mathcat

mathcat is an expression evaluating library and REPL in Go with basic arithmetic, functions, variables and more.

Features

mathcat doesn't just evaluate basic expressions, it has some tricks up its sleeve. Here's a list with some of its features:

• Hex literals (0xDEADBEEF)
• Binary literals (0b1101001)
• Octal literals (0o126632)
• Scientific notation (24e3)
• Variables (with UTF-8 support)
• Functions (list)
• Bitwise operators
• Relational operators
• Some handy predefined variables
• Its own REPL

Installation

Library

go get github.com/soudy/mathcat

REPL

go get github.com/soudy/mathcat/cmd/mc

REPL usage

The REPL can be used by simply launching mc:

mc> 8**8
16777216
mc> (8**8) - e # Look, a comment!
16777213.28

Or it can read from stdin like so:

echo "3**pi * (6 - -7)" | mc

Arguments

Name	Description	Default
precision	decimal precision used in results	6
mode	type of literal used as result. can be number, hex, binary or octal	number

Library usage

There are three different ways to evaluate expressions, the first way is by calling Eval, the second way is by creating a new instance and using Run, and the final way is to use Exec in which you can pass a map with variables to use in the expression.

Eval

If you're not planning on declaring variables, you can use Eval. Eval will evaluate an expression and return its result.

res, err := mathcat.Eval("2 * pi * 5") // pi is a predefined variable
if err != nil {
    // handle errors
}
fmt.Printf("Result: %f\n", res) // Result: 31.41592653589793

Run

You can use Run for a more featureful approach. With this method you can assign and use variables across the Parser instance.

p := mathcat.New()
p.Run("a = 1")
p.Run("b = 3")
res, err := p.Run("a + b * b") // 10

Exec

To pass external variables to an expression without using Run, you can use Exec to pass a map of variables.

res, err := mathcat.Exec("a + b * b", map[string]float64{
    "a": 1,
    "b": 3,
}) // 10

Besides evaluating expressions, mathcat also offers some other handy functions.

GetVar

You can get a defined variable at any time with GetVar.

p := mathcat.New()
p.Run("酷 = -33")
if val, err := p.GetVar("酷"); !err {
    fmt.Printf("%f\n", val) // -33
}

IsWholeNumber

Check if a float64 is a whole number.

if mathcat.IsWholeNumber(res) {
    fmt.Printf("%d\n", int64(res))
} else {
    fmt.Printf("%f\n", res)
}

IsValidIdent

Check if a string qualifies as a valid identifier

mathcat.IsValidIdent("a2") // true
mathcat.IsValidIdent("6a") // false

Supported operators

Operator	Description
=	assignment
+	addition
-	subtraction
/	division
*	multiply
**	power
%	remainder
&	bitwise and
|	bitwise or
^	bitwise xor
<<	bitwise left shift
>>	bitwise right shift
~	bitwise not
==	equal
!=	not equal
>	greater than
>=	greater than or equal
<	less than
<=	less than or equal

All of these except ~ and relational operators also have an assignment variant (+=, -=, **= etc.) that can be used to assign values to variables.

Functions

mathcat has a big list of functions you can use. A function call is invoked like in most programming languages, with an identifier followed by a left parentheses like this: max(5, 10).

Function	Arguments	Description
abs	1	returns the absolute value of given number
acos	1	returns the arccosine of given number, in radians
sin	1	returns the sine of given number
cos	1	returns the cosine of given number
tan	1	returns the tangent of given number
asin	1	returns the arcsine of given number
acos	1	returns the acosine of given number
atan	1	returns the arctangent of given number
ceil	1	function returns the smallest integer greater than or equal to a given number
floor	1	returns the largest integer less than or equal to a given number
log	1	returns the natural logarithm of given number
max	2	returns the larger of the two given numbers
min	2	returns the smaller of the two given numbers
sqrt	1	returns the square root of given number
rand	0	returns a random float between 0.0 and 1.0
fact	1	returns the factorial of given number
list	0	list all functions

Predefined variables

There are some handy predefined variables you can use (and change) throughout your expressions:

• pi
• tau
• phi
• e

Documentation

For a more technical description of mathcat, see here.

License

This project is licensed under the MIT License. See the LICENSE file for the full license.