README.md

cmdCalc

Command-line calculator in C++17 using Top-Down Parsing.

Build

Start by cloning the repository:

$ git clone --recursive https://github.com/knobin/cmdcalc.git

Then use cmake to build the project. For example on unix systems:

$ mkdir build && cd build
$ cmake -G "Unix Makefiles" ..
$ make

It builds the small library CalcEval that contains the parser and cmdCalc which is the application.

Usage

The cmdCalc can be used in two ways, either with REPL:

$ ./cmdCalc
> 1+2+3+4*10/8
11
> 1+3-(-5)*4^2+pi+log10(10)
88.1416

or by providing command-line arguments:

$ ./cmdCalc "1+2+3+4"
10
$ ./cmdCalc "1+2+3+4" "1.05*20"
10
21

Errors

When the parser encounter an error it will provide detailed information:

$ ./cmdCalc "10++10"
Error parsing!
Unexpected token of "plus" at line 1 : 4
10++
---^
Expected '(', identifier or number!

Same with the scanner:

$ ./cmdCalc "10?10"
Error scanning!
Unexpected symbol at line 1 : 3
10?
--^

Grammar

The calculator can understand numbers, symbolic constants, single-argument functions, one unary and five binary operators using the following grammar below.

<expr> ::= <term><expr_tail>

<expr_tail> ::= +<term><expr_tail>
        |   -<term><expr_tail>
        |   <empty>

<term> ::= <factor><term_tail>

<term_tail> ::= *<factor><term_tail>
        |   /<factor><term_tail>
        |   <empty>

<factor> ::= -<value><factor_tail>
        |   <value><factor_tail>

<factor_tail> ::= ^-<value><factor_tail>
        |   ^<value><factor_tail>
        |   <empty>

<value> ::= ( <expr> )
        |   <id>
        |   num

<id> ::= function <value>
        |   constant

Symbolic constants

Currently supported constants are:

Constant	Implementation
pi	3.14159265
e	2.71828183

Example usage:

$ ./cmdCalc
> 2*pi*5
31.4159
> e^e
15.1543

Single-argument functions

The implemented functions are:

Function	Implementation	Computes
log	std::log	Natural (base-e) logarithm of arg
log10	std::log10	Common (base-10) logarithm of arg
exp	std::exp	e raised to the power of arg
sin	std::sin	Sine of arg (in radians)
cos	std::cos	Cosine of arg (in radians)
tan	std::tan	Tangent of arg (in radians)
arcsin	std::asin	Principal value of the arc sine of arg
arccos	std::acos	Principal value of the arc cosine of arg
arctan	std::atan	Principal value of the arc tangent of arg

Example usage:

$ ./cmdCalc
> log(10)
2.30259
> cos(pi)
-1

License

See MIT License.

This project uses third-party dependencies:

• Catch2: A unit testing framework for C++ (licence)