Bug: example of concatenation by expression templates not working

[orefkov]

Describe the bug

I tried to reproduce that example from the documentation, but it didn't compile.

auto email = sz::concatenate(name, "@", domain, ".", tld);   // 0 allocations
auto email = name | "@" | domain | "." | tld;                // 0 allocations
sz::string email = name | "@" | domain | "." | tld;          // 1 allocations

Steps to reproduce

That source not compiled.

#include <stringzilla/stringzilla.hpp>
namespace sz = ashvardanian::stringzilla;
void stringzilla_concat(sz::string_view name, sz::string_view domain, sz::string_view tld) {
    auto email = sz::concatenate(name, "@", domain, ".", tld);
    sz::string result = email;
}

Error:

error: type 'ashvardanian::stringzilla::basic_string_slice<const char> &' cannot be used prior to '::' because it has no members
|     using value_type = typename first_type_::value_type;

Need std::remove_cvref_t<first_type_>::value_type;.

That sources not comiled too

void stringzilla_concat(sz::string_view name, sz::string_view domain, sz::string_view tld) {
    auto email = name | "@" | domain | "." | tld;
    sz::string result = email;
}

Error:

error: invalid operands to binary expression ('sz::string_view' (aka 'basic_string_slice<const char>') and 'const char[2]')
|     auto email = name | "@" | domain | "." | tld;

And that

void stringzilla_concat(sz::string name, sz::string_view domain, sz::string_view tld) {
    auto email = name | "@" | domain | "." | tld;
    sz::string result = email;
}

Error:

error: no viable conversion from 'concatenation<concatenation<concatenation<concatenation<basic_string_slice<const char>, 
basic_string_slice<const char>>, basic_string_slice<const char> &>, const char (&)[2]>, basic_string_slice<const char> &>'
to 'sz::string' (aka 'basic_string<char, std::allocator<char>>')

And that

void stringzilla_concat(sz::string name, sz::string_view domain, sz::string_view tld) {
    auto email = name | "@" | domain | "." | tld;
    sz::string result{email};
}

Error

error: member reference base type 'const char[2]' is not a structure or union
|     std::size_t size() const noexcept { return first.size() + second.size(); }

Expected behavior

Can compiled only that:

void stringzilla_concat(sz::string name, sz::string_view domain, sz::string_view tld) {
    auto email = name | sz::string_view{"@"} | domain | sz::string_view{"."} | tld;
    sz::string result{email};
}

or

void stringzilla_concat(sz::string_view name, sz::string_view domain, sz::string_view tld) {
    auto email = sz::concatenate(sz::string_view{name}, sz::string_view{"@"}, sz::string_view{domain}, sz::string_view{"."}, sz::string_view{tld});
    sz::string result{email};
}

StringZilla version

v4.6

Operating System

Windows 10, Clang19, C++20. Ubuntu 22.4, GCC-13

Hardware architecture

x86

Which interface are you using?

C++ bindings

Contact Details

orefkov@gmail.com

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• I am open to being mentioned in the project .git history as a contributor

Is there an existing issue for this?

• I have searched the existing issues

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• I agree to follow this project's Code of Conduct