(j3.2006) F2008, ALLOCATE with MOLD

[Bill Long]

Tobias Burnus wrote:
> Hello,
> 
> does the Fortran 2008 draft FDIS (N1814) actually state anywhere what
> MOLD= in the ALLOCATE statement actually does?
> 
> I only find
> 
> R627 alloc-opt  is  ERRMSG = errmsg-variable
>                 or  MOLD = source-expr
>                 or  SOURCE = source-expr
>                 or  STAT = stat-variable
> 
> and later on page 128, paragraph 8:
> 
> "If MOLD= appears and source-expr is a variable, its value need not be
> defined."
> 

The operational text is in the previous subsection, paragraph 5:

If type-spec is specified, each allocate-object is allocated with the 
specified dynamic type and type parameter values; if source-expr is 
specified, each allocate-object is allocated with the dynamic type and 
type parameter values of source-expr; otherwise, each allocate-object is 
allocated with its dynamic type the same as its declared type.


The "if source-expr is specified..." part applies whether it is part of 
  SOURCE= or MOLD=.   Basically, MOLD= has the same effect as SOURCE= 
expect that the allocated object is not assigned a value with MOLD=.


Cheers,
Bill



> 
> Admittedly, the standard does write something about it: In the
> "Introduction" (page xiii, paragraph 2, 5th item):
> 
> "A structure constructor can omit the value for an allocatable
> component. SOURCE= in an ALLOCATE
> statement can give an array variable the bounds as well as the value of
> an expression. MOLD= in an ALLOCATE statement can give a polymorphic
> variable the shape, type, and type parameters of an expression without
> copying the value."
> 
> Is it really intended that only the introduction defines the behaviour?
> 
> Tobias
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-- 
Bill Long                                           longb at cray.com
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