如何在Forth中创建一个基本类和该类的实例?

Question

我想创建一个对象来表示一些电子读数，例如输入电压。为此，我想创建一个基本的类结构来处理不同类型的读数——比如电流和电压。

我想做的伪代码(实际上是Python)是这样的:

# Create base class as a subclass of a common class to all other classes
class PowerReading(object):
    # Defining word to  initialize instance variables using the given input
    def __init__(self, current_value, units):
        # instance variables 
        self.value = current_value
        self.units = units
# Define new class based on our generic class above
class Voltage(PowerReading):
    # Call the parent class word with an input value, and constant units string 
    def __init__(self, current_value):
        super(Voltage, self).__init__(current_value, 'volts')
# Create another class based on the same parent class as Voltage 
class Current(PowerReading):
    def __init__(self, current_value):
        # Call the parent word with current units
        super(Voltage, self).__init__(current_value, 'amps')
# input_voltage_atod() is defined elsewhere: gives an instant reading
# from the ATOD pin on the power input rail, already converted to units of volts.
# Create instance object variable using our new Voltage class. 
input_voltage = Voltage(input_voltage_atod())
# Use the object's instance variables
print input_voltage.value, input_voltage.units
# 3.25 volts

我使用Gforth和oof.fs扩展。

Answer 1

用一些简单的gforth符号:

: symbol ( "name" -- )
  create lastxt , does> ( -- xt ) @ ;
: .symbol ( xt -- )
  >name name>string 1 /string type ;
symbol 'volts
symbol 'amps

这里有一个厕所。

require oof.fs
object class power-reading
  float var value
  cell var units
  method .
how:
  : init ( r-value units -- )  units !  value f! ;
  : . ( -- ) value f@ f.  units @ .symbol space ;
class;
power-reading class voltage
how:
  : init ( r-value -- )  'volts super init ;
class;
power-reading class current
how:
  : init ( r-value -- )  'amps super init ;
class;
3.25e voltage : input-voltage
input-voltage .   Output: 3.25 volts

这很相似，不是吗?

这些天我用mini-oof2。Fs，比Fs低得多，它的作用要小得多。在:

object class
  ffield: value
  field: units
  method init ( value units -- )
  method show ( -- )
end-class power-reading
[: ( r-value units -- )  units !  value f! ;] power-reading to init
[: ( -- ) value f@ f.  units @ .symbol space ;] power-reading to show
power-reading class
end-class voltage
[: ( r-value -- )  value f! 'volts units ! ;] voltage to init
power-reading class
end-class current
[: ( r-value -- )  value f! 'amps units ! ;] current to init
voltage new constant input-voltage
3.25e input-voltage .init
input-voltage .show   Output: 3.25 volts

[: ... ;]不是特殊的mini-oof2。fs语法。他们只是

在这里用作:NONAME的同义词。

.init和.show宏观扩展到>o init o>和>o show o> .

比起使用INIT方法，我经常使用一个非oo单词构造对象:

: >current ( r -- o )
  current new >o  value f!  'amps units !  o o> ;
: current, ( r -- )
  here >o [ current >osize @ ]L allot  value f!  'amps units !  o> ;

当然，这在复杂的面向对象中并不适用以及SUPER方法等等。它是90%的溶液而不是100%的由oof提供的OO解决方案。