Changes between Version 38 and Version 39 of Sysel

Timestamp:

2011-03-06T21:38:15Z (15 years ago)

Author:

Jiri Svoboda

Comment:

Some SBI internals

Sysel

@@ -61 +61 @@
  * All errors should be handled gracefully. Calls to `exit()` must be eliminated.
 
+=== How SBI works ===
+
+SBI first takes all the code in the ''library'' and all the source files provided on the command-line and pre-processes them in several stages:
+
+|| Parsing             || Lex and parse source files to produce a syntax tree ||
+|| Ancestry resolution || Determine ancestry of classes and interfaces ||
+|| Typing              || Annotate syntax tree with static types and make all type conversions explicit ||
+
+The result is a syntax tree with symbol references resolved, annotated with static types and augmented
+so that type all conversions are explicit. This syntax tree is considered the ''program'', it is
+treated as read-only for the purpose of execution.
+
+SBI has a concept of a ''runner object'' (`run_t`) which is sort of similar to a process. It has a reference to the code
+that should be executed, to global/shared state (i.e. the heap) and to the thread(s). (There is only one thread
+currently, anyway.) A thread has its own private state consisting of a stack (of procedure
+activation records) and error/exception state.
+
+Data is managed using a system of interlinked structures -- `rdata` nodes. `rdata_var` nodes are used to implement
+both ''variables'' (addressable memory nodes that can be read and written) and ''values''. Values are immutable.
+so they can be copied just by copying the pointer to them. Values can be written to or read from variables.
+
+The equivalent of a data pointer in the `rdata` system is an ''address''. An address can refer both to a variable
+or a to property. Reading from or writing to a property (using its address) causes its getter or setter to be invoked.
+The equivalent of a code pointer is a delegate (this is not the same delegate as the language construct), which
+refers to a symbol and, optionally, to an object instance on which the symbol should be invoked.
+
+To implement L-values and R-values, an ''item'' is the result of evaluating an expression. An item can be either
+an ''address item'' (L-value) or a ''value item'' (R-value).
+
 == NNPS ==