The user filter examples are listed below.
1 – uf_example1
The following example assumes that the disks are named
UDISK{n} where {n} is a number, for example UDISK1,
UDISK13. This filter replaces such disk names with the
string "DISK_NAME":
global_replace ( 'UDISK' + number, 'DISK_NAME')
The pattern to replace is built from a string literal
('UDISK'), the concatenation operator (+) and the
pattern "number" included in the supplied definitions
file. The pattern "number" matches a sequence of
digits.
The replacement string is the string literal 'DISK_
NAME'.
2 – uf_example2
This example uses the supplied "null" pattern with
the DECTPU alternation operator to include an optional
element in a pattern.
Supposing that, in the previous example, some of the
disk names do not include the leading "U", for example
DISK7. The following filter replaces disk names with or
without the leading "U":
global_replace ( ("U"|null) + "DISK" + number,
"DISK_NAME")
3 – uf_example3
The following example filters dates in the form DD-MMM-
YYYY, for example 11-OCT-1999. Because it only filters
this one form of date, it is quicker than the built-in
date filter which filters many different date formats.
It is also not the exact equivalent of the built-in
date filter in other respects, for example it treats
37-NOV-0999 as a date, but should be sufficient for
most purposes.
day := any(" 123") + digit;
month := "JAN" | "FEB" | "MAR" | "APR" |
"MAY" | "JUN" | "JUL" | "AUG" |
"SEP" | "OCT" | "NOV" | "DEC";
year := any(digits,4);
date := day + "-" + month + "-" + year;
global_replace( date, "dd-mmm-yyyy");
This filter defines the pattern variables "day",
"month" and "year" which are then used to define the
pattern variable "date" used in the call to global_
replace.
The "day" pattern uses the DECTPU function "any" to
match either a space or one of the characters "1", "2"
or "3", followed by a digit.
The "month" pattern uses the DECTPU pattern alternation
operator "|" to specify a list of alternative string
literals.
The "year" pattern uses the DECTPU function "any"
with the supplied pattern "digits". The "4" parameter
indicates that exactly 4 digits are to be matched.
The "date" pattern concatenates these patterns and
linking punctuation.
4 – uf_example4
This filter removes blank lines using the DECTPU
keywords LINE_BEGIN and LINE_END.
global_replace( LINE_BEGIN + LINE_END, '');
The LINE_END keyword absorbs the new line.
The above filter only replaces lines containing no
characters. The following filter also replaces lines
containing only spaces and tab characters:
global_replace( LINE_BEGIN + (white_space|null) +
LINE_END, '');
5 – uf_example5
This example demonstrates how to use surrounding
text to identify a string to be replaced without also
replacing the surrounding text.
The following filter replaces the month part of
a date with the string "mmm". For example, the
string "14-OCT-1999" will be replaced by the string
"14-mmm-1999":
day := any(" 123") + digit;
month := "JAN" | "FEB" | "MAR" | "APR" |
"MAY" | "JUN" | "JUL" | "AUG" |
"SEP" | "OCT" | "NOV" | "DEC";
year := any(digits,4);
date := (day + "-"@day_part) + month + ("-" + year@year_part);
global_replace( date, 'str(day_part) + "mmm" + str(year_part)',,ON);
The day part of the date and the "-" character are
assigned to the partial pattern variable day_part and
the year part of the date and preceding "-" assigned
to year_part. These partial pattern variables are then
included in the replacement string.
When partial pattern variable are used in the
replacement string they must be evaluated for
each replacement. To do this, set the parameter
evaluate_replacement to ON, as shown above.
When the replacement string is to be evaluated, string
literals must be nested inside further quotes. This
is most easily done by using single quotes for the
outer string and double quotes for any nested string
literals, or vice-versa. Also, any partial pattern
variables must be converted to strings using the DECTPU
procedure STR.
Note that including LINE_END in the definition of a
partial pattern variable does not have the effect
of retaining the line break. See example 6 for a
resolution of this problem.
6 – uf_example6
If the search pattern contains LINE_END, the matched
line break will be removed, causing the next line to
be appended to the current line. To use LINE_END to
only provide context for the search, the line break
must be reinserted. This is done using the parameter
convert_linefeeds.
If the convert_linefeeds parameter is specified as ON,
any linefeed characters appearing in the replacement
string are removed and the built-in DECTPU procedure
SPLIT_LINE is called at the point of the linefeed
character.
The following filter replaces any numbers that are the
last characters on a line with the string "x":
global_replace (number+LINE_END, "x"+lf,,,ON)
The "lf" pattern is defined as a linefeed character in
the supplied definitions file.
If a LINE_END is included in a partial pattern
variable, the line break can be retained by specifying
the second optional parameter to the DECTPU STR
procedure as a linefeed character, for example:
global_replace (number+(LINE_END@sep),
'"x"+STR(sep,lf)',,ON,ON)
The second parameter to STR specifies the string that
line breaks occurring in the first parameter should be
converted to. Line breaks are retained by specifying
the linefeed character and setting the parameter
convert_linefeeds to ON.
7 – uf_example7
The DECTPU keyword UNANCHOR can be used to replace
sections of text delimited by specified strings. The
following replaces all text between the strings "/*"
and "*/" with the string "/* Text deleted */". The text
may run across line boundaries:
global_replace ( "/*" + UNANCHOR + "*/",
"/* Text deleted */")
Note that while a similar effect is possible using the
COMPARE/SENTINEL command, the filter can be applied
to individual tests, whereas the /SENTINEL qualifier
applies only to collections.
8 – uf_example8
The global_replace procedure can be used for many
filtering tasks. However any DECTPU commands can be
used to build filters. The file being filtered is read
into the buffer "filter_buffer" before the user filters
are applied and written out afterwards.
The following filter uses the DECTPU EDIT procedure to
convert all characters to upper case:
EDIT( filter_buffer, UPPER, OFF)
Note that while a similar effect is possible using the
COMPARE/IGNORE=CASE command, the filter can be applied
to individual tests, whereas the IGNORE qualifier
applies only to collections.
The following filter searches for numbers and replaces
them only if they are in a specified range:
POSITION (BEGINNING_OF (filter_buffer));
LOOP
found_range := SEARCH_QUIETLY (number, FORWARD);
EXITIF found_range = 0;
POSITION (END_OF(found_range));
MOVE_HORIZONTAL(1);
value := INT(STR(found_range));
IF (value>350) AND (value<570)
THEN
COPY_TEXT ("XXX");
ERASE (found_range);
ENDIF;
ENDLOOP;
The initial POSITION is required to ensure that the
whole of the filter_buffer is processed, because the
editing point is undefined at the start of each filter.
Then, as each number is processed, the editing point is
moved to the end of the number. The MOVE_HORIZONTAL
procedure call is necessary because the previous
POSITION leaves the editing point at the last character
of the number, which would result in an immediate match
on the next call to SEARCH_QUIETLY.