Wrong behaviour of ISHFT

Hi, I found today that ISHFTing bits to the right does not give the right answer when the first argument is a PARAMETER, as per the following program:

program test_ishft implicit none integer, parameter :: n_par=20 integer :: n=20 integer :: n_double,n_half n_double=ishft(n,1) n_half=ishft(n,-1) print *,n_double,n_half ! correct: prints 40 and 10 n_double=ishft(n_par,1) n_half=ishft(n_par,-1) print *,n_double,n_half ! error: prints 40 and 0 (!!) end program test_ishft

compilation gives no errors:

$ ftn95 test_ishift.f95 [FTN95/Win32 Ver. 8.10.0 Copyright (c) Silverfrost Ltd 1993-2017] Licensed to: Rudnei Dias da Cunha Organisation: UFRGS

NO ERRORS  [<TEST_ISHFT> FTN95 v8.10.0]

but the results given are:

       40          10
       40           0

Also, this is the system I am working on: $ ftn95 /v

Silverfrost FTN95/Win32 Copyright (C) 1993-2017 Silverfrost Ltd
----------------------------------------------------------------

    Version:          8.10.0
    Built:            Sat Feb 11 12:23:39 2017

    Operating System: Windows NT    CPU:              Intel(R) Core(TM) i5-6400T CPU @ 2.20GHz Model 14 Step 3
    CPU Features:     MMX, SSE, SSE2, x86-64

Thanks for looking into it! Cheers Rudnei

This does look like a bug.
Version: 8.30 reproduces this incorrect result.

Ken

I have made a note that this needs investigating.

I have just found out that

n_double=ishft(20,1)
n_half=ishft(20,-1)
print *,n_double,n_half ! error: prints 40 and 0 (!!)

also fails...

This has now been fixed for the next release of FTN95.

(Internally the two cases are the equivalent, both being evaluated at compile time.)

Dear Paul, Many thanks. Cheers Rudnei