CompilerConstruction-ex4/vsl_programs/lexical.vsl

// This program doesn't do anything interesting, it's just to exercise
// most of the lexical entities.

def main() begin                   // def, identifier (func. def.)
    var a, _a1, a_2             // var, identifier, comma operator
    print "Hello, world!"       // print keyword, string literal
	print ""                    // Whitespace: line starts on a tab character
    print "Hello, \"world\"!"   // String literal with escaped double quotes

    _a1 := 10                   // Assignment operator and number constant
    a_2 := 2

    a := _a1 + a_2              // Plus operator
    print _a1, "+", a_2, ":=", a

    a := _a1 - a_2              // Minus operator
    print _a1, "-", a_2, ":=", a

    a := _a1 + (-a_2)           // Parentheses, unary minus operator
    print _a1, "+ (-", a_2, ") :=", a

    a := _a1 * a_2              // Multiply operator
    print _a1, "*", a_2, ":=", a

    a := _a1 / a_2              // Divide operator
    print _a1, "/", a_2, ":=", a

    if a > 0 then               // if, then, FI, single statement
        print a

    // This loop prints the integers 5 through 0, skipping 2
    while a > 0 do              // while/do, block statements
    begin
        if a - 3 > 0 then       // if/then/else/FI
            a := a - 1
        else
        begin
            a := a - 1
            print "Skip..."
            continue            // continue
        end
        print a
    end

    return 0                    // return keyword and number constant
end