c - glib how address to index g_ptr_array -

i have 3 structures , use gnome glib library have dynamic array.

typedef struct neuron {     //number of inputs neuron     int numinputs;       //growing array of weights each input     garray* arrweight;  }neuron;  typedef struct neuronlayer {     //number of neurons in layer     int numneurons;     //growing array of neurons      gptrarray* arrneurons; }layer;  typedef struct net {     int numinputs;     int numoutputs;     int numhiddenlayers;     int neuronsperhiddenlayer;     //each layer of neurons      gptrarray* arrlayers; }net; 

i want write cycle

for (k = 0; k < net->arrlayers->pdata[i].arrneuron->pdata[j].numinputs; k++) 

but dont know how address array. compiler (clang say) :

member reference base type 'gpointer' (aka 'void *') not structure or union.

structure of gptrarray:

 struct gptrarray   {        gpointer *pdata;        guint    len;   }; 

i think should write

net->arrlayers->pdata[i*sizeof(layer)].arrneurons->pdata[j*sizeof(neuron)].numinputs 

gpointer generic pointer. using store pointer of specific type. access elements must use type cast.

i first try break statement down. looks this:

net->arrlayers->pdata[i].arrneuron->pdata[j].numinputs 

i assume net variable of type net *.

net->arrlayers of type gptrarray *.

net->arrlayers->pdata of type gpointer *, i.e. void **, pointer pointer.

net->arrlayers->pdata[i] of type gpointer, i.e. void *, pointer.

now want access element. judging context, want interpret pointer pointer layer. however, compiler doesn't know that. need tell compiler.

so should add cast, (layer *)net->arrlayers->pdata[i].

now since of type layer * , not layer, still need -> instead of . access element, should become:

((layer *)net->arrlayers->pdata[i])->arrneuron 

now need access pdata again. same above, i'll skip explanation , show correct method:

((neuron *)((layer *)net->arrlayers->pdata[i])->arrneuron->pdata[j])->numinputs 

as can see messy. better split several statements enhance readability, , doing may skip casts:

int current_num_inputs(net * net, size_t i, size_t j) {     layer *current_layer = net->arrlayers->pdata[i];     neuron *current_neuron = current_layer->arrneuron->pdata[j];     return current_neuron->numinputs; } 

then in for loop:

for(k = 0; k < current_num_inputs(net, i, j); k++) { // ...