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+# Chapter 25: Modules
+
+
+You can also read [this chapter](https://github.com/SeaOfNodes/Simple/tree/linear-chapter25) in a linear Git revision history on the [linear](https://github.com/SeaOfNodes/Simple/tree/linear) branch and [compare](https://github.com/SeaOfNodes/Simple/compare/linear-chapter22...linear-chapter24) it to the previous chapter.
+
+
+## Modules
+
+Goal: A Module plan (not yet a "system")
+Goal: No syntax for the starter 1-file-1-line helloWorld.smp "module"
+Goal: External symbols are in ".o" files, like Java ".class" - not an source file #include like C/C++
+
+Needs a search strategy for ".o" files, so they mirror the source code directory structure.
+Means there is a "build" root for .o files.
+Means the CLI has a --flag for the build root, or some sensible default ($cwd/build)
+
+Projects with subdirectories pick up all symbols qualified names from the path-to-project-root
+
+Goal: under no circumstances can you load from an uninitialized variable  (although you can see default inits for fields that have defaults).
+Goal: nested tree-structured name spaces, to control complexity.
+Goal: field decl order within a file is fairly flexible.
+
+
+## more
+
+Has a defined project root (default: CWD).
+
+Has a path to root: %PATH, e.g. $ROOT/a/b/c/
+
+Has a file name: $ROOT/ a/b/c/  foo.smp
+
+Everything in a dir is implicitly in name-space above it.
+
+Suppose `foo.smp` contains `PI=3.14;`
+
+Then the fully qualified name is: a.b.c.foo.PI
+
+Code is implicitly in the `struct a.b.c.foo {}` namespace.
+
+Final constant values can be accessed by direct names.
+
+Non-finals or non-constant need a constructed object.
+
+
+
+Top-level code in `foo.smp` is implicitly in the foo class init,
+which runs the first time foo is touched,
+which requires a "has been init" touch on every possible-first-access,
+which is every non-local ("sideways") reference.
+
+Always the init for parents are done before children,
+so `a` completes before `a.b`, and so on.
+
+Means `a` init can NOT reference e.g. `b,c,foo`, although
+you can define top-level fcns that refer to `b`.
+
+Legal in `a.smp`:  `val make_b = { -> new b{} };` // fcn is final constant
+
+Legal in `a.smp`:  `val      b =      new b{}  ;` // not constant, so requires instance & <clinit> is done
+
+Means making an `a` instance in a's <clinit>, will also run a's <init>
+which can refer to instance fcns, which can refer to not-init finals?
+Limit: all fcns can only refer to instance vars *before* them.
+
+
+
+Would like to make golden instances, static singletons:
+val special = new a{/*anything already in-scope and <clinit>ed*/};
+
+
+
+The default 1-file main then:
+$ROOT==$CWD
+Code is implicitly in the *empty* name space, is in the <clinit> for the empty
+name space and gets run on project start.
+
+------
+
+Implications for e.g. sys:
+
+    .../simple/sys.smp - top level, has sys.parseAryI64
+     ../simple/sys/sys.io.smp - has `struct io { ... }`
+
+
+For now just gather the exported TYPE symbols, and a count of them, and export/input ELF.
+NO: for now split into `sys` class from instance, 
+\ No newline at end of file