bares's Introduction

Introduction

Basic ARithmetic Expression Evaluator based on Stacks

This program supports:

Integers in a range from -32.786 to 32.767.
Common operators like +, -, /, *, ^ and %.

This programming project implements a simple parser for an EBNF (Extended Backus-Naur Form) grammar.

It also uses my own vector implementation found here.

The objective Information on EBNF grammar may be found here.

Information on recursive descendent parsing may be found here.

The Grammar

The gramar we want to parse represents arithmetic expressions with addition and subtraction of integers.

<expr>            := <term>,{ ("+"|"-"),<term> };
<term>            := "(",<expr>,")" | <integer>;
<integer>         := 0 | ["-"],<natural_number>;
<natural_number>  := <digit_excl_zero>,{<digit>};
<digit_excl_zero> := "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9";
<digit>           := "0"| <digit_excl_zero>;

This grammar accepts expressions like:

"23 + 43 - 0 + -124 - 21"
" 21"
"-21 + -18"
" -54"
"-21 - 23 + 1234"
(2+3) * 8
5 % 2 ^4
(5 % 3) ^4

And rejects expressions like:

2+
3 * d
2 = 3
2.3 + 4
"01 + 3"
" - 3 + 4"
"2 +"
" "
"+2 + 5"
"-02 + 4"
")2 - 4"
"((2%3) * 8"
"3/(1-1)"

Usage

You will need at least g++ C11 compiler and GNU makefile

to build it simply run:

make

For running Bares execute it like this:

./bares input_file [output_file]

If you just want to give it a try, there is an sample input file inside the data/ directory with all the samples from the project pdf located in the res/ directory.

If no output file is specified this program will write to "output.txt" by default

Authorship

This Program was made by me, Max William, as an exercise for a programming languages course i'm taking in Computer Science at Universidade Federal do Rio Grande do Norte.