问题
I am taking a class in C++ and I noticed there are only a few math operators to use. I also noticed that C++ does not come with an exponential operator within its math library.
Why must one always write a function for this? Is there a reason for the makers of C++ to omit this operator?
回答1:
You don't write a function for this (unless you're insane, of course). There's a perfectly good pow function defined in the <cmath> header.
Aside: if you try to use
^as a power operator, as some people are wont to do, you'll be in for a nasty surprise. It's the exclusive-or (XOR) operator (see here).
回答2:
Most C operations readily intended to mapped to a single processor instruction when C was invented. At the time, exponentiation was not a machine instruction, thus the library routine.
回答3:
According to Bjarne Stroustrup in his book The design and evolution of C++. They decided to avoid exponential operator because :
- An operator provides notational convenience, but does not provide any new functionality. Members of the working group, representing heavy users of scientific/engineering computation, indicated that the operator syntax provides minor syntactic convenience.
- Every user of C++ must learn this new feature
- Users have stressed the importance of susbtituting their own specialized exponentiation functions for the system default, which would not be possible with an intrinsic operator
- The proposal is not sufficiently well motivated. In particular, by looking at one 30000 line Fortran program one cannot conclude that the operator would be widely used in C++
- The proposal requires adding a new operator and adding another precedence level thus increasing the complexity of the language
回答4:
What platform and which compiler are you using? My guess is TurboC. Mostly cmath file has most of the mathematical functions covered in other compilers.
来源：https://stackoverflow.com/questions/3775274/exponential-operator-in-c