JCL Help:TJclTabSet
JCL Help: TJclTabSet Class
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TJclTabSet
Summary
Represents a tab set that can be used to expand tabs to spaces, or vice versa.
Pascal
public TJclTabSet = class(TInterfacedObject, IToString);
Description
The TJclTabSet class represents tabulation information. Each instance can specify:
- Whether the column positions are zero-based
- Individual tabulation positions
- Tabulation width for columns beyond those specified by the individual tabulation positions.
The class then provides functionality to:
- Determine the next tabulation position from a given starting column
- Determine the optimal tab and space characters needed to get from one column to another
- Expand tab characters into a sequence of spaces, optionally starting at an arbitrary column
- Collapse a sequence of space and tab characters into an optimized sequence of tab and space characters, optionally starting at an arbitrary column
The class contains logic to allow automatic tab width determination by setting the tabulation width to zero or a negative value; in this case the tab width is determined by the provided tabulation positions in the following manner:
| Situation | ActualTabWidth |
| No tabulation positions defined | 2 |
| One tabulation position defined | the defined tabulation position |
| Two or more tabulation positions defined | the distance between the last two tabulation positions |
nil - safetyThe public methods and properties that do not modify the tab set are nil-safe, meaning they will work when used on a nil reference. A nil tab set will behave as if explicitly set to:
- assume zero-based column positions
- no defined tabulation positions
- a tabulation width of 2
Note that reading any of the public properties on a nil instance will work properly.
Examples
// initiate a tab set with (zero-based) stops at 15, 20 and 30, and a tab width of 2 forThe above snippet will result in x containing the string (· represents a space character):
// tabs beyond the column 30
tabs := TJclTabSet.Create([15, 20, 30], True, 2);
try
x := tabs.Expand('MyLabel:'#9'LD'#9'A,(HL)'#9'; Initialize A register');
finally
tabs.Free;
end;MyLabel:·······LD···A,(HL)····;·Initialize·A·register. In this case the first tab character (ASCII code 9) was transformed into seven spaces, the second tab character into three spaces and the third tab character into four spaces.
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Unit
Donator
Marcel Bestebroer
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