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Implications of foldr vs. foldl (or foldl')
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The recursion for foldr f x ys where ys = [y1,y2,...,yk] looks like
f y1 (f y2 (... (f yk x) ...))
whereas the recursion for foldl f x ys looks like
f (... (f (f x y1) y2) ...) yk
An important difference here is that if the result of f x y can be computed using only...
比尔盖茨“未来生活预言”的科技豪宅（图） - 资讯 - 清泛网 - 专注C/C++及内核技术
...，他家就指引着数字生活的航向。
豪宅名叫“世外桃源2.0”，位于美国西雅图的华盛顿湖畔，从市区开车只需25分钟。“世外桃源2.0”这个名字来源于《CitizenKane》里 CharlesFosterKane虚构的房屋。
盖茨把岸边小山挖去一半，前临...
Acronyms in CamelCase [closed]
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206
Some guidelines Microsoft has written about camelCase are:
When using acronyms, use Pascal...
How to programmatically round corners and set random background colors
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213
Instead of setBackgroundColor, retrieve the background drawable and set its color:
v.setBackg...
Finding duplicates in O(n) time and O(1) space
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edited Nov 25 '15 at 9:44
answered Apr 21 '11 at 3:54
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Check if directory mounted with bash
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answered Feb 23 '12 at 23:12
Christopher NeylanChristopher Neylan
7,17933 gold badges3232 silver badges4848 bronze badges
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Hash collision in git
...aracter times 40... 160 bits. Now we know 10 bits is approximately 1000 (1024 to be exact) meaning that there are 1 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 different SHA-1 hashes... 1048.
What is this equivalent of? Well the Moon is made up of about 1047 atoms. So if we have ...
How do I disable the “Press ENTER or type command to continue” prompt in Vim?
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answered May 20 '09 at 23:55
TabithaTabitha
2,30611 gold badge2020 silver badges2121 bronze badges
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Adding up BigDecimals using Streams
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3.1. We supply an identity value for addition, namely BigDecimal.ZERO.
3.2. We specify the BinaryOperator<BigDecimal>, which adds two BigDecimal's, via a method reference BigDecimal::add.
Updated answer, after edit
I see that you have added new data, therefore the new answer will become:
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Create unique constraint with null columns
..., menu_id, recipe_id)
WHERE menu_id IS NOT NULL;
CREATE UNIQUE INDEX favo_2col_uni_idx ON favorites (user_id, recipe_id)
WHERE menu_id IS NULL;
This way, there can only be one combination of (user_id, recipe_id) where menu_id IS NULL, effectively implementing the desired constraint.
Possible dra...