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193 :: strutils.tolower

• fnco (orginal) [2013-08-02T19:58:55+02:00] view original

  a question about 'tolower'

  strutils, line 54 "result = chr(ord(c) + (ord('a') - ord('A')))"

  why not write it like below:

  "# (ord('a') - ord('A') = 32" "result = chr(ord(c) + 32)"

  when we convert a long string tolower, we can avoid call (ord('a') - ord('A')) everytime

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• Araq (orginal) [2013-08-02T20:34:15+02:00] view original

  Welcome to the world of optimizing compilers. The compiler does that for you anyway. ;-)

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• fnco (orginal) [2013-08-02T20:51:30+02:00] view original

  Hi Araq~ that's wonderful! can you explain that for me ?

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• Araq (orginal) [2013-08-02T21:34:02+02:00] view original

  This is a very simple optimization called "constant folding". It's so simple that many languages (including Nimrod) even mandate it in their specs. The compiler notices that ord('a') is always 97 independent of any runtime values and ord('A') is always 65 and then goes on and sees 97-65 is 32 and so replaces the expression (ord('a') - ord('A')) by 32 like you did.

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