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Ranging over Strings and Rune Slices: Differences and Similarities
Question
When iterating over a string using for range and a rune slice ([]rune(str)), one might expect similar results. However, there exists a subtle difference between the two approaches. Can you identify it and explain why it occurs?
Answer
While both for range loops over strings and rune slices yield the same result for basic characters (e.g., ASCII), a difference arises when dealing with multibyte characters.
String Indexing
Strings are essentially sequences of bytes. Indexing a string is appropriate for manipulating bytes or when dealing with single-byte characters. However, indexing can be problematic when working with multibyte characters.
Range Loops on Strings
The for range loop over strings behaves uniquely. It combines the characteristics of both byte and rune slices.
This special behavior of for range loops over strings means that the index i can increment by more than one during iterations, especially when the string contains multibyte characters.
Conclusion
When working with multibyte characters, the choice between ranging over the string or its rune slice depends on the desired behavior. For manipulating bytes, indexing a string is suitable. For working with characters or code points, using []rune(str) and ranging over it provides clearer and more intuitive results.
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