In Fortran, each time one uses WRITE a new line is produced. In order to control the working of a program that is being executed, I would like to write on screen the current value of a variable, but always on the same line (erasing the previous value and starting at the beginning of the line). That is, something like
1 CONTINUE
"update the value of a"
WRITE(*,*) a
BACKSPACE "screen"
GOTO 1
Something like WRITE(*,*,ADVANCE='NO') (incorrect anyway) is not quite what I
need: this would write all the values of a one after another on a very long
line.
A trick that I was shown for what you want is as follows
do l=1,lmax
...update a...
write(*,'(1a1,<type>,$)') char(13), a
enddo
where <type> is your format specifier for a (i.e., i0 for integer).
The key is the char(13), which is the carriage return, and the $ in the format descriptor. I really don't know if there is a name for $, I just know that it works for displaying on the screen--for output to file you get an a on each line.
Related
I have large text files with about 6 lines/instances of 3_xcalc_59 in which 59 is some 2-digit integer.
I am looking to increment these values of the text file by 1 every time I run the program.
I know I can increment a value defined in the code, but how can I increment an integer inside a line of text?
I was thinking the first part of the process would involve reading these lines and assigning them to string variables or a list, but I am not sure how to even do that.
I can find the lines by writing if line.startswith("3_xcalc") , but I'm not sure how to assign them to a list.
Simply writing
for line in open(inputfile, "w"):
line.startswith("3_xcalc") = listoflinesstartingwith3xcalc
Tells me "can't assign to function call", so that doesn't work, but I'm not sure what else to try.
Thank you.
I have little knowledge of the Fortran language. I have come across some programs written in the 90s (see attached snapshot showing just a portion of a long script).
I'd like to know what kind of compiler is appropriate to execute such codes? I have installed gfortran-4.2.3 on my mac. I'm also not sure about the indentation in the attached code: if C (comment) is at column 1, does the main code start at column 9 or 7? what about the position of numbers placed in between referred by GO TO?
This is not Fortran 90. This is Fortran 77.
That said, gfortran is able to compile this code. Make sure that the file extension for the file is .f so that gfortran realises it's fixed-form.
The C needs to be in the first column, the numbers that you reference are labels, they can be between column 1 and 5. The asterisk at line 198 is a continuation character, meaning that this should be treated as part of the previous line. It must be in column 6. Everything else needs to be between columns 7 and 72 (inclusive)
Oh, and the 3-digit numbers at the very beginning are line numbers, and must not be in the source code.
Edited to add: Since you have to type it all again anyway, you might as well make it free-form:
Replace the C in the first column with !, and change the way continuation lines are marked: Turn this:
write (*, *) "This is some long text,
* which doesn't fit into a line"
Into this:
write(*, *) "This is some long text, " // &
"which doesn't fit into a line"
Everything else can stay like it is. (You can now use proper indentation, too!)
New Edit
So you've pasted the code that you wrote and the error messages, so I'm replying to that now.
In Fixed Form, any character past column 72 is ignored. You have a few lines with long strings, where the terminating quotation mark is in that ignored region.
Make sure that no line exceeds the 72nd row.
I've been given the challenge to port a Fortran 77 program into C#.
I've found out that read(5,*) read from the standard input, i.e. the keyboard.
Now I'm trying to understand how the following works:
1. When I run the program, I have to run it as cheeseCalc<blue.dat>output.txt
, which read a blue.dat file and produces a output.txt file. How does read work in this case?
In the same program, there is READ(5,* )IDUM and later it also has read(5,*)idum,idum,tinit. What is happening in this case?
The blue.dat file has the following lines:
HEAD make new cake
INPUT VARIABLES
MFED MASS-FEED 30 ;1001 1 100 PEOPLE TO FEED
TOVE TEMP-IN-OVEN 150.0 ;1001 20 100 TEMPERATURE OF OVEN, C
UPDATED: Just for context, the initial lines of code in the program are:
program cheeseCalc
CHARACTER*76 IDENT
CHARACTER*1 IDUM
READ(5,104)IDENT
104 FORMAT(4X,A)
READ(5,*)IDUM
c write start record
write(6,102)IDENT
102 format('**START',/,4X,A,/)
read(5,*)idum,idum,frate
110 format(f10.0)
frate2=frate/3.6
read(5,*)idum,idum,tempo
* Do calculation *
write(6,*)frate2,tempo
end
Any help will be appreciated!! Thanks!
The full detail of the general read statement is documented elsewhere, but there is an idiom here which is perhaps worth elaborating on.
The statement read(5,*) ... is list-directed input from the external unit number 5. Let's assume (it's not guaranteed, but it's likely and you seem happy with that for your setup) that this external unit is standard input.
