Effect A specified offset or length is directly appended to either the dobj descriptor of the data object, an <(><<)>fs> field symbol, or a dereferenced data reference variable dref->*: Offsets/lengths can be specified for:
Elementary byte-like data objects
Elementary character-like data objects
Flat structures, whereby one of the following prerequisites must be satisfied in Unicode programs:
The structure contains flat character-like components only.
The first Unicode fragment of the structure is flat and character-like, and the substring addressed by specifying the offset and length is located within this fragment. The following restrictions apply:
In write positions, only flat data objects are permitted; it is not possible to write to substrings of strings.
Access to substrings of strings is also not possible in the following reader positions:
dobj[+off][(len)] specified as a memory area mem_area of the statement ASSIGN.
dobj[+off][(len)] specified as an argument of the statement GET REFERENCE or the reference operator REF.
dobj[+off][(len)] specified as an actual parameter for input parameters in calls of methods, function modules, and subroutines.
Offsets/lengths cannot be specified for literals or text symbols.
In the case of dynamically specified operands in parentheses, no lengths can be specified.
A dereferenced data reference variable dref->* must be typed in full.
For a writable expression, offsets/lengths cannot be specified as memory areas in the statement ASSIGN or as arguments of the reference operator REF (table expressions only). The segment of the data object is used that has the offset specified in off and the length (in characters or bytes) specified in len . A memory area must not be addressed outside the field boundaries, except in the case of the ASSIGN statement. For an offset specified without a length, the entire substring is addressed as of the off character; for a length specified without an offset, the first len characters are addressed (different rules apply to the ASSIGN statement). The operands off and len expect data objects of the type i. These data objects must contain positive integers, with the following exceptions.
The length 0 can be specified for strings.
A negative offset (but never length 0) can be specified if an <(> <<)>fs> field symbol is specified in the ASSIGN statement for dobj.
If off is smaller than the length of dobj, an asterisk ( *) can be specified for len. The upper limit of dobj then determines the upper limit of the memory area. If the prerequisites are not met or if the subarea defined by off and len is not completely contained in the data object (except in the case of ASSIGN), a syntax error occurs (if statically identifiable). Otherwise, an exception of class CX_SY_RANGE_OUT_OF_BOUNDS occurs. If off is specified as a numeric literal, then this literal cannot be prefixed with a sign. The offset and length specified are counted in characters for character-like data objects and in bytes for all other data objects. A character is equivalent to a byte in non- Unicode systems. A substring specified by an offset or length is handled like a data object of the specified length for which the data type depends on the data type of the original data object, the field symbol, or the data reference variable, as shown below: Original data typeData type of substring cc dn nn tn stringstring xx xstringxstring Structure typec If the length of the substring exactly corresponds to the length of the structure in a substring access to a structure, the substring does not have data type c; instead, it is handled like the structure itself.
Notes
For reads on substrings of character-like data objects, predefined substring functions that allow searches by specifying both substring and offset/lengths are available.
It is a good idea to specify offsets with the value 0 explicitly too (that is, dobj+0(len) instead of dobj(len)). This differentiates a substring access in the source code clearly from other language constructs that also use parentheses, such as dynamic specifications, method calls, or inline declarations.
No substring access cnt(len), sum(len) can be performed on data objects called cnt and sum unless an offset is specified explicitly. The compiler always interprets this as a number or sum of a field len in the control level processing of an extract dataset.
Obsolete syntax forms can still occur with substring access (apart from with classes).
The statement MOVE PERCENTAGE indicates an obsolete form of substring access.
