Availability of values stored by formatted READ?
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From: Woody on 13 Apr 2010 02:50 When a READ statement is executed, it stores a value in each variable name in its I/O list. Does the standard specify that the values are stored in order, left-to-right? Is it legal to use a value stored by a previous variable in the list? For example INTEGER :: seq,n,v(20),u ! File is opened on unit u for formatted sequential access READ(UNIT=u,"(I3,1X,I3,20I5)") seq,n,(v(i),i=1,n) uses the value of n read in by the same statement.
From: m_b_metcalf on 13 Apr 2010 04:10 On Apr 13, 8:50 am, Woody <ols6...(a)sbcglobal.net> wrote: > When a READ statement is executed, it stores a value in each variable > name in its I/O list. Does the standard specify that the values are > stored in order, left-to-right? Is it legal to use a value stored by a > previous variable in the list? > > For example > > INTEGER :: seq,n,v(20),u > ! File is opened on unit u for formatted sequential access > READ(UNIT=u,"(I3,1X,I3,20I5)") seq,n,(v(i),i=1,n) > > uses the value of n read in by the same statement. Yes, that is legal (see also 'Fortran 95/2003 Explained', Section 9.15). Regards, Mike Metcalf
From: Arjen Markus on 13 Apr 2010 04:54 On 13 apr, 10:10, m_b_metcalf <michaelmetc...(a)compuserve.com> wrote: > On Apr 13, 8:50 am, Woody <ols6...(a)sbcglobal.net> wrote: > > > When a READ statement is executed, it stores a value in each variable > > name in its I/O list. Does the standard specify that the values are > > stored in order, left-to-right? Is it legal to use a value stored by a > > previous variable in the list? > > > For example > > > INTEGER :: seq,n,v(20),u > > ! File is opened on unit u for formatted sequential access > > READ(UNIT=u,"(I3,1X,I3,20I5)") seq,n,(v(i),i=1,n) > > > uses the value of n read in by the same statement. > > Yes, that is legal (see also 'Fortran 95/2003 Explained', Section > 9.15). > > Regards, > > Mike Metcalf Mind you: you do not check that n is within a valid range then. You could achieve that via: READ(UNIT=u,"(I3,1X,I3,20I5)") seq,n,( v(i), i=1,min(n,size(v)) ) Regards, Arjen
From: robin on 13 Apr 2010 05:03 "Woody" <ols6000(a)sbcglobal.net> wrote in message news:89b43a65-4fce-4a0f-8ccf-3755148348a6(a)k33g2000yqc.googlegroups.com... | When a READ statement is executed, it stores a value in each variable | name in its I/O list. Does the standard specify that the values are | stored in order, left-to-right? Yes. You couldn't get anywhere otherwise. | Is it legal to use a value stored by a | previous variable in the list? Yes. Values are stored as soon as requested bt Format control. | For example | | INTEGER :: seq,n,v(20),u | ! File is opened on unit u for formatted sequential access | READ(UNIT=u,"(I3,1X,I3,20I5)") seq,n,(v(i),i=1,n) | | uses the value of n read in by the same statement. That is a traditional way to read an array.
From: robin on 13 Apr 2010 05:07
"Arjen Markus" <arjen.markus895(a)gmail.com> wrote in message news:ff82905d-ace2-4cd9-84f9-b995ca6f4da2(a)35g2000yqm.googlegroups.com... On 13 apr, 10:10, m_b_metcalf <michaelmetc...(a)compuserve.com> wrote: > On Apr 13, 8:50 am, Woody <ols6...(a)sbcglobal.net> wrote: > > > When a READ statement is executed, it stores a value in each variable > > name in its I/O list. Does the standard specify that the values are > > stored in order, left-to-right? Is it legal to use a value stored by a > > previous variable in the list? > > > For example > > > INTEGER :: seq,n,v(20),u > > ! File is opened on unit u for formatted sequential access > > READ(UNIT=u,"(I3,1X,I3,20I5)") seq,n,(v(i),i=1,n) > > > uses the value of n read in by the same statement. > > Yes, that is legal (see also 'Fortran 95/2003 Explained', Section > 9.15). > > Regards, > > Mike Metcalf >Mind you: you do not check that n is within a valid range then. >You could achieve that via: >READ(UNIT=u,"(I3,1X,I3,20I5)") seq,n,( v(i), i=1,min(n,size(v)) ) In his example, yes; but in general, no, of course. It would be still necessary to include an explicit check on the value of N not exceeding the declared upper limit, otherwise some subsequent array reference would come to grief. |