| Published By | Date | Version | Knowledge Level | Keywords |
|---|---|---|---|---|
| Sprezzatura Ltd | 01 JUN 1989 | 1.13+ | EXPERT | RTP16, XLATE |
The XLATE processor. This is actually a very useful tool for more than just standard extractions of descriptions from code files et al. The full syntax of XLATE is
XLATE(file,rec,field,action,levels.drop)
and it is the variants of field that make this function more powerful than it might at first seem. To deal with the options in turn:
| Option | Description |
|---|---|
| file | this can be a literal or a variable (but not a file variable). It can also be a dict file. |
| rec | this is the key of the record that is to be extracted from the file. It can be any valid expression and it can be multivalued. If it is multivalued all of the records specified will be read and the values returned in a multivalued array. |
| field | see "field" description below |
| action | can be X or C. X means return null if record not found, C means return the ID. Note that omitting X and C will be treated as a C. |
| levels.drop | see "levels.drop" description below |
Field can be of four types:
| Field Type | Description |
|---|---|
| Number | this just returns the field specified from the record and is the standard use for XLATE. |
| Zero | this does not return a field but rather returns the key. This is VERY useful in conjunction with the X action code. If we request a field number in place of a 0 we have no way of knowing if the record was on file or not as with an X a "" would be returned if the field was null OR if the record did not exist. With a field number of 0 we can perform a Verifile operation easily. If the record is there the id will be returned, if it is not on file a "" will be returned E.G. IF NOT(XLATE("CODES",@ANS,0,"X")) THEN CALL MSG("Code not found","","","") |
| Null ("") | this returns the entire record instead of a field. It can be used to save having to open a file for a quick one off utility program or used in conjunction with the levels.drop (q.v.) it can form a quick way of taking entire records to form a multivalued array (e.g. for stuffing a popup etc.). If we set levels.drop to 1, the record will be returned as a multivalued array and thus require no further processing to treat as a multivalue. E.G. POP.LIST=XLATE("LISTS","TEMP","","X",1) IF POP.LIST THEN WRITEV POP.LIST ON POPS,ID,4 |
| Field Name | can be used in place of field number and is more readable although slower. Has the great advantage that it can be used to extract symbolics. |
The Levels.Drop parameter tells the system how to treat delimiters found in the field/record being XLATED to. This could be useful in the above example where we extracted an entire record using a null field as it changed the field marks to value marks (and of course any value marks to sub-value marks). It is also very useful when XLATEing from a multivalued field to a multivalued field. This is best illustrated by reference to a list statement - in this example every record on the main file can store multiple parts. Every part is available in a number of colours. The symbolic Colour.Choice simply extracts the corresponding choices from the parts file. Firstly using
@ANS=XLATE("PARTS",{PNO}, "COL","X")
we get
Key.. Parts................ Colour Choice
1 P123 Red
P200 Blue
P300 Green
P400 Yellow
P563 Purple
P789 Blue
Red
Green
Lilac
Cyan
Now using
@ANS = XLATE("PARTS",{PNO},"COL" ,"X",1)
we get
Key.. Parts............ Colour Choice
1 P123 Red
Blue
P200 Green
P300 Yellow
Purple
Blue
P400 Red
P563 Green
P789 Lilac
Cyan
a much more meaningful list because the multivalues in the target have been dropped one level to sub-values and the LIST processor recognises this.
Note that under certain circumstances XLATEs can be more efficient than straightforward READs as they have their own buffers in the FRAME array.
(Volume 1, Issue 2, Pages 5-7)