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82 lines
2.4 KiB
Markdown
82 lines
2.4 KiB
Markdown
The [_INSTRREV](_INSTRREV) function searches for a substring inside another string, but unlike [INSTR](INSTR) it searches from right to left.
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## Syntax
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> position% = [_INSTRREV](_INSTRREV)([start%,] baseString$, subString$)
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## Parameter(s)
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* The optional literal or variable [INTEGER](INTEGER) start% indicates where in the baseString$ the search must start, counted from the left.
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* The baseString$ is a literal or variable [STRING](STRING) value to be searched for an exact match including [UCASE$](UCASE$).
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* The subString$ is a literal or variable [STRING](STRING) value being searched.
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## Description
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* The function returns the position% in the baseString$ where the subString$ was found, from right to left.
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* position% will be 0 if the search found no matches in the base string.
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* [_INSTRREV](_INSTRREV) returns 0 if an empty baseString$ is passed, and returns [LEN](LEN)(baseString$) with an empty subString$.
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* The start% position is useful when making multiple searches in the same string. See the example below.
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* The subString$ should be smaller or equal in [LEN](LEN) to the baseString$, or 0 is returned.
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* A start% value of 0 or less starts search from the end of the baseString$ (same as not passing a start% parameter).
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## Example(s)
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Separating a file name from a full path.
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```vb
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fullPath$ = "C:\Documents and Settings\Administrator\Desktop\qb64\internal\c\libqb\os\win\libqb_1_2_000000000000.o"
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file$ = MID$(fullPath$, _INSTRREV(fullPath$, "\") + 1)
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PRINT file$
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```
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```text
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libqb_1_2_000000000000.o
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```
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Searching for multiple instances of a substring inside a base string, going from the end to the start.
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```vb
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sentence$ = " This is a string full of spaces, including at start and end... "
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PRINT sentence$
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DO
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findPrevSpace% = _INSTRREV(findPrevSpace% - 1, sentence$, SPACE$(1))
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IF findPrevSpace% = 0 THEN
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LOCATE 4, 1
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PRINT "No more spaces"
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EXIT DO
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END IF
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LOCATE 2, findPrevSpace%
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PRINT "^"
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totalSpaces = totalSpaces + 1
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IF findPrevSpace% = 1 THEN
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LOCATE 4, 1
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PRINT "Last space found at position 1"
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EXIT DO
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END IF
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LOOP
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PRINT "Total spaces found: "; totalSpaces
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```
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```text
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This is a string full of spaces, including at start and end...
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^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^
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Last space found at position 1
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Total spaces found: 13
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```
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## See Also
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* [MID$](MID$), [INSTR](INSTR)
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* [SPACE$](SPACE$)
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