Re: diff. betw. equal and eq on simbols
Nikola Skoric <nick-news@xxxxxxxx> writes:
> Now, why would eq be more efficient than equal when comparing only
> one symbol?
Eq compares the identity of its arguments, which is typically a single
primitive CPU operation (and thus "efficient"). Equal on the other
hand does different things for different types of arguments. For
example, two lists are equal if all the elements are pairwise equal,
regardless of the identity of the lists. For symbol arguments equal
will return exactly the same result as eq, but equal must first check
what the types of the arguments are, and this type-checking is what
makes equal less efficient than eq. (That is, unless the compiler can
infer at compile-time that at least one of the arguments is a symbol,
in which case equal becomes the same as eq also in terms of
efficiency.)
--
Frode Vatvedt Fjeld
.
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