Python|函数式编程|公式约束器实现

def make_ternary_constraint(a,b,c,ab,ca,cb):
   #三元约束
    def new_value():
        #通用计算公式,求出第三者连接器
        av,bv,cv=[connector['has_val']()for connector in(a,b,c)]
        if av and bv:
            c['set_val'](constraint,ab(a['val'],b['val']))
        elif av and cv:
            b['set_val'](constraint,ca(c['val'],a['val']))
        elif bv and cv:
            a['set_val'](constraint,cb(c['val'],b['val']))
    def forget_value():
        #对abc三个连接器均使用forget函数
        for connector in(a,b,c):
            connector['forget'](constraint)
    #constraint为调用dictionary,传递message给连接器
    constraint={'new_val':new_value,#表示连接到约束的连接器有了新的值
                'forget':forget_value}#表示连接到约束的连接器需要忘掉它的值
    for connector in(a,b,c):
        #令abc三个连接器均加入约束
        connector['connect'](constraint)
    #返回三元约束
    return constraint

from operator import add,sub

def adder(a,b,c):
    #加法公式的三元约束
    return make_ternary_constraint(a,b,c,add,sub,sub)

from operator import mul,truediv
def multiplier(a,b,c):
    #乘法公式的三元约束
    return make_ternary_constraint(a,b,c,mul,truediv,truediv)

#Connector part
def make_connector(name=None):
    #接受来自约束的消息,name为变量连接器的名称
    informant=None#存储此connector的用户设置约束
    constraints=[]#存储连接器所参与的所有约束(包含公式得出的匿名约束)
    def set_value(source,value):
        nonlocal informant
        val=connector['val']
        if val is None:
            #若不存在值,则设置其为value,informant设置为约束(通过用户设置的约束)
            informant,connector['val']=source,value
            if name is not None:
                print(name,'=',value)
            #对所有约束均调用new_value
            inform_all_except(source,'new_val',constraints)
        else:
            #若传入了不同的值,则发生矛盾
            if val!=value:
                print('Contradiction detected:',val,'vs',value)
    def forget_value(source):
        nonlocal informant
        if informant==source:
            #若informant和约束名称相同(即密码正确且此前未被forget),则将informant和值归0
            informant,connector['val']=None,None
            if name is not None:
                print(name,'is forgotten')
            #对所有约束调用forget_value
            inform_all_except(source,'forget',constraints)
    connector ={'val':None,#当前值
                'set_val':set_value,#表示source请求连接器将当前值设置为该值
                'forget':forget_value,#告诉连接器，source请求它忘掉当前值
                'has_val':lambda: connector['val'] is not None,#返回连接器是否已经有了一个值
                'connect':lambda source:constraints.append(source)}#告诉连接器参与新的约束source
    #连接器 字典 key:string literal, value: function
    return connector

def inform_all_except(source,message,constraints):
    #通知约束来改变所有连接器
    for c in constraints:
        if c!=source:
            c[message]()

def make_converter(c,f):
    #装配连接器和约束条件
    u,v,w,x,y=[make_connector()for _ in range(5)]#五个匿名连接器,9*c=5*(f-32)
    multiplier(c,w,u)#c*9=u
    multiplier(v,x,u)#v*5=u
    adder(v,y,f)#v+32=f
    #根据此连接器,c,f可相互转换
    constant(w,9)#w:9
    constant(x,5)#x:5
    constant(y,32)#y:32

def constant(connector,value):
    #不施加约束,仅设置连接器的值
    constraint={}
    connector['set_val'](constraint,value)
    return constraint

    multiplier(c,w,u)#c*9=u
    multiplier(v,x,u)#v*5=u

    adder(v,y,f)