[R] Unobtainable source code of specific functions

[juiie@@i@croix m@iii@g oii stude@t@uiiege@be]

Dear all,

I currently work on a translation of a cost surface function from R to Python for my dissertation at university. In this context, I have to understand the "AccCost" method (https://rdrr.io/cran/gdistance/src/R/accCost.R). This method calls the function "shortest.paths" among other functions. This is precisely the function that computes the cost surface so I found the source code with "getAnywhere(shortest.paths())", but my problem is that this code calls other functions that cannot be accessed with getAnywhere or on the web... These functions are "C_R_igraph_finalizer", "C_R_igraph_get_graph_id" and "C_R_igraph_shortest_paths". My question is therefore the following, how or where could I find these source code ? (Note : I have the package Igraph installed)

Thanks a lot for the help,

Julien Lacroix