anybody know FORTRAN?

[JewishBacon]

so i have this code that i need to convert to fortran from c. yes i know this is useless because nobody uses fortran or c anymore.

here is the c code

 

#include <stdio.h>#include <math.h>double f(double t, double y){return y;}main(){double h=0.1, t, y, k1,k2,k3,k4;int i;/* initial value */t=0.0;y=1.0;for (i=0; i<=10; i++){printf("t= %lf rk= %lf exact=%lf\n", t, y, exp(t));k1=h*f(t,y);k2=h*f(t+h/2, y+k1/2.0);k3=h*f(t+h/2, y+k2/2.0);k4=h*f(t+h, y+k3);y= y+(k1+2.0*k2+2.0*k3+k4)/6.0;t=t+h;}return 0;}

attached is a screencap of what i think should work, but it does not seem to run. any ideas?

Edited April 29, 2014 by alpenwasser
code tags :)

[Hans Christian | Teri]

No one uses C anymore? I must be living in some parallel universe then.

[JewishBacon]

No one uses C anymore? I must be living in some parallel universe then.

not the point

[IKnowNothinAboutTechnology]

I dont have it

[CornOnJacob]

Many people use C, but far fewer use fortran. Please put your code in code brackets (the icon in between the picture and quote icons) 

like this.

As for your actual problem, sorry, I can't help. Could you explain the output you are trying to get? It will make it easier for others to achieve that result, especially since your code apparently doesn't do what you want.

[JewishBacon]

IM literally just supposed to translate thec code to the fortran code

[JewishBacon]

Many people use C, but far fewer use fortran. Please put your code in code brackets (the icon in between the picture and quote icons) 

like this.

As for your actual problem, sorry, I can't help. Could you explain the output you are trying to get? It will make it easier for others to achieve that result, especially since your code apparently doesn't do what you want.

sorry about that im on my mobile and cant

[RaidenLeeChin]

Shouldn't the function subprogram be:

function F(T, Y)     F=Yend

 

mainly because in the C code it takes two parameters and just returns Y. Which is a useless function though.

[JewishBacon]

@RocK_lee2

this is what my code looks like right now

 

       FUNCTION F(T, Y)       DOUBLE PRECISION F, X,Y       F=Y       RETURN       END       PARAMETER (EPS=1.0E-6)       DOUBLE PRECISION H,K1,K2,K3,K4,T,Y       H=0.1       Y=1.0       T=0.0        DO 10 I=0,10,1        WRITE(*,*)"T=",T        WRITE(*,*)"RK=",Y        WRITE(*,*)"EXACT=",EXP(T)        K1=H*F(T,Y)        K2=H*F(T+H/2, Y+K1/2.0)        K3=H*F(T+H/2, Y+K2/2.0)        K4=H*F(T+H, Y+K3)        Y= Y+(K1+2.0*K2+2.0*K3+K4)/6.0        T=T+H        IF I=10 GOTO 11 10    CONTINUE 11    CONTINUE       STOP       END

and this is what i get when i type g77 fortrancode.f

fort.f: In program `MAIN__':fort.f:1:          FUNCTION F(T, Y)                   1fort.f:18: (continued):           K1=H*F(T,Y)                2Global name `f' at (2) has different type at (1) [info -f g77 M GLOBALS]fort.f:24:           IF I=10 GOTO 11           ^Invalid form for IF statement at (^) 

[MrSuperb]

I know nothing about FORTRAN but ...

IF I=10 GOTO 11

should be ...

 IF (I .EQ. 10) GOTO 11

[JewishBacon]

 

I know nothing about FORTRAN but ...

IF I=10 GOTO 11

should be ...

 IF (I .EQ. 10) GOTO 11

well it appears that you do! haha that fixed the for statement error, but not the other ones

[MrSuperb]

Ignore my previous comment. the whole loop should be different ...

 

instead of this ...

 DO 10 I=0,10,1...bla bla bla ...IF I=10 GOTO 11 10 CONTINUE 11 CONTINUE

do this ...

 DO 10 I=0,10...bla bla bla ...10 CONTINUE 

[JewishBacon]

 

Ignore my previous comment. the whole loop should be different ...

 

instead of this ...

