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NullRecords

Status: Experimental

present and registered, but lightly documented and not yet covered by dedicated tests.

Description

NullRecords

is an option for Read and ReadList specifying whether a null record is assumed between two adjacent record separators. The default is False.

Examples (2)

Every input below was run against the current Mathilda build and its output recorded.

Applications (2)

Default: empty field dropped

In[1]:= s = OpenWrite["/tmp/mathilda_null.txt"]; WriteString[s, "a,b,,c"]; Close[s]; ReadList["/tmp/mathilda_null.txt", Record, RecordSeparators -> {","}]
Out[1]= {"a", "b", "c"}

Empty field kept

In[2]:= s = OpenWrite["/tmp/mathilda_null.txt"]; WriteString[s, "a,b,,c"]; Close[s]; ReadList["/tmp/mathilda_null.txt", Record, RecordSeparators -> {","}, NullRecords -> True]
Out[2]= {"a", "b", "", "c"}

Implementation notes

Definition. NullRecords is an option for Read and ReadList specifying whether a null (empty) record is assumed between two adjacent record separators. It has no builtin and no value of its own ā€” an inert, Protected keyword carried in the reader's option list, with default False.

Representation. A bare EXPR_SYMBOL (interned SYM_NullRecords). Both read.c and readlist.c seed their default option set with rule_of(SYM_NullRecords, False). When True, the Record reader keeps the empty field that lies between two consecutive RecordSeparators, so "a,b,,c" split on "," yields {"a", "b", "", "c"} rather than {"a", "b", "c"}.

Usage & limits. Protected; meaningful only as a Read/ReadList option in combination with the Record read type and RecordSeparators. It has a registered default, so SetOptions on it works. The word-level analogue is NullWords.

Attributes: none registered.

References

Notes & additional examples

Notes

NullRecords is an option for Read and ReadList specifying whether a null (empty) record is assumed between two adjacent record separators. The default is False.

With the default, "a,b,,c" split on "," collapses the doubled separator and yields {"a", "b", "c"}; with NullRecords -> True the empty field between the two commas is kept, giving {"a", "b", "", "c"}. It is an inert, Protected keyword with a registered default (so SetOptions works), meaningful only with the Record read type and RecordSeparators. The word-level analogue is NullWords.