# 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. 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
#include

#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`

```shell
gcc file.c -lm 
```