Compact if check involving multiple strings in Fortran [duplicate] - if-statement

This question already has an answer here:
How to check if Fortran array contains value?
(1 answer)
Closed 2 years ago.
Is there a way to check if a string is equal to any of the list together instead of individually explicitly check with a ==? For example,
if(color=='violet' .or. color=='indigo' .or. color=='blue' .or.&
color=='green' .or. color=='yellow' .or. color=='orange' .or. color=='red') then
print *, "It is a rainbow color"
end if
Is there a way compact way to do this? Something like if(color=='violet|indigo|blue|green|yellow|orange|red') ?


You can put the colors into an array and use any.
if (any(color == [character(6) :: "violet","indigo","blue","green","yellow","orange","red"]))

Related

what is the specific usecase for !! in C++ [duplicate]

This question already has answers here:
Double Negation in C++
(14 answers)
Closed 2 years ago.
Came across using !! in C++ during condition check
if ( !! (flag != 0 )){..
}
This could be directly used like
if( flag != 0 ){..
}
Is there any specific corner use case in C/C++ or is it just a form of coding style ?

In this case, it's superfluous, but in general this style is used to convert the actual expression value to
an integer type in C.
a boolean type in C++.

Variable dependent formatting in Fortran90 [duplicate]

This question already has answers here:
Format string for output dependent on a variable
(4 answers)
Closed 2 years ago.
I am trying to understand "variable dependent formatting", specifically where the repeat count in FORTRAN format statement is a variable instead of a fixed number. I have gone through one of the similar questions here, where this is addressed by defining a format variable. I have tried to implement a similar type of test code but I get a run-time error saying "Fortran runtime error: Missing initial left parenthesis in format". I am attaching the code that I have. Could you please let me know where I am going wrong.
Thank you
program main
implicit none
integer num,i
real,dimension(:),allocatable :: logar
character(len = 100) fmt
print*, "enter any number"
read*,num
allocate(logar(num))
do i = 1,num
logar(i) = log(i/3.14)
end do
open(unit=200,file="num.txt",status="unknown")
write(fmt,'( I4,"(f10.5)" )') num
print*,fmt
write(200,fmt) (logar(i),i=1,num)
end program

Change
write(fmt,'( I4,"(f10.5)" )') num
to
write(fmt,'(a, I4,"(f10.5)",a )') '(', num, ')'
Else, you are missing the parenthesis in fmt. Formats strings are delimited by parentheses.

Fortran77: what does the asterisk (*) means in subroutine argument? [duplicate]

This question already has answers here:
What is * in FORTRAN 77
(1 answer)
How can a scalar be passed to a vector (1D array) to a Fortran subroutine?
(2 answers)
Closed 3 years ago.
I have some problem with scipy.interpolate.splrep, so I have no choice by to dig into some very old Fortran77 code.
And one thing I can not understand is here:
https://github.com/scipy/scipy/blob/master/scipy/interpolate/fitpack/curfit.f#L257
it calls a subroutine fpcurf
call fpcurf(iopt,x,y,w,m,xb,xe,k,s,nest,tol,maxit,k1,k2,n,t,c,fp,
* wrk(ifp),wrk(iz),wrk(ia),wrk(ib),wrk(ig),wrk(iq),iwrk,ier)
where the wrk is one dimension array
and the signature of fpcurf is
subroutine fpcurf(iopt,x,y,w,m,xb,xe,k,s,nest,tol,maxit,k1,k2,
* n,t,c,fp,fpint,z,a,b,g,q,nrdata,ier)
c ..
c ..scalar arguments..
real*8 xb,xe,s,tol,fp
integer iopt,m,k,nest,maxit,k1,k2,n,ier
c ..array arguments..
real*8 x(m),y(m),w(m),t(nest),c(nest),fpint(nest),
* z(nest),a(nest,k1),b(nest,k2),g(nest,k2),q(m,k1)
integer nrdata(nest)
you can find it at https://github.com/scipy/scipy/blob/master/scipy/interpolate/fitpack/fpcurf.f
And obviously the signature doesn't match (since wrk is array, and wrk[xxx] is a scalar). Can anyone explain why? I noticed that there is a asterisk (*) here, does it mean anything special?
Maybe anyone familiar with Fortran could please take a look at this function and figure out why the call doesn't match the subroutine signature?

Fortran IF loop [duplicate]

This question already has answers here:
Strange label usage for an IF condition in a DO loop [duplicate]
(2 answers)
Closed 9 years ago.
I have a question about some code I'm looking at written in Fortran. The section of the code I'm confused about is written below.
DO 40 LL=1,N
DO 40 I=1,N-1,2
IF((LL-I)*(LL-I-1)*(LL-I*2)*(LL-I+N-2)) 22,21,22
NODO=LL-I+1
IF((LL.EQ.1) .AND. (I.EQ.N-1)) NODO=NODO+N
I don't understand the condition for the first IF statement. It just looks like numbers are being multiplied together but that number isn't checked against anything. Then 3 line numbers are written after the IF statement. Do anyone know what this IF statement is doing? The last IF statement makes sense as a condition is actually being checked. Thanks.

The line
IF((LL-I)*(LL-I-1)*(LL-I*2)*(LL-I+N-2)) 22,21,22
is an arithmetic if statement, which is certainly obsolescent (the Fortran standard term for deprecated) and may even have been removed in the latest language standard(s). If the condition evaluates to a negative number program control branches to the line with the first label (ie 22), if it evaluates to 0 to the second label (21), if to a positive value to the third label (22). As you see the three labels need not all be different.

DATA declaration in Fortran [duplicate]

This question already has an answer here:
what does DATA TKX/2HKX/ mean in fortran?
(1 answer)
Closed 1 year ago.
Does anyone know the meaning of 4HEND in the following line which comes from an old Fortran code?
DATA XHEND / 4HEND /

4HEND is a Hollerith code to represent the character string "END ". In very old FORTRAN, the variable XHEND might even be a 4-byte integer or real used to hold character data. If implicit typing was in effect in this program, XHEND would have been a real. Another recent question with Hollerith codes: Writing both characters and digits in an array

It replaces assignment
XHEND='END '