ceval
A C/C++ header for parsing and evaluation of arithmetic expressions.
[README file is almost identical to that of the ceval 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 ceval. Parenthesis 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
 Singleargument functions
exp()
, sqrt()
, cbrt()
, sin()
, cos()
, tan()
, asin()
, acos()
, atan()
, sinh()
, cosh()
, tanh()
, abs()
, ceil()
, floor()
, log10()
, ln()
, deg2rad()
, rad2deg()
, signum()
, int()
, frac()
, fact()
 Twoargument functions
pow()
, atan2()
, gcd()
, hcf()
, lcm()
, log()
(generalized log(b, x) to any base b
)
 Predefined math constants
_pi
, _e
...predefined 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 give3
;4,3,0
would be equal to0
; andcos(_pi/2,_pi/3,_pi)
would returncos(_pi)
i.e,1
e
(eoperator for scientific notation) Using the binarye
operator, we can use scientific notation in our arithmetic expressions Ex:0.0314
could be written as3.14e2
;1230000
could be subsituted by1.23e6
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 oddintegral 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 Cprogram, you might require the lm
flag to link math.h
gcc file.c lm