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Note that this uses not only trigraphs but also digraphs (here `<%`, `%>` and `%:`), which are similar to trigraphs in intended usages but behave much different

Note that this uses not only trigraphs but also digraphs (here `<%`, `%>` and `%:`), which are similar to trigraphs in intended usages but behave much differently to digraphs in that it is a proper token and not a preprocessor substitution pattern. `printf("??(foo??)<:bar:>%c", "quux"<:1:>)` prints `[foo]<:bar:>u`, for example. Therefore digraphs are deemed less dangerous (however obscure) than trigraphs and do not require any compiler options.

DonHopkins 4y ago
Bjarne Stroustrup proposed Generalized Overloading for C++2000, which not only lets you override all kinds of white space, like between two symbols separated left to right by a space (i.e. "a b" to add a to b), or two symbols separated top to bottom by a newline (i.e. "a \n b" to divide a by b, like a fraction), or even by tabs, or either kind of comment, but it also lets you override writing two symbols next to each other without any separation (i.e. "ab" to multiply a by b, which mathematicians love)! Of course they also had to limit the number of characters per symbol to 1 in order to unambiguously support the "ab" syntax for multiplying a and b (or however you wanted to overload the "absence of white space" operator), but fortunately they mitigated that little problem by making C++ fully supports Unicode, so you had thousands of single character Unicode variable names to choose from. His prophetic intuition was spot-on, now that there are so many expressive and inclusive Emoji characters to use for single character variable names! https://www.stroustrup.com/whitespace98.pdf https://www.stroustrup.com/whitespace98.pdf I really appreciate Bjarne Stroustrup's clean simple design and coherent long term vision for C++2000, and I'm looking forward to using three dimensional white space overloading in C++3D.
- ralphb 4y ago
  I am almost unhappy to learn that this was a joke. Would have been nice to put a final (personal) nail in the C++ coffin with this insanity. However, I guess it says enough that I did have to dig quite far into the paper to realize whether Bjarne was joking or not.
- gpderetta 4y ago
  We do not have yet three dimensional white space overloading unfortunately, will have to wait for the next release train, targeting C++26. In the meantime, you can use multidimensional analog literals: http://www.eelis.net/C++/analogliterals.xhtml http://www.eelis.net/C++/analogliterals.xhtml

DonHopkins 4y ago

Bjarne Stroustrup proposed Generalized Overloading for C++2000, which not only lets you override all kinds of white space, like between two symbols separated left to right by a space (i.e. "a b" to add a to b), or two symbols separated top to bottom by a newline (i.e. "a \n b" to divide a by b, like a fraction), or even by tabs, or either kind of comment, but it also lets you override writing two symbols next to each other without any separation (i.e. "ab" to multiply a by b, which mathematicians love)! Of course they also had to limit the number of characters per symbol to 1 in order to unambiguously support the "ab" syntax for multiplying a and b (or however you wanted to overload the "absence of white space" operator), but fortunately they mitigated that little problem by making C++ fully supports Unicode, so you had thousands of single character Unicode variable names to choose from. His prophetic intuition was spot-on, now that there are so many expressive and inclusive Emoji characters to use for single character variable names! https://www.stroustrup.com/whitespace98.pdf https://www.stroustrup.com/whitespace98.pdf I really appreciate Bjarne Stroustrup's clean simple design and coherent long term vision for C++2000, and I'm looking forward to using three dimensional white space overloading in C++3D.

ralphb 4y ago
I am almost unhappy to learn that this was a joke. Would have been nice to put a final (personal) nail in the C++ coffin with this insanity. However, I guess it says enough that I did have to dig quite far into the paper to realize whether Bjarne was joking or not.
gpderetta 4y ago
We do not have yet three dimensional white space overloading unfortunately, will have to wait for the next release train, targeting C++26. In the meantime, you can use multidimensional analog literals: http://www.eelis.net/C++/analogliterals.xhtml http://www.eelis.net/C++/analogliterals.xhtml