The idiomatic part is the repeated use of a single variable in an input list such as
read(5,*) idum, idum, ...
This (and the fact that idum is an (awfully named) length-1 character variable) signifies that the user doesn't care about the input in the first two fields). The first string, delimited by blanks, is read then the first character is assigned to idum. Then idum is immediately set to the first character of the next string.
The purpose of this is to set the place in the record to the third field, which is read into the (real) variable frate (in the first case).
Equally
read(5,*) idum
is just skipping the second line (strictly, reading the first character, but that's not used anywhere before the next read into idum): the first blank-delimited field is read but the next read moves on to the next line rather than continuing with that one.
Suppose I have the following code
program fortran
open(900, FILE='SOMETHING')
write(900, *) '21'
end program fortran
The file form will be
21
that is, there is a space before the number. How to get rid of that space?
You can write it as a string:
PROGRAM fortran
OPEN(900,FILE='SOMETHING')
WRITE(900,'(a)') '21'
END PROGRAM FORTRAN
> cat SOMETHING
21
To respond to the comment:
The more explicit way of doing that would be to write the number into a string (you could also use list-directed I/O for this step), remove whitespaces from the string trim and finally output the left-adjusted adjustl:
program test
character(len=23) :: str
write(str,'(ES23.15 E3)') 1.23d0
write(*,'(a)') adjustl(trim(str))
write(str,'(ES14.7 E2)') 0.12e0
write(*,'(a)') adjustl(trim(str))
end program
> ./a.out
1.230000000000000E+000
1.2000000E-01
This solution is probably more complicated then necessary, but it is a very flexible approach that can be extended easily for arbitrary purposes and formats.
In list-directed format (the * in write(unit,*)) the compiler typically inserts a leading space. The first column used to be used to control line printers but that is now deleted from Fortran.
You can use any explicit format you want to get rid of the leading space. For example the general g0 one or the string specific a or the integer-specific i.
The program can run, I am not sure how to use open() and save the data in another external file name output.txt. My questions are stated below - please have a look and help.
program start
implicit none
integer ::n
real(kind=8)::x,h,k
real(kind=8),external:: taylorq
x=1.0
n=20
h=exp(x)
k=taylorq(x,n)
open(10,'output.txt') ----------- *question1:(when should i put this open file?)*
write(*,*)"The exact value=",h
write(*,*)"The approximate value=",k
write(*,*)"The error=",h-k
end program start
function taylorq(x,n)
implicit none
integer::n,i
real(kind=8):: x,taylor,taylor2,taylorq,h
h=exp(x)
taylor=1.
taylor2=taylor
write(*,*)"i exact appro error"-----------question2:(actually I want to draw a table with subtitle i, exact, appro, error in each column, is there a nice way to arrange them like eg.we can use %5s)
do i=1,n
taylor=taylor*x/i
taylor2=taylor2+taylor
write(10,*)i,h,taylor2,taylor2-h --------question3:*(I want to save the data written here into file output.txt)*
end do
close(10)
taylorq=taylor2
end function taylorq
1. where to open
You should put open(10,...) so it executes before any write(10,...) -- or read(10,...) if this was input.
Since your writes occur in the function taylorq, you should open() before the statement that calls taylorq.
For programs that do very large computations, which Fortran is suited/famous for, it is often best to do
all file open's very near the beginning of the program, so that if there is a problem opening any file,
it is caught and fixed without wasting hours or days of work. But your program is much simpler than that.
2. formatting
Yes, Fortran can do formatted output -- and also formatted input. Instead of a text string with
interpolated specifiers (like C and the C part of C++, and Java, and awk and perl and shell) it uses specifiers
with optionally interpolated text values, and the specifiers are written with the format letter on
the left followed by the width (almost always) and other parameters (sometimes).
You can either put the format directly in the WRITE (or READ) statement, or in a separate FORMAT
statement referred to by its label in the I/O statement.
write (10, '(I4,F10.2,F10.2,F10.2)' ) i,h,taylor2,taylor2-h
or
write (10, 900) i,h,taylor2,taylor2-h
! this next line can be anywhere in the same program-unit
900 format (I4,F10.2,F10.2,F10.2)
Unlike C-family languages, Fortran will always output the specified width; if the value doesn't fit,
it prints asterisks ***** instead of forcing the field wider (and thus misaligned) (or truncating as
COBOL does!). Your series grows fast enough you might want to use scientific notation like E10.3.
(The format letters can be in either case, but I find them easier to read in upper. YMMV.)
There are many, MANY, more options. Any textbook or your compiler manual should cover this.