constructbettertree.f90

Recursive Function Construct_Tree(expression) result(return_tree)
    stack, intent(inout) :: expression
    treenode :: left_exp, right_exp, return_tree
    character :: symbol, op_symbol, closeparen
    ! some better pseudocode
    symbol = pop(expression)

    IF symbol == "(" 
        left_exp = construct_tree(expression)

        op_symbol = pop(expression)

        if op_symbol != operator
            print error and exit
        end if

        right_exp = construct_tree(expression)
        
        closeparen = pop(expression)
        if closeparen != ")" then
            print error and exit
        end if

        RL(return_tree) = right_exp
        LL(return_tree) = left_exp
        INFO(return_tree) = op_symbol
    ElSE IF symbol == a number
        RL(return_tree) = null
        LL(return_tree) = null
        INFO(return_tree) = symbol
    ELSE
        print error and exit (expected '(' or number)
    ENDIF
END FUNCTION Construct_Tree



! Note: this pseudo-code is NOT mine
! @author: Kiwi
! @url: http://kiwi.archuser.com/about-me