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c++vimlong-double

Split up long C++ double literal into multiple lines

I'm implementing log_10(x) in terms of log_2(x) with the following formula log_10(x) = log_2(x)/log_2(10). I want to make this function generic (eg I would like it to work with could work with Boost's cpp_bin_float_quad) and, as far as I know, there's no great way to compute log_2(10) at compile time, so I just pasted in a long literal for 1/log_2(10). The following code works but I have some issues with it:

template <typename T>
static inline T log(T x){
    T invlog2of10 = 0.301029995663981195213738894724493l;
    return invlog2of10*log2(x);
}

Issue 1: The literal is so many characters long that it makes vim slow and it breaks the syntax highlighting. Is there a standard compliant way to split this floating-point literal into multiple lines? Doing so would fix the syntax highlighting and then it'd be clearer how many digits there are in the literal. Issue 2: Is long double really the highest precision I can use for this literal? Computing this constant at compile time would be much more ideal.

I tried putting spaces, newlines, and and backslashes into the floating-point literal similar to what can be done for long string literals. This did not work.

Solution

  • Use a backslash:

    T invlog2of10 = 0.301029995663981\
195213738894724493l;

    The backslash escapes the newline.