CODEWITHSUNDEEP
schemechicken-scheme
beroal
beroal

Reputation: 397

What is a library unit in Chicken Scheme?

The terms "unit" and "library unit" are used in many places on the web site, but I failed to find documentation or even definitions of these terms. The only description that I found is in "User's Manual/Supported language/Declarations/(unit|uses)". Also there is an example in "User's Manual/Using the compiler/An example with multiple files". As you can see, very scarce.

If I ever get a response, the next question is how are "units" related to modules described in "User's Manual/Supported language/Modules"? I suppose that "units" somehow relate to compilation, while modules relate to Scheme value names.

Upvotes: 2

Views: 331

Answers (1)

sjamaan
sjamaan

Reputation: 2292

Unit is short for "unit of compilation", which is basically a compiled library. If you look at the source code for CHICKEN, you'll notice that each unit from the manual corresponds (roughly) to a source file. Each source file is compiled separately into a .o file, and these units are all linked together into libchicken.so/libchicken.a.

This terminology is not very relevant anymore, except when you're linking statically. Then you need (declare (uses ...)), which refers to the unit name. This is needed, because the toplevel of the particular unit needs to run before the toplevels that depend upon it, so that any definitions are loaded.

In modern code you'll typically use only modules, but that means your code won't be statically linkable. We know this is confusing, which is why we're attempting to make static linking with modules easier with CHICKEN 5, and reducing the need to know about units.

Upvotes: 3

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