In the following example, the exp function from the C library is used to calculate the exponent of a number. It expects a Float64 value as an argument, so when the value of 2 is passed to ccall, it is converted to 2.0 before being passed to the C function:

All that is good, but something seems to be missing. What about the most common use case: passing an argument to a function? Wouldn't it be called if Julia auto-converts the arguments as well? The answer may be a little surprising. Let's look at this in more detail in the following sections.