Seminar project for Non-procedural Programming, NPRG005 in Summer semester 2022/23
on MFF CUNI.

Author: Tomas Sourada, 3rd year on undergraduate studies of Computer Science,
study field Artificial Intelligence.

Topic: Arithmetic expression parser and evaluator.

Task: Create a Prolog predicate, which takes a string containing an arithmetic
expression written in words in the Czech language, converts it to its
number-operator variant and evaluates it.

Supports usual Czech language, input string tokens separated by space, without
commas. Supports integers written with or without diacritis and usual operators
'+',  '-', '*', '-' and simple parentheses '(', ')'.

Implemented on SWI-Prolog version 8.4.3 for x86_64-linux.
Date of implementation: from 2022-09-09 to 2022-09-14.

Example call:
# Start SWI-prolog:
> swipl
# Compile `main.pl`:
?- [main].
true.
# Run the predicate:
?- evaluateExpressionString("třináct krát tři", Value).

Input string: třináct krát tři
Expression:   13 * 3
Result:       39

Value = 39.

# Run the predicate:
?- evaluateExpressionString("jedna plus dva krát tři minus závorka sedm minus čtyři konec závorky deleno tremi", Value).

Input string: jedna plus dva krát tři minus závorka sedm minus čtyři konec závorky deleno tremi
Expression:   1 + 2 * 3 - ( 7 - 4 ) / 3
Result:       6

Value = 6.