proper -- can this postpositive adjective be substituted for "in and of itself"?

Question

Example:

In computer programming, a directive pragma (from "pragmatic") is a language construct that specifies how a compiler (or assembler or interpreter) should process its input. Directives are not part of the language proper – they are not part of the grammar, and may vary from compiler to compiler – but instead function either as an in-band form of a command-line option, specifying compiler behavior, or are processed by a preprocessor.

Is it alright to understand the word proper when used as a postpositive adjective as the expression in and of itself?

Answer 1

Both of those phrases are used to distinguish between a core concept or object and other things that may be linked to it, but they are used to eliminate different things.

The expression "X proper" means "the true X" or "the core X". It is used to distinguish between an object and something else that is either very similar, or very closely linked to it.

For example, one might refer to London proper to mean the area that is officially designated as part of the city, as opposed to Greater London, which is the whole urban area that has built up around it.

Or, as Omnidisciplinarianist mentions: a wolf may not be a dog proper, but it still looks and acts a lot like one.

The expression "X in and of itself", on the other hand, means "X, without assistance from anything else". It is used to distinguish between something that is complete, and things that need something else added.

An engine is not a motorbike in and of itself, but it's still a very important part of one.

This nutrient paste is a complete diet in and of itself - you don't need to add anything else to stay healthy.

Answer 2

Short Answer:

No

Long Answer:

The expression in and of itself is defined by both the Cambridge Dictionary of American Idioms and Random House Dictionary to mean either intrinsically or considered alone. Neither of these definitions are "close" to the definition of proper in this context (which is, as CarSmack links and Aes states, in the strict[est] sense or in its true[st] form).

If it helps, the following two are common examples of where you'll see the phrase used:

1. Closely related to, and having a number of X-like qualities, but not actually an X
   A gray wolf may not be a dog [in the strictest sense of the word], but it still looks like and acts much like a Husky, which is.
2. In the process of becoming an X, especially if nearly complete
   A trained medical professional with a degree whom is currently undergoing a period of supervised practice isn't a doctor [in the truest sense of the word] in the United States of America until that period is completed successfully.

Answer 3

May be this could be helpful.

I've often corrected people around me, here in India. Let's take this conversation as an example.

Where do you live, Anand? ~ I live in Mumbai
Oh! Proper Mumbai? ~ No! Mumbai proper.

When placed before noun, it serves as an adjective meaning suitable for the purpose/reason or something real.

But when it's placed after noun, it means 'main' or something core.

Having said this,

Directives are not part of the language proper....

means directives aren't the core/main part of the language and thus, it varies from a compiler to compiler.