On Monday, 1 August 2022 at 12:58:27 UTC, Paul Backus wrote:
On Monday, 1 August 2022 at 11:35:25 UTC, pascal111 wrote:
I noticed that filter is using the concept of templates but
this time it's with a lambda function, not with a data type,
how can we explain this? isn't supposed to use a data type
after the exclamation mark: "auto r = chain(a, b).filter!(a =>
a > 0);"
https://dlang.org/phobos/std_algorithm_iteration.html#.filter.filter
If you look at the documentation for the filter template [1],
you will notice that the "predicate" parameter is marked with
the keyword "alias":
template filter(alias predicate)
Alias template parameters are special. They can accept not only
types, but also values, names of variables, and even things
like modules and packages as arguments. You can read more about
them in the "More Templates" chapter of Ali's book [2], and in
the official D language specification [3].
[1]
https://dlang.org/phobos/std_algorithm_iteration.html#.filter
[2]
http://ddili.org/ders/d.en/templates_more.html#ix_templates_more.alias,%20template%20parameter
[3] https://dlang.org/spec/template.html#aliasparameters
Ok! I'll read about that from the suggested sources, but with
respect to Ali's book, he should put "More Templates" after the
chapter of "templates", but he put "Pragmas" instead of that
http://ddili.org/ders/d.en/pragma.html
