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Many-to-many relationship with the same model in rails?
...schema for your posts:
create_table "posts", :force => true do |t|
t.string "name", :null => false
end
For any many-to-many relationship, you need a join table. Here's the schema for that:
create_table "post_connections", :force => true, :id => false do |t|
t.integer "post_a_id"...
In Python, how do I split a string and keep the separators?
...e: Well, it's documented: docs.python.org/library/re.html#re.split: "Split string by the occurrences of pattern. If capturing parentheses are used in pattern, then the text of all groups in the pattern are also returned as part of the resulting list."
– Vinay Sajip
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In Rails, how do you render JSON using a view?
...le quotes to double quotes, as JSON (unlike JS) only accepts double-quoted strings.
– Abe Voelker
Jan 20 '12 at 20:27
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Is the sizeof(some pointer) always equal to four?
For example:
sizeof(char*) returns 4. As does int* , long long* , everything that I've tried. Are there any exceptions to this?
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Repeat Character N Times
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These days, the repeat string method is implemented almost everywhere. (It is not in Internet Explorer.) So unless you need to support older browsers, you can simply write:
"a".repeat(10)
Before repeat, we used this hack:
Array(11).join("a") //...
Inheriting from a template class in c++
... create objects from any other class). Another such class would be Area<char>. Note that those are completely different classes, which have nothing in common except for the fact that they were generated from the same class template.
Since Area is not a class, you cannot derive the class Recta...
PHP: Convert any string to UTF-8 without knowing the original character set, or at least try
...t mb_detect_encoding source code in your php distro (somewhere here: ext/mbstring/libmbfl/mbfl/mbfl_ident.c). This function does not work properly at all. For some encodings it even has "return true", lol. Others are in Ctrl+c Ctrl+v functions. That's because you can not detect encoding without some...
How can you zip or unzip from the script using ONLY Windows' built-in capabilities?
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It was possible back in 2013 (without installing any extra software). See the Super User question. It has been possible since Windows XP came out in 2001. The built-in ZIP functionality in Windows XP can be leveraged because it is exposed through a COM interface.
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When should I use perror(“…”) and fprintf(stderr, “…”)?
... to perror(NULL) since a call to strerror(errno) will generate the printed string value for errno, and you can then combined that with any other custom error message via fprintf.
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Reasons for using the set.seed function
...set the seed (or choose a seed to pass into set.seed) based on a character string. For example you could have students use their name as the seed then each student has a unique dataset but the instructor can also create the same datasets for grading.
– Greg Snow
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