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William D Clinger wrote:
> Out of curiosity, what string representations does SRFI-75 penalize > which you consider to be poor? Suppose each string s is represented by a vector of 2^21 elements, where element i consists of a list of numbers, in IEEE double precision, that represent the indexes within s at which the character c appears, where c is the Unicode scalar value f(i), where f is represented by a global association list that maps scalar values to indexes (i.e. f-inverse). SRFI-75 allows that representation, yet penalizes it. I also consider it to be a poor representation.
You consider this a poor representation because it does not allow constant-time random access or because it does not allow linear-time traversal? Or simply because of the space cost?
Consider an implementation that internally represents strings as if they were doubly-linked lists and cached the position of the last index. This allows linear-time traversal but not constant-time random access. Would you consider this a poor implementation?
The thing is, SRFI-75 does not mention how one accesses the characters in a string, so I presume that R5RS character indices will remain the only portable way to do this.
Regards, Alan -- Dr Alan Watson Centro de Radioastronomía y Astrofísica Universidad Astronómico Nacional de México