Question

我想显示产品记录列表的价格范围。

假设我有这个产品清单，其中包含金额/价格的二进制值。

Products = [#product{amount=<<"20.21">>}, #product{amount=<<"30.21">>}, #product{amount=<<"9.21">>}]

我的目标是显示最小 - 最大价格范围，例如：＆LT;＆LT; “9.21” ＆GT;＆GT; - ＆lt;＆lt;“30.21”＆gt;＆gt;

怎么可以在这里继续？

Answer 1

-module(my).
-compile(export_all).
-record(product, {name, price}).

products() ->
    [
        #product{name='a', price= <<"20.21">>}, 
        #product{name='b', price= <<"30.21">>}, 
        #product{name='c', price= <<"9.21">>},
        #product{name='d', price= <<"11.21">>}
    ].

price_range(Products) ->

    PriceFunc = fun(Product, {Min, Max}) ->
                    Price = binary_to_float(Product#product.price),
                    NewMin = min(Min, Price),
                    NewMax = max(Max, Price),
                    {NewMin, NewMax}
                end,

    InitPrice = binary_to_float(
                  (hd(Products))#product.price
                ),

    lists:foldl(PriceFunc, {InitPrice, InitPrice}, Products).

在shell中：

9> c(my).                   
my.erl:2: Warning: export_all flag enabled - all functions will be exported
{ok,my}

10> Products = my:products().
[{product,a,<<"20.21">>},
 {product,b,<<"30.21">>},
 {product,c,<<"9.21">>},
 {product,d,<<"11.21">>}]

11> my:price_range(Products).
{9.21,30.21}

Erlang - 以最高价值获取记录并以最低价值记录

1 个答案: