C Library Functions - calculator (3)

NAME

calculator - [M_calculator] parse calculator expression and return numeric or string values (LICENSE:PD)

Synopsis
Description
Options
Examples
See Also
Author
License

SYNOPSIS

subroutine calculator(inline,outlin,mssg,slast,ierr)

   character(len=*),intent=(in)           :: inline
   character(len=iclen_calc),intent=(out) :: outlin
   character(len=iclen_calc),intent=(out) :: mssg
   doubleprecision, intent=(out)          :: slast
   integer, intent=(out)                  :: ierr

DESCRIPTION

CALCULATOR(3f) evaluates FORTRAN-like expressions. It can be used to add calculator-like abilities to your program.

OPTIONS

inline INLINE is a string expression up to (iclen_calc=512) characters long. The syntax of an expression is described in the main document of the Calculator Library.

outlin Returned numeric value as a string when IERR=0.

mssg MSSG is a string that can serve several purposes

o Returned string value when IERR=2

o Error message string when IERR=-1

o Message from ’funcs’ or ’dump’ command when IERR=1

slast SLAST has different meanings depending on whether a string or number is being returned

o REAL value set to last successfully calculated value when IERR=0

o Number of characters in returned string variable when IERR=2

ierr status flag.

-1 An error occurred

0 A numeric value was returned

1 A message was returned

2 A string value was returned

EXAMPLES

Example calculator program

      program demo_calculator
      !compute(1f): line mode calculator program (that calls calculator(3f))
      use M_calculator, only: calculator,iclen_calc
      ! iclen_calc : max length of expression or variable value as a string
      implicit none
      integer,parameter         :: dp=kind(0.0d0)
      character(len=iclen_calc) :: line
      character(len=iclen_calc) :: outlin
      character(len=iclen_calc) :: event
      real(kind=dp)             :: rvalue
      integer                   :: ierr
      ierr=0
      call calculator(’ownmode(1)’,outlin,event,rvalue,ierr)
      ! activate user-defined function interface
      INFINITE: do
         read(*,’(a)’,end=999)line
         if(line.eq.’.’)stop
         call calculator(line,outlin,event,rvalue,ierr)
         select case (ierr)
         ! several different meanings to the error flag returned by calculator
         case(0)
         ! a numeric value was returned without error
           write(*,’(a,a,a)’)trim(outlin),’ = ’,trim(line)
         case(2)
         ! a string value was returned without error
           write(*,’(a)’)trim(event(:int(rvalue)))
         case(1)
         ! a request for a message has been returned (from DUMP or FUNC)
           write(*,’(a,a)’)’message===>’,trim(event(:len_trim(event)))
         case(-1)
         ! an error has occurred
           write(*,’(a,a)’)’error===>’,trim(event(:len_trim(event)))
         case default
         ! this should not occur
           WRITE(6,’(A,i10)’)’*CALCULATOR* UNEXPECTED IERR VALUE ’,IERR
         end select
      enddo INFINITE
      999 continue
      end program demo_calculator

AUTHOR

John S. Urban

LICENSE

Public Domain

Nemo Release 3.1

calculator (3)

February 23, 2025

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