String processing

In a grammar rule, as whitespace/0, represents whitespace (a positive number of space (32), tab (9), newline (10) or return (13) characters). Thus, Rest is a proper suffix of String with one or more whitespace characters removed. An example of use would be:

   attrs([]) --> ""
   attrs([N|Ns]) -->
       whitespace,
       attr(N),
       attrs(Ns).

Usage:whitespace(S1,S2)

• The following properties should hold at call time:
  (basic_props:string/1)S1 is a string (a list of character codes).
• The following properties should hold upon exit:
  (basic_props:string/1)S2 is a string (a list of character codes).

In a grammar rule, as whitespace0/0, represents possible whitespace (any number of space (32), tab (9), newline (10) or return (13) characters). Thus, Rest is String or a proper suffix of String with one or more whitespace characters removed. An example of use would be:

   assignment(N,V) -->
       variable_name(N), whitespace0, "=", whitespace0, value(V).

Usage:whitespace0(S1,S2)

• The following properties should hold at call time:
  (basic_props:string/1)S1 is a string (a list of character codes).
• The following properties should hold upon exit:
  (basic_props:string/1)S2 is a string (a list of character codes).

In a grammar rule, as string/1, represents literally String. An example of use would be:

double(A) -->
    string(A),
    string(A).

Usage 1:

• Call and exit should be compatible with:
  (basic_props:string/1)String is a string (a list of character codes).
  (basic_props:string/1)Head is a string (a list of character codes).
  (basic_props:string/1)Tail is a string (a list of character codes).
• The following properties should hold upon exit:
  (basic_props:string/1)String is a string (a list of character codes).
  (basic_props:string/1)Head is a string (a list of character codes).
  (basic_props:string/1)Tail is a string (a list of character codes).

Usage 2:string(A,B,C)

• The following properties should hold at call time:
  (basic_props:list/1)C is a list.
• The following properties should hold upon exit:
  (basic_props:list/1)A is a list.
  (basic_props:list/1)B is a list.