StackConverter.java

/**
 * StackConverter – JNI bridge to the C library.
 *
 * The native library (libstackconverter.so / stackconverter.dll) must be
 * on java.library.path.  Run with:
 *   java -Djava.library.path=./lib lab5.StackConverterGUI
 */
public class StackConverter {

    static {
        System.loadLibrary("stackconverter");
    }

    /**
     * Convert an infix expression to postfix (Reverse Polish) notation.
     * Unary minus is represented as '~' in the output.
     *
     * @param infix  e.g. "a+b*c"  or  "-a*b^2-c-(-b)"
     * @return postfix string, or a message starting with "ERROR:"
     */
    public native String toPostfix(String infix);

    /**
     * Convert an infix expression to prefix (Polish) notation.
     *
     * @param infix  e.g. "a+b*c"
     * @return prefix string, or a message starting with "ERROR:"
     */
    public native String toPrefix(String infix);

    /**
     * Evaluate an infix expression given variable values.
     *
     * @param infix  the infix expression
     * @param vars   comma-separated assignments, e.g. "a=1,b=2,c=3"
     * @return numeric result as a string, or a message starting with "ERROR:"
     */
    public native String evaluate(String infix, String vars);
}