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41 lines
2.1 KiB
Plaintext
41 lines
2.1 KiB
Plaintext
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The '''INSTR''' function searches for the first occurance of a search [[STRING]] within a string and returns the position it was found.
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{{PageSyntax}}
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:: position% = INSTR([start%,] basestring$, searchstring$)
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* The basestring position of the first character of the searchstring is returned by the function if found.
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* Position returned will be 0 if the search found no matches in the base string.
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* Start [[INTEGER]] position is optional. Must be at least 1 (start of a string) when used or an [[ERROR Codes|Illegal function call]] will occur.
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* The Start position is useful when making multiple searches in the same string. Otherwise it starts at the beginning again!
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* Base string and search string are any literal or variable [[STRING]] values.
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* The search string should be smaller than the base string!
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* Non-zero position return values can be used as a new start position by adding 1 to re-search the base string.
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* In a loop, INSTR can search an entire file for occurences of certain words. See the [[MID$ (statement)|MID$]] statement example.
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''Example:'' Reading more than one instance of a word in a string using the INSTR return value as the start value plus 1.
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{{CodeStart}} '' ''
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text$ = "The cats and dogs where playing, even though dogs don't like cats."
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{{Cl|DO...LOOP|DO}}
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findcats% = {{Cl|INSTR}}(findcats% + 1, text$, "cats") ' find another occurance after
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{{Cl|IF...THEN|IF}} findcats% {{Cl|THEN}} {{Cl|PRINT}} "There is 'cats' in the string at position:"; findcats%
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{{Cl|LOOP}} {{Cl|UNTIL}} findcats% = 0
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findmonkey% = {{Cl|INSTR}}(text$, "monkeys") ' find any occurance?
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PRINT findmonkey%; "'monkeys' were found so it returned:"; findmonkey% '' ''
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{{CodeEnd}}
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{{OutputStart}}There is 'cats' in the string at position: 5
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There is 'cats' in the string at position: 62
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0 'monkeys' were found so INSTR returned: 0
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{{OutputEnd}}
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: ''Explanation:'' When the INSTR return value is 0 there are no more instances of a string in a string so the search loop is exited.
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''See also:''
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* [[MID$]], [[MID$ (statement)]]
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* [[LEFT$]], [[RIGHT$]]
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{{PageNavigation}}
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