| Headings - part 4 |
| Part of the "Working With QuSheet" tutorial for QuSheet |
| Part of the "Working With QuSheet" tutorial for QuSheet |
| Summary |
The “On” column specifies the operand for the operation, as long as the operation takes an operand and a field-access operation is not being used. |
A: In the latter case if the “On” column specifies a Table, then the field specified in the field column is pulled out of the Table instead of the Table’s value. |
As QuSheet processes a Sheet, navigating down through the various Headings, it keeps values for all of the Fields that have been defined. These values are used whenever a Table is accessed – looking up the rows of the Table, in order, looking for a match between the Fields it has against the Fields present in the rows (note that if a Field is undefined in either, an automatic match for the Field takes place). |
The way QuSheet sets values for Fields comes down to two mechanisms: Selectors and Fields in non-field access Heading entries. |
Setting the selector column in a Heading or Sheet entry to a Field repeats the entry for every default value defined for that Field. If this results in Fields taking values which cause table lookups to fail then QuSheet will report an error unless the Generation Parameter to Ignore “not found” Errors when processing selections has been set. |
Setting the selector column in a Heading or Sheet entry to an actual Selector is covered in detail in the tutorial chapters on “Tables, Fields and Selectors”. |
Fields can be used as a means to pull the right row out of a table or as additional data retrieved from a Table. |
E: The example in the tutorial will now fail, however, because of an extra piece of functionality which has been added. When a field-access operation takes place in a line with an operand present, the field is first *cleared* before the operand is looked up. If the current value of the field is required then the operand should be omitted. |
Putting these two pieces of functionality together, of course, means one can use one Field to perform the lookup and another to extract the data. |
| Summary » |
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| Addenda / Errata |
A: In the latter case if the “On” column specifies a Table, then the field specified in the field column is pulled out of the Table instead of the Table’s value. |
E: The example in the tutorial will now fail, however, because of an extra piece of functionality which has been added. When a field-access operation takes place in a line with an operand present, the field is first *cleared* before the operand is looked up. If the current value of the field is required then the operand should be omitted. |
| Addenda / Errata » |
| « Summary |
The “On” column specifies the operand for the operation, as long as the operation takes an operand and a field-access operation is not being used. |
A: In the latter case if the “On” column specifies a Table, then the field specified in the field column is pulled out of the Table instead of the Table’s value. |
As QuSheet processes a Sheet, navigating down through the various Headings, it keeps values for all of the Fields that have been defined. These values are used whenever a Table is accessed – looking up the rows of the Table, in order, looking for a match between the Fields it has against the Fields present in the rows (note that if a Field is undefined in either, an automatic match for the Field takes place). |
The way QuSheet sets values for Fields comes down to two mechanisms: Selectors and Fields in non-field access Heading entries. |
Setting the selector column in a Heading or Sheet entry to a Field repeats the entry for every default value defined for that Field. If this results in Fields taking values which cause table lookups to fail then QuSheet will report an error unless the Generation Parameter to Ignore “not found” Errors when processing selections has been set. |
Setting the selector column in a Heading or Sheet entry to an actual Selector is covered in detail in the tutorial chapters on “Tables, Fields and Selectors”. |
Fields can be used as a means to pull the right row out of a table or as additional data retrieved from a Table. |
E: The example in the tutorial will now fail, however, because of an extra piece of functionality which has been added. When a field-access operation takes place in a line with an operand present, the field is first *cleared* before the operand is looked up. If the current value of the field is required then the operand should be omitted. |
Putting these two pieces of functionality together, of course, means one can use one Field to perform the lookup and another to extract the data. |
| « Addenda / Errata |
A: In the latter case if the “On” column specifies a Table, then the field specified in the field column is pulled out of the Table instead of the Table’s value. |
E: The example in the tutorial will now fail, however, because of an extra piece of functionality which has been added. When a field-access operation takes place in a line with an operand present, the field is first *cleared* before the operand is looked up. If the current value of the field is required then the operand should be omitted. |
-> output produced by QuSheet, licenced to "Richard Develyn", 15 Oct 2009 130|1|24094