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6e01fc8dce
Added new _STRCMP and _STRICMP commands for quick string comparisons. Cleaned up QB64 to finish removing the QUI (quick user insert) code and folders. Altered UCASE and LCASE routines to be faster in some situations for us.
65 lines
2.1 KiB
Plaintext
65 lines
2.1 KiB
Plaintext
The '''LEFT$''' string function returns a part of a [[STRING]] from the start a set number of places.
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{{PageSyntax}}
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:: LEFT$(stringvalue$, numberofcharacters%)
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* The string value can be any string of [[ASCII]] characters as a string variable.
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* If the number of characters exceeds the string length the entire string is returned.
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* Number of characters cannot be a negative value.
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* LEFT$ returns always starts at the first character of the string, even when a space. [[LTRIM$]] can remove leading spaces.
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''Example 1:'' Getting the left portion of a string value.
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{{CodeStart}} '' ''
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name$ = "Tom Williams"
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First$ = LEFT$(name$, 3)
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PRINT First$ '' ''
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{{CodeEnd}}
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{{OutputStart}}Tom {{OutputEnd}}
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''Example 2:'' A Replace function using LEFT$ and [[RIGHT$]] with [[INSTR]] to insert a different length word into an existing string.
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{{CodeStart}} '' ''
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text$ = "This is my sentence to change my words."
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{{Cl|PRINT}} text$
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oldword$ = "my"
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newword$ = "your"
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x = Replace(text$, oldword$, newword$)
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{{Cl|IF...THEN|IF}} x {{Cl|THEN}} {{Cl|PRINT}} text$; x
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{{Cl|END}}
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{{Cl|FUNCTION}} Replace (text$, old$, new$) 'can also be used as a {{Cl|SUB}} without the count assignment
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{{Cl|DO...LOOP|DO}}
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find = {{Cl|INSTR}}(start + 1, text$, old$) 'find location of a word in text
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{{Cl|IF...THEN|IF}} find {{Cl|THEN}}
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count = count + 1
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first$ = {{Cl|LEFT$}}(text$, find - 1) 'text before word including spaces
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last$ = {{Cl|RIGHT$}}(text$, {{Cl|LEN}}(text$) - (find + {{Cl|LEN}}(old$) - 1)) 'text after word
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text$ = first$ + new$ + last$
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{{Cl|END IF}}
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start = find
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{{Cl|LOOP}} {{Cl|WHILE}} find
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Replace = count 'function returns the number of replaced words. Comment out in SUB
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{{Cl|END FUNCTION}} '' ''
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{{CodeEnd}}
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{{OutputStart}}This is my sentence to change my words.
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This is your sentence to change your words.{{OutputEnd}}
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: ''Note:'' The [[MID$ (statement)|MID$]] statement can only substitute words or sections of the original string length. It cannot change the string length.
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''See also:''
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* [[RIGHT$]], [[MID$]]
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* [[LTRIM$]], [[RTRIM$]]
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* [[MID$ (statement)]]
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* [[INSTR]]
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{{PageNavigation}} |