Boolevard

Boolevard is a boolean expression evaluator written in C++ using the interpreter pattern:

               +-------+                  +--------+             +-------------+
expression --> | Lexer | --- [Tokens] --> | Parser | --- AST --> | Interpreter | --> True|False
               +-------+                  +--------+             +-------------+

To compile the code use make (requires g++):

make release

Here's an example of how to use the program in the command line:

./blvrd '3 in [1, 2, 3, 4, 5] or (-2 < 3 and 3 < 5)'
true

Basic types are:

Type	Example
Boolean	True, False
Integers	1, -3, 1000
Decimals	1.2, -0.5
Strings	"This is a string"
Lists	[1, 2, 3, True, ["a", "b"]]
Ranges	[1..4]

Available operators are:

Operator	Example
not	not
equal	==
not equal	!=
greater	>
less	<
greater or equal	>=
less or equal	<=
contains	contains
starts with	sw
ends with	ew
in	in

Use variables in expression:

./blvrd -a res=`echo 2*6|bc` 'res eq 12'
true

Numeric output:

./blvrd -n 'True'; echo $?
0
./blvrd -n 'False'; echo $?
1

The numeric output is aligned to support the following command line structure:

./blvrd -n 'True' && echo "Hello World!" || echo "Nope"
Hello World!
./blvrd -n 'False' && echo "Hello World!" || echo "Nope"
Nope

Check the test script for more examples.

TODOs

• Better error handling
• Add more operator alternatives, e.g. < as lt (less than)
• Add XOR operator
• Add ranges
• Use variables in expression