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README.md
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@ -74,7 +74,7 @@ Bill (Heath) Gates 65 3.3
# Single header
The library can be used with a single header file **`ssp.hpp`**, but it suffers a slight performance loss when converting floating point values since the **`fast_float`** library is not present within the file.
The library can be used with a single header file **`ssp.hpp`**, but it suffers a significant performance loss when converting floating point values since the **`fast_float`** library is not present within the file.
# Installation
@ -92,7 +92,7 @@ The library supports [CMake](#Cmake) and [meson](#Meson) build systems
## Headers
The parser can be told to use only certain columns by parsing the header. This can be done by using the **`use_fields`** method. It accepts any number of string-like arguments or even an **`std::vector<std::string>`** with the field names. If any of the fields are not found within the header or if any fields are defined multiple times it will result in an error.
The parser can be told to use only certain columns by parsing the header. This can be done with the **`use_fields`** method. It accepts any number of string-like arguments or even an **`std::vector<std::string>`** with the field names. If any of the fields are not found within the header or if any fields are defined multiple times it will result in an error.
```shell
$ cat students_with_header.csv
Id,Age,Grade
@ -116,7 +116,7 @@ James Bailey 2.5
Brian S. Wolfe 1.9
Bill (Heath) Gates 3.3
```
The header can be ignored using the **`ss::ignore_header`** [setup](#Setup) option or by calling the **`ignore_next`** method after the parser has been constructed.
The header can be ignored using the **`ss::ignore_header`** [setup](#Setup) option or by calling the **`ignore_next`** method after the parser has been constructed. If the header has been ignored calling any method related to header usage will result in a compilation error.
```cpp
ss::parser<ss::ignore_header> p{file_name};
```
@ -124,10 +124,10 @@ The fields with which the parser works with can be modified at any given time. T
```cpp
// ...
ss::parser<ss::throw_on_error> p{"students_with_header.csv"};
p.use_fields("Id", "Grade");
p.use_fields("Grade");
const auto& [id, grade] = p.get_next<std::string, float>();
std::cout << id << ' ' << grade << std::endl;
const auto& grade = p.get_next<std::string>();
std::cout << grade << std::endl;
if (p.field_exists("Id")) {
p.use_fields("Grade", "Id");
@ -139,10 +139,32 @@ The fields with which the parser works with can be modified at any given time. T
```
```shell
$ ./a.out
James Bailey 2.5
40 Brian S. Wolfe
65 Bill (Heath) Gates
2.5
1.9 Brian S. Wolfe
3.3 Bill (Heath) Gates
```
The header is parsed with the same rules as other rows, the only difference is that **`multiline`** will be disabled when parsing the header. To get the data that is
present in the header as a **`std::vector<std::string>`**, the **`header`** method can be used, and to get the header line before it has been parsed, the **`raw_header`** method can be used:
```cpp
// ...
ss::parser<ss::throw_on_error> p{"students_with_header.csv"};
std::cout << p.raw_header() << std::endl;
for (const auto& field: p.header()) {
std::cout << "> " << field << std::endl;
}
// ...
```
```shell
$ ./a.out
Id,Age,Grade
> Id
> Age
> Grade
```
Methods related to headers can also fail, the error handling of these is done in the same way as for other methods.
## Conversions
An alternate loop to the example above would look like:
```cpp