, "$" or quoted string is encountered.  Quoted strings may be
    used  to  suppress        evaluation  of sequences of characters which would
    otherwise be interpreted as macros.  Quote marks may  be  included        in
    quoted strings by two adjacent quote marks.  For example:
 
        "$(if,1,True,False)="""$(if,1,True,False)""""
 
    Status  retrieval,        computation,  and  display are performed by DIESEL
    functions.        The available  functions  are  as  follows.   User-defined
    functions  are  not  implemented;  what  you  see  is  all you've got.
    Naturally, if  you        embed  DIESEL  in  your  application,  you'll  add
    functions  that  provide access to information and actions within your
    own program.  DIESEL's arithmetic  functions  accept  either  floating
    point  or  integer arguments, and perform all calculations in floating
    point.
 
    DIESEL String Functions
    -----------------------
 
    $(+,,,...)
        The  sum  of  the  numbers , , ... is returned.
 
    $(-,,,...)
        The  result  of subtracting the numbers  through  from
         is returned.
 
    $(*,,,...)
        The result of multiplying the numbers  ,,...        is
        returned.
 
    $(/,,,...)
        The  result of dividing the number  by ,...   is
        returned.
 
    $(=,,)
        If the        numbers    and    are  equal  1  is  returned,
        otherwise 0 is returned.
 
    $(,)
        If  the number  is less than  1 is returned, otherwise
        0 is returned.
 
    $(>,,)
        If the number    is  greater  than    1  is  returned,
        otherwise 0 is returned.
 
    $(!=,,)
        If  the  numbers    and   are not equal 1 is returned,
        otherwise 0 is returned.
 
    $(,)
        If the number   is  less        than  or  equal  to    1        is
        returned, otherwise 0 is returned.
 
    $(>=,,)
        If  the  number    is  greater  than or equal to  1 is
        returned, otherwise 0 is returned.
 
    $(AND,,,...)
        The bitwise logical AND of the integers  through                is
        returned.
 
    $(EQ,,)
        If the strings  and   are  identical  1  is  returned,
        otherwise 0.
 
    $(EVAL,)
        The  string  is passed to the DIESEL evaluator and the result
        of evaluating it is returned.
 
    $(FIX,)
        The real number  is truncated to an integer  by        discarding
        any fractional part.
 
    $(IF,,,)
        If    is        nonzero,    is        evaluated  and         returned.
        Otherwise,    is  evaluated  and returned.  Note that the
        branch not chosen by  is not evaluated.
 
    $(INDEX,,)
         is assumed to contain one or more values delimited by the
        macro argument separator character, comma.   selects one of
        these values to be extracted, with the first item  numbered  zero.
 
    $(NTH,,,,)
        Evaluates  and        returns  the  argument        selected  by  .        If
         is 0,  is returned, and so on.  Note the        difference
        between  $(NTH)  and  $(INDEX);  $(NTH) returns one of a series of
        arguments to the function while $(INDEX) extracts a value  from  a
        comma-delimited string passed as a single argument.  Arguments not
        selected by  are not evaluated.
 
    $(OR,,,...)
        The  bitwise  logical  OR of the integers  through  is
        returned.
 
    $(STRFILL,,)
        Returns the result of concatenating  of .
 
    $(STRLEN,)
        Returns the length of  in characters.
 
    $(SUBSTR,,,)
        Returns  the  substring  of  starting at character 
        and extending for  characters.        Characters in  the  string
        are numbered from 1.  If  is omitted, the entire remaining
        length of the string is returned.
 
    $(UPPER,)
        The   is returned converted to upper case according to the
        rules of the current locale.
 
    $(XOR,,,...)
        The bitwise logical XOR of the integers  through                is
        returned.
...
*/

$(if,$(eq,-,$(substr,$(getvar,dwgname),$(-,$(strlen,$(getvar,dwgname)),6),1)),
    $(substr,$(getvar,dwgname),$(-,$(strlen,$(getvar,dwgname)),5),2),
    $(if,$(eq,-,$(substr,$(getvar,dwgname),$(-,$(strlen,$(getvar,dwgname)),5),1)),
        $(substr,$(getvar,dwgname),$(-,$(strlen,$(getvar,dwgname)),4),1),
        0
     )
 )

$(substr,$(getvar,dwgname),$(-,$(strlen,$(getvar,dwgname)),5),2)