## Writing Externals

See [pure data site](https://puredata.info/docs/faq/writingexternals), which points to [this github](https://github.com/pure-data/externals-howto) and FlextCpp

See [here](https://puredata.info/docs/faq/how-do-i-install-externals-and-help-files) for where to install externals. (On Linux it's `~/.local/lib/pd/extra/`).

## Simplest Example
helloworld.c
```c
#include "m_pd.h"

static t_class *helloworld_class;

typedef struct _helloworld {
  t_object x_obj;
} t_helloworld;

void helloworld_bang(t_helloworld *x)
{
  post("Hello world!!");
}

void *helloworld_new(void);
void helloworld_setup(void)
{
  helloworld_class = class_new(gensym("helloworld"),
    (t_newmethod)helloworld_new,
    0, sizeof(t_helloworld),
    CLASS_DEFAULT, 0);
  class_addbang(helloworld_class, helloworld_bang);
}

void *helloworld_new(void)
{
  t_helloworld *x = (t_helloworld *)pd_new(helloworld_class);
  return (void *)x;
}
```
Makefile
```
# Makefile for mylib

lib.name = helloworldlib

class.sources = helloworld.c

datafiles = 

include Makefile.pdlibbuilder
```
where Makefile.pdbuilder is [here](https://github.com/pure-data/externals-howto/blob/master/pd-lib-builder/Makefile.pdlibbuilder).