Scoping rules for variable and functions in contained subroutines

Question

I have a problem understanding why a variable (i) declared in a subroutine is seen in a contained subroutine, but that this is not true for a function (fi

Answer 1

The simplest fix is to use

double precision, external :: fie

the external attribute (also can be specified by the external statement) says: this is a procedure, I am not declaring a local variable.

For the declaration without the external to be interpreted as a function declaration the function reference must be present within the function body. Internal functions don't count. And therefore the compiler created a local double precision variable called fie.

Thank's to IanH for the relevant standard rule (from Fortran 2008 (16.5.1.4p5), but Fortran 95 will have an equivalent):

If an external or dummy procedure with an implicit interface is accessed via host association, then it shall have the EXTERNAL attribute in the host scoping unit; if it is invoked as a function in the inner scoping unit, its type and type parameters shall be established in the host scoping unit. The type and type parameters of a function with the EXTERNAL attribute are established in a scoping unit if that scoping unit explicitly declares them, invokes the function, accesses the function from a module, or accesses the function from its host where its type and type parameters are established.

Of course explicit interfaces (best using modules) are much better than external functions.