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digitalmars.D.learn - Exclamation symbol "!" within functions syntax

reply pascal111 <judas.the.messiah.111 gmail.com> writes:
I noticed more than once that the exclamation "!" is used within 
functions typing, and it seems like an operator with new use, for 
example "to!int()", ".tee!(l => sum += l.length)", 
"enforce!MissingArguments...", so what dose it means?
Jul 27 2022
parent reply =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
On 7/27/22 04:00, pascal111 wrote:

 I noticed more than once that the exclamation "!" is used within 
 functions typing, and it seems like an operator with new use, for 
 example "to!int()", ".tee!(l => sum += l.length)", 
 "enforce!MissingArguments...", so what dose it means?
 


The binary ! operator is used for specifying template arguments. I have 
some explanation here:

 
http://ddili.org/ders/d.en/templates.html#ix_templates.!,%20template%20instance

Ali
Jul 27 2022
next sibling parent pascal111 <judas.the.messiah.111 gmail.com> writes:
On Wednesday, 27 July 2022 at 11:09:19 UTC, Ali Çehreli wrote:

 On 7/27/22 04:00, pascal111 wrote:

 I noticed more than once that the exclamation "!" is used 
 within functions typing, and it seems like an operator with 
 new use, for example "to!int()", ".tee!(l => sum += 
 l.length)", "enforce!MissingArguments...", so what dose it 
 means?
 


 The binary ! operator is used for specifying template 
 arguments. I have some explanation here:


 http://ddili.org/ders/d.en/templates.html#ix_templates.!,%20template%20instance

 Ali


I think I got it now, it's easy, I thought it so advanced D 
feature.
Jul 27 2022
prev sibling parent reply pascal111 <judas.the.messiah.111 gmail.com> writes:
On Wednesday, 27 July 2022 at 11:09:19 UTC, Ali Çehreli wrote:

 On 7/27/22 04:00, pascal111 wrote:

 I noticed more than once that the exclamation "!" is used 
 within functions typing, and it seems like an operator with 
 new use, for example "to!int()", ".tee!(l => sum += 
 l.length)", "enforce!MissingArguments...", so what dose it 
 means?
 


 The binary ! operator is used for specifying template 
 arguments. I have some explanation here:


 http://ddili.org/ders/d.en/templates.html#ix_templates.!,%20template%20instance

 Ali


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
Aug 01 2022
parent reply Paul Backus <snarwin gmail.com> writes:
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
Aug 01 2022
parent pascal111 <judas.the.messiah.111 gmail.com> writes:
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
Aug 01 2022