 DO 10 I=0,10,1...bla bla bla ...IF I=10 GOTO 11 10 CONTINUE 11 CONTINUE

do this ...

 DO 10 I=0,10...bla bla bla ...10 CONTINUE 

so this is what i did 

       FUNCTION F(T, Y)       DOUBLE PRECISION F, X,Y       F=Y       RETURN       END       PARAMETER (EPS=1.0E-6)       DOUBLE PRECISION H,K1,K2,K3,K4,T,Y       H=0.1       Y=1.0       T=0.0        DO 10 I=0,10        WRITE(*,*)"T=",T        WRITE(*,*)"RK=",Y        WRITE(*,*)"EXACT=",EXP(T)        K1=H*F(T,Y)        K2=H*F(T+H/2, Y+K1/2.0)        K3=H*F(T+H/2, Y+K2/2.0)        K4=H*F(T+H, Y+K3)        Y= Y+(K1+2.0*K2+2.0*K3+K4)/6.0        T=T+Hc        IF I=10 GOTO 11 10    CONTINUEc 11    CONTINUE       STOP       END

and this is the output, im not sure what its trying to tell me 

fort.f: In program `MAIN__':fort.f:1:          FUNCTION F(T, Y)                   1fort.f:18: (continued):           K1=H*F(T,Y)                2Global name `f' at (2) has different type at (1) [info -f g77 M GLOBALS]

[MrSuperb]

FUNCTION F(T, Y)DOUBLE PRECISION F, X,YF=YRETURNEND

instead:

FUNCTION F(T, Y)F=YEND

[JewishBacon]

FUNCTION F(T, Y)DOUBLE PRECISION F, X,YF=YRETURNEND

instead:

FUNCTION F(T, Y)F=YEND

that still outputs the same errors

[MrSuperb]

    DOUBLE PRECISION FUNCTION F(T, Y) <----------------------    DOUBLE PRECISION F, X,Y    F=Y    END         PARAMETER (EPS=1.0E-6)    DOUBLE PRECISION H,K1,K2,K3,K4,T,Y    DOUBLE PRECISION F <----------------------------------         H=0.1    Y=1.0    T=0.0         DO 10 I=0,10    WRITE(*,*)"T=",T    WRITE(*,*)"RK=",Y    WRITE(*,*)"EXACT=",EXP(T)    K1=H*F(T,Y)    K2=H*F(T+H/2, Y+K1/2.0)    K3=H*F(T+H/2, Y+K2/2.0)    K4=H*F(T+H, Y+K3)    Y= Y+(K1+2.0*K2+2.0*K3+K4)/6.0    T=T+H    c IF I=10 GOTO 11         10 CONTINUE         c 11 CONTINUE         STOP    END     

try this

 

edit: without my nice arrows

[JewishBacon]

    DOUBLE PRECISION FUNCTION F(T, Y) <----------------------    DOUBLE PRECISION F, X,Y    F=Y    END         PARAMETER (EPS=1.0E-6)    DOUBLE PRECISION H,K1,K2,K3,K4,T,Y    DOUBLE PRECISION F <----------------------------------         H=0.1    Y=1.0    T=0.0         DO 10 I=0,10    WRITE(*,*)"T=",T    WRITE(*,*)"RK=",Y    WRITE(*,*)"EXACT=",EXP(T)    K1=H*F(T,Y)    K2=H*F(T+H/2, Y+K1/2.0)    K3=H*F(T+H/2, Y+K2/2.0)    K4=H*F(T+H, Y+K3)    Y= Y+(K1+2.0*K2+2.0*K3+K4)/6.0    T=T+H    c IF I=10 GOTO 11         10 CONTINUE         c 11 CONTINUE         STOP    END     

try this

 

edit: without my nice arrows

 

that gives way more errors than what was there before

[MrSuperb]

does this compile ? with errors?

PROGRAM LTTPARAMETER (EPS=1.0E-6)DOUBLE PRECISION H, K1, K2, K3, K4, T, Y, FH=0.1Y=1.0T=0.0DO 10 I=0,10WRITE(*,*)"T=",TWRITE(*,*)"RK=",YWRITE(*,*)"EXACT=",EXP(T)K1=H*F(T,Y)K2=H*F(T+H/2, Y+K1/2.0)K3=H*F(T+H/2, Y+K2/2.0)K4=H*F(T+H, Y+K3)Y= Y+(K1+2.0*K2+2.0*K3+K4)/6.0T=T+H10 CONTINUESTOPENDDOUBLE PRECISION FUNCTION F(T, Y)DOUBLE PRECISION F,T,YF=YEND

[JewishBacon]

 

does this compile ? with errors?

