`locate f` -- for a symbol interpreted function

`f` returns a sequence

`(n,i,c,j,d,k,e)` describing the location of the definition in the source code. The name of the source file is

`n` and the code is occupies line

`i` column

`c` through line

`j` column

`d`, with the central point of interest located at line

`k` column

`e`. If the function

`f` is compiled, then the location is not available, and

null is returned.

If `f` is a sequence, then lookup is applied first, and then the location of the resulting function is provided.

If `f` is null, then null is returned.