How do I use 'plain' and 'pure'?

Question

Once I've been told that saying 'this code is pure C' is incorrect, and I should use 'plain' instead of 'pure'.

Unfortunately, I can't see any difference. For example, how do I say something like this:

• 'You cannot solve this problem using plain (?) algebra. You have to use some geometry as well'
• '@autoreleasepool is not plain (?) C, it's Objective-C.'

I know there are some set phrases like 'This [idea] is pure genius' and in this case one can't replace 'pure' with 'plain'.

What about other cases? When to use 'plain' and when to use 'pure'?

Answer 1

What did you mean what you said the program is "pure C"?

"Pure" means this and nothing else, no contaminants or extra ingredients. "Plain" means ordinary.

So if your point was that the program is written with C and C alone, that there is no Java or Visual Basic or COBOL code in there, than your statement was perfectly correct and the normal way to express this idea.

If you meant that it used traditional C, K&R-ish, and not C# or C++, then I'd say "pure C" is not the correct term. "Plain C" would be more accurate, as you mean the ordinary, old, traditional C, and not the fancy new kinds of C like C#.

Answer 2

Plain has the meaning without embellishment or bells and whistles or additional features
Pure has the meaning without other ingredients

this code is pure C

is correct if the codebase is only in C and nothing else

Plain C is usually as specified by Kernighan and Ritchie, other flavours of C will depend on the compiler implementation, for example how macros are handled or compile time variables or object handling.

Another example would be orange juice:

Plain orange juice can be thought of as the juice from sweet oranges and is the official orange juice of Florida. Fancier orange juices may use blood, valencia, or mandarin oranges as their source.

Pure 100% orange juice would be juice from only oranges without any additives and is sometimes referred to as fresh squeezed when appropriate. Orange juice additives may include calcium, omega-3, vitamin-D, anti-oxidants, as well as other fruit juices. A popular addition to orange juice is vodka and the result is called a screwdriver.

For your algebra example

plain algebra

may refer to what is more technically called elementary algebra also colloquially called simple algebra or high school algebra to make the distinction with

abstract algebra
polynomial algebra
linear algebra
non-linear algebra