Question

我想生成一个函数<c:if test="#{beanMb.beanList.size() gt 0 }"> ....code </c:if>，它在其闭包中保留变量f，如下所示：

正如您所看到的，function g(a::Vector{Int}) gf = quote x = $a function test() b = 0 for i in eachindex(x) b += i end b end end eval(gf) end f = g([1,2,3,4]) @code_warntype f() Variables: b::ANY #s41::ANY i::ANY Body: begin # In[21], line 6: b = 0 # In[21], line 7: GenSym(0) = (Main.eachindex)(Main.x)::ANY #s41 = (top(start))(GenSym(0))::ANY unless (top(!))((top(done))(GenSym(0),#s41)::ANY)::ANY goto 1 2: GenSym(1) = (top(next))(GenSym(0),#s41)::ANY i = (top(getfield))(GenSym(1),1)::ANY #s41 = (top(getfield))(GenSym(1),2)::ANY # In[21], line 9: b = b + i::ANY 3: unless (top(!))((top(!))((top(done))(GenSym(0),#s41)::ANY)::ANY)::ANY goto 2 1: 0: # In[21], line 11: return b end::ANY效率有点低，因为类型推断无法告诉f，i的类型，我怀疑这些类型由于缺少{{1}的类型推断1}}。

有没有办法改善它？

Answer 1

虽然在函数eval中调用了g，但它会在全局上下文中计算gf。在全局上下文中，类型推断对于变量来说更难。将值定义为const可改善情况。在您的示例中：

function g(a::Vector{Int})
    newvar= gensym("t")
    gf = quote
        const $newvar = $a
        function test() 
            b = 0
            for i in eachindex($newvar)
                b += i
            end
            b
        end
    end
    eval(gf)
end

提供更好的类型变量。来自@code_warntype f()：

Variables:
   b::Int64
   #s2::Int64
   i::Int64

如何在闭包中提供变量类型？

1 个答案: