ceval

A C/C++ header for parsing and evaluation of arithmetic expressions.

[README file is almost identical to that of the <a href=”https://github.com/erstan/ceval#readme”>ceval</a> library]

Functions accessibe from main()

Function	Argument(s)	Return Value
ceval_result()	A mathematical expression in the form of a character array or a CPP string	The result of the expression as a floating point number
ceval_tree()	A mathematical expression in the form of a character array or a CPP string	The function prints the parse tree with each node properly indented depending on it's location in the tree structure

Supported expressions

Any valid combination of the following operators and functions, with floating point numbers as operands can be parsed by <b>ceval</b>. Parentheses can be used to override the default operator precedences.

• Arithematic operators

+ (addition), - (subtraction), * (multiplication), / (division), % (modulo), ** (exponentiation), // (quotient)

• Relational operators

== (equal), != (not equal), < (strictly less), > (strictly greater), <= (less or equal), >= (greater or equal) to compare the results of two expressions

• Single-argument functions

exp(), sqrt(), cbrt(), sin(), cos(), tan(), asin(), acos(), atan(), sinh(), cosh(), tanh(), abs(), ceil(), floor(), log10(), ln(), deg2rad(), rad2deg(), signum(), int(), frac(), fact()

• Two-argument functions

pow(), atan2(), gcd(), hcf(), lcm(), log() (generalized log(b, x) to any base b)

• Pre-defined math constants

_pi, _e

…pre-defined constants are prefixed with an underscore

• Logical operators

&&, || and !

• Bitwise operators

&, |, ^, <<, >>, ~

• Other operators
  • , (Comma operator) Comma operator returns the result of it’s rightmost operand Ex: 2,3 would give 3; 4,3,0 would be equal to 0; and cos(_pi/2,_pi/3,_pi) would return cos(_pi) i.e, -1
  • e (e-operator for scientific notation) Using the binary e operator, we can use scientific notation in our arithmetic expressions Ex: 0.0314 could be written as 3.14e-2; 1230000 could be subsituted by 1.23e6

Usage

Include the ceval library using the #include "PATH_TO_CEVAL.H" directive your C/C++ project.

The code snippet given below is a console based interpreter that interactively takes in math expressions from stdin, and prints out their parse trees and results.

//lang=c
#include<stdio.h>
#include<stdlib.h>

#include "ceval.h"

int main(int argc, char ** argv) {
  char expr[100];
  while (1) {
    printf("In = ");
    fgets(expr, 100, stdin);
    if (!strcmp(expr, "exit\n")) {
      break;
    } else if (!strcmp(expr, "clear\n")) {
      system("clear");
      continue;
    } else {
      ceval_tree(expr);
      printf("\nOut = %f\n\n", ceval_result(expr));
    }
  }
  return 0;
}

Test Run

In = 3*7**2
                2
        **
                7
*
        3

Out = 147.000000


In = (3.2+2.8)/2
        2
/
                2.80
        +
                3.20

Out = 3.000000


In = _e**_pi>_pi**_e
                2.72
        **
                3.14
>
                3.14
        **
                2.72

Out = 1.000000


In = 5.4%2
        2
%
        5.40

Out = 1.400000


In = 5.4//2
        2
//
        5.40

Out = 2.000000


In = 2*2.0+1.4
        1.40
+
                2
        *
                2

Out = 5.400000


In = (5/4+3*-5)+(sin(_pi))**2+(cos(_pi))**2
                2
        **
                        3.14
                cos
+
                        2
                **
                                3.14
                        sin
        +
                                        5
                                -
                        *
                                3
                +
                                4
                        /
                                5

Out = -12.750000


In = 3,4,5,6
        6
,
                5
        ,
                        4
                ,
                        3

Out = 6.000000


In = tanh(2/3)==(sinh(2/3)/cosh(2/3))
                                3
                        /
                                2
                cosh
        /
                                3
                        /
                                2
                sinh
==
                        3
                /
                        2
        tanh

Out = 1.000000


In = (2+3/3+(3+9.7))
                9.70
        +
                3
+
                        3
                /
                        3
        +
                2

Out = 15.700000


In = sin(_pi/2)+cos(_pi/2)+tan(_pi/2)
                        2
                /
                        3.14
        tan
+
                                2
                        /
                                3.14
                cos
        +
                                2
                        /
                                3.14
                sin

[ceval]: tan() is not defined for odd-integral multiples of _pi/2

Out = nan


In = asin(2)
        2
asin

[ceval]: Numerical argument out of domain

Out = nan


In = exit
... Program finished with exit code 0

Note

When the ceval.h file is included in a C-program, you might require the -lm flag to link math.h

gcc file.c -lm