Run in Terminal

From the installation, we know that Logica can be executed using:

logica - print Greet <<<'Greet(greeting: "Hello world!")'

However, in logic programming, it is more common to run a file instead of a string as shown above.

run

To execute a file, we can create a file named test.l with the following content:

Greet("hello world");

CAUTION

Ensure to add the ; to indicate the end of the statement.

Then, running the command logica <filename> run <predicate name>

logica test.l run Greet

will produce the following output:

+-------------+
|    col0     |
+-------------+
| hello world |
+-------------+

run_in_terminal

You can also run the file test.l in the terminal using:

logica test.l run_in_terminal Greet

CAUTION

If you are using the installed Logica locally, you might encounter a Google authentication error because it uses Google BigQuery as the default engine. The simplest way to fix this is to add @Engine("sqlite"); to enforce the use of SQLite.

You might be wondering about the difference between run_in_terminal and run. run is designed for newcomers who don't need the advanced capabilities of Logica. Here's a simple example run_diff.l:

@Recursive(N, 100, iterative: true);
N() = 0;
N() = N() + 1;

Using run will produce the following result:

+--------------+
| logica_value |
+--------------+
|            8 |
|            7 |
|            6 |
|            5 |
|            4 |
|            3 |
|            2 |
|            1 |
|            0 |
+--------------+

In contrast, using run_in_terminal will produce:

╥  ▚  N_ifr0 (0 ms)          
╨╥ ▚  N_ifr1 (0 ms)          
╥╨ ▚  N_ifr2 (0 ms)          
╨╥ ▚  N_ifr3 (0 ms) 48 / 48
╥╨ ▚  N_ifr4 (0 ms) 48 / 48
╨╥ ▚  N_ifr5 (0 ms)          
 ╨ ▚  N (0 ms)          
[     Execution complete.      ]  99.01% complete.
+--------------+
| logica_value |
+--------------+
| 100          |
| 99           |
| 98           |
| 97           |
| 96           |
| 95           |
| 94           |
| 93           |
...

The main difference is that run_in_terminal supports complete iterations.

TIP

In most cases, we recommend using run_in_terminal to perform your task.