PROGRAM LTTPARAMETER (EPS=1.0E-6)DOUBLE PRECISION H, K1, K2, K3, K4, T, Y, FH=0.1Y=1.0T=0.0DO 10 I=0,10WRITE(*,*)"T=",TWRITE(*,*)"RK=",YWRITE(*,*)"EXACT=",EXP(T)K1=H*F(T,Y)K2=H*F(T+H/2, Y+K1/2.0)K3=H*F(T+H/2, Y+K2/2.0)K4=H*F(T+H, Y+K3)Y= Y+(K1+2.0*K2+2.0*K3+K4)/6.0T=T+H10 CONTINUESTOPENDDOUBLE PRECISION FUNCTION F(T, Y)DOUBLE PRECISION F,T,YF=YEND

oh yea. loads of em

test.f:7:         DO 10 I=0,10         1test.f:19: (continued):         END         2Statement at (2) invalid in context established by statement at (1)test.f:7:         DO 10 I=0,10         1test.f:20: (continued):         DOUBLE PRECISION FUNCTION F(T, Y)         2Statement at (2) invalid in context established by statement at (1)test.f:3:         DOUBLE PRECISION H, K1, K2, K3, K4, T, Y, F                                             1test.f:20: (continued):         DOUBLE PRECISION FUNCTION F(T, Y)                                     2Invalid declaration of or reference to symbol `t' at (2) [initially seen at (1)]test.f:3:         DOUBLE PRECISION H, K1, K2, K3, K4, T, Y, F                                                1test.f:20: (continued):         DOUBLE PRECISION FUNCTION F(T, Y)                                        2Invalid declaration of or reference to symbol `y' at (2) [initially seen at (1)]test.f:7:         DO 10 I=0,10         1test.f:21: (continued):         DOUBLE PRECISION F,T,Y         2Statement at (2) invalid in context established by statement at (1)test.f:3:         DOUBLE PRECISION H, K1, K2, K3, K4, T, Y, F                                                   1test.f:22: (continued):         F=Y         2Invalid declaration of or reference to symbol `f' at (2) [initially seen at (1)]test.f:7:         DO 10 I=0,10         1test.f:23: (continued):         END         2Statement at (2) invalid in context established by statement at (1)test.f:7:         DO 10 I=0,10         ^

[TheProfosist]

No one uses C anymore? I must be living in some parallel universe then.

Twas exactly what I was about to say.

[MrSuperb]

some slight changes ...

(maybe someone actually knows fortran here )

 

    PROGRAM LTT    PARAMETER (EPS=1.0E-6)    DOUBLE PRECISION H, K1, K2, K3, K4, T, Y, F    H=0.1    Y=1.0    T=0.0    DO 10 I=0,10    WRITE(*,*)'T=',T    WRITE(*,*)'RK=',Y    WRITE(*,*)'EXACT=',EXP(T)    K1=H*F(T,Y)    K2=H*F(T+H/2, Y+K1/2.0)    K3=H*F(T+H/2, Y+K2/2.0)    K4=H*F(T+H, Y+K3)    Y= Y+(K1+2.0*K2+2.0*K3+K4)/6.0    T=T+H    10 CONTINUE    STOP    END    DOUBLE PRECISION FUNCTION F(T, Y)    DOUBLE PRECISION T,Y    F=Y    END

[JewishBacon]

So I figured it out. F needs to be initialized in both the function AMD subfunction

[MrSuperb]

So I figured it out. F needs to be initialized in both the function AMD subfunction

 

you have to declare it, not initialize it ...

 

thats why I wrote :

DOUBLE PRECISION H, K1, K2, K3, K4, T, Y, F

[TechSage]

A lot of people use C, you'd actually be surprised. If you want to be any type of programmer, you should learn C, you can make algorithms with it and stuff.

 

My math teacher and uncle (professor of Computer Science and EE) knows Fortran, COBOL, Pascal and those really old languages that all the modern banks use today.