HP OpenVMS Systems Documentation
The REPLACING phrase names a search argument of one or more characters and a condition under which the string can be applied to the item being inspected. Associated with the search argument is the replacement value, which must be the same length as the search argument. Each time the search argument finds a match in the item being inspected, under the condition stated, the replacement value replaces the matched characters.
A BEFORE/AFTER phrase can be used to delimit the area of the item being
inspected. A search argument applies only to the delimited area of the
184.108.40.206 The Search Argument
The CHARACTERS form of the search argument specifies that every character in the delimited string being inspected should be considered to match an imaginary character that serves as the search argument. Thus, the replacement value replaces each character in the delimited string. For example:
INSPECT ITEMA REPLACING CHARACTERS ...
The ALL, LEADING, and FIRST forms of the search argument specify a particular character string, which can be represented by a literal or an identifier. The search argument character string can be any length. However, each character of the argument must match a character in the delimited string before the compiler considers the argument matched. For example:
INSPECT ITEMA REPLACING ALL ...
The necessary literal and identifier characteristics are as follows:
The words ALL, LEADING, and FIRST supply conditions that further delimit the inspection operation:
Whenever the search argument finds a match in the item being inspected, the matched characters are replaced by the replacement value. The word BY followed by an identifier or literal specifies the replacement value. For example:
INSPECT ITEMA REPLACING ALL "A" BY "X" ALL "D" BY "X".
The replacement value must always be the same size as its associated search argument.
If the replacement value is a literal character-string, it must be either a nonnumeric literal or a figurative constant (other than ALL literal). A figurative constant represents as many characters as the length of the search argument requires.
If the replacement value is an identifier, it must be an elementary
item of DISPLAY usage. It can be any class. However, if it is not
alphanumeric, the compiler conducts an implicit redefinition of the
item. This redefinition is the same as the BEFORE/AFTER redefinition
discussed in Section 5.3.2.
220.127.116.11 The Replacement Argument
The replacement argument consists of the search argument (with its condition and character-string), the replacement value, and an optional BEFORE/AFTER phrase, as shown in Figure 5-5.
Figure 5-5 The Replacement Argument
One INSPECT...REPLACING statement can contain more than one replacement argument. Several replacement arguments form an argument list, and the manner in which the list is processed affects the action of any given replacement argument.
The following examples show INSPECT statements with replacement argument lists. The text following each one tells how that list will be processed.
INSPECT FIELD1 REPLACING ALL "," BY SPACE ALL "." BY SPACE ALL ";" BY SPACE.
The previous three replacement arguments all have the same replacement value, SPACE, and are active over the entire item being inspected. The statement replaces all commas, periods, and semicolons with space characters and leaves all other characters unchanged.
INSPECT FIELD1 REPLACING ALL "0" BY "1" ALL "1" BY "0".
Each of these two replacement arguments has its own replacement value and is active over the entire item being inspected. The statement exchanges zeros for 1s and 1s for zeros. It leaves all other characters unchanged.
INSPECT FIELD1 REPLACING ALL "0" BY "1" BEFORE SPACE ALL "1" BY "0" BEFORE SPACE.
When a search argument finds a match in the item being inspected, the code replaces that character-string and scans to the next position beyond the replaced characters. It ignores the remaining arguments and applies the first argument in the list to the character-string in the new position. Thus, it never inspects the new value that was supplied by the replacement operation. Because of this, the search arguments can have the same values as the replacement arguments with no chance of interference.
The statement also exchanges zeros and 1s. Here, however, the first space in FIELD1 causes both arguments to become inactive.
INSPECT FIELD1 REPLACING ALL "0" BY "1" BEFORE SPACE ALL "1" BY "0" BEFORE SPACE CHARACTERS BY "*" BEFORE SPACE.
The first space causes the three replacement arguments to become
inactive. This argument list exchanges zeros for 1s, 1s for zeros, and
asterisks for all other characters in the delimited area. If the BEFORE
phrase is removed from the third argument, that argument will remain
active across all of FIELD1. Within the area delimited by the first
space character, the third argument replaces all characters except 1s
and zeros with asterisks. Beyond this area, it replaces all characters
(including the space that delimited FIELD1 for the first two arguments,
and any zeros and 1s) with asterisks.
18.104.22.168 Interference in Replacement Argument Lists
When several search arguments, all active at the same time, contain one or more identical characters, they can interfere with each other---and consequently affect the replacement operation. This interference is similar to the interference that occurs between tally arguments.
The action of a search argument is never affected by the BEFORE/AFTER delimiters of other arguments, because the compiler scans for delimiter matches before it scans for replacement operations.
The action of a search argument is never affected by the characters of any replacement value, because the scanner does not inspect the replaced characters again during execution of the INSPECT statement. Interference between search arguments, therefore, depends on the order of the arguments, the values of the arguments, and the active/inactive status of the arguments. The discussion in Section 22.214.171.124 about interference in tally argument lists generally applies to replacement arguments as well.
The following rules help minimize interference in replacement argument lists: