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COMPUTE

Section: C Library Functions (3)
Updated: 16 Mar 1998
Index

NAME

compute, compute_line, compute_answer, compute_define,compute_error - Simple calculator.

SYNTAX

#include <xite/compu4.h>

int compute_line( char* inp_line, ...);

number *compute_answer( void );

char *compute_error( int message );

int compute_define( char* name, func action );

DESCRIPTION

Compute the value of an expression.The value can be of all types. The return valuegives the type of the answer.

#define TY_UN -1  * Unknown, Error  in i_value  *
#define TY_BF 0   * Boolean, false
#define TY_BT 1   * Boolean, true
#define TY_CI 2   * int,     Answer in i_value  *
#define TY_CD 3   * double,  Answer in d_value  *
#define TY_CS 4   * *char,   Answer in p_value  *
#define TY_BO 5   * Boolean, Answer in i_value  *
#define TY_CP 6   * Predefined constant         *
#define TY_VR 7   * Variable                    *

Answer is a numberrecord containing the resultof the expression. Number is defined as:

typedef struct u_tag
{
   union
   {
     INT i_value;
     double d_value;
     char *p_value
   } u_value
   int u_type;
} number;

Line is the string which is evaluated. The line is anarithmetic and/or a boolean expression. Special symbolsintroduced by the character % is converted to a string,or a constant from the argument list. The grammar is

S -> $
S -> E$
E -> un E
E -> E op E
E -> (E)
E -> id = E

$ -  End of line
E -  Input constant.
        %S - The first argument in the list is
             replaced as a character string.
        %s - The next (or second) argument in the list is
             replaced as a character str ing.
        %L - The first argument in the list is
             replaced as a lowercase character string.
        %l - The next (or second) argument in the list is
             replaced as a lowercase character string.
        %U - The first argument in the list is
             replaced as a uppercase character string.
        %u - The next (or second) argument in the list is
             replaced as a uppercase character string.
        %D - The first argument in the list is
             replaced as an integer.
        %d - The next (or second) argument in the list is
             replaced as an integer.
        %F - The first argument in the list is
             replaced as a double precision.
        %f - The next (or second) argument in the list is
             replaced as a double precision.
      Predefined Constant.
        INT    - All integer strings and all integers
        REAL   - All floating-point strings and reals
        FILE   - All strings = name of existing file.
        EXE    - All strings = name of executable file.
        WRITE  - All strings = name of file with write
                 access.
        READ   - All strings = name of file with read
                 access.
        usrdef - Define your own constant
      Result from: un E, E op E, or (E)
un - [+,-]     int, float or string,
                String is converted to INT or float.
      [NOT]     Boolean
op - [*,/]     int, float or string.
                String is converted to INT or float.
                INT op float -> int.
                float op INT -> float.
op - [+,-]     int, float or string.
                String is converted to INT or float.
                 INT op float -> int.
                float op INT -> float.
op - [LT,<,LE,<=,EQ,==,NE,!=,GE,>=,GT,>]
                String is converted to INT or float.
                INT op float -> INT   op INT   -> Boolean.
                float op INT -> float op float -> Boolean.
op   [IS]      True is first argument match the regular
                expresion in arg2. All Predefined
                constants are valid regular expresions.
op - [AND]     Bool op Bool -> Bool. Second argument
                is not computed if first arg is FALSE.
op - [OR]      Bool op Bool -> Bool. Second argument
                is not computed if first arg is TRUE.
() -           Operators abow are listed with decreasing
                precedence.
=              Define variables. Defined variables may
                be used in other expressions.
                A = 4
                B = 2*A

DIAGNOSTICS

The diagnostic code is listed below.

RETURN VALUE

If the evaluation of the expression was sucsessful thefunction returns a non-negative result.If the evaluation fails compute_errorwill return
E_TOK - Undefined token.
E_ARG - Missing argument.
E_OP  - Missing operand.
E_LP  - Too many )'s.
E_EOL - Unexpected end of line.
E_RP  - Expected )
E_TYP - Wrong arg type for op
E_LEN - Too long input line
E_EQ  - Variable expexted

AUTHOR

Otto Milvang

EXAMPLES

ID

$Id: compu4.c,v 1.27 1997/01/29 10:46:18 svein Exp $

--------------------------------------------------------------- */

/*---------------------------------------------------------------

compute - include files

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