Author: pmichaud Date: Tue Oct 16 13:25:45 2007 New Revision: 22139 Modified: trunk/docs/pdds/draft/pdd26_ast.pod
Log: [docs]: * Finish up this draft of pdd26_ast.pod. Modified: trunk/docs/pdds/draft/pdd26_ast.pod ============================================================================== --- trunk/docs/pdds/draft/pdd26_ast.pod (original) +++ trunk/docs/pdds/draft/pdd26_ast.pod Tue Oct 16 13:25:45 2007 @@ -180,6 +180,11 @@ =back +If C<scope> is not explicitly provided in the node, then PAST will +look at the local symbol tables of any outer C<PAST::Block> nodes +to try to determine the scope of the named variable. If this still +does not result in a scope, then 'lexical' is assumed. + =item viviself([value]) Accessor method for the C<viviself> attribute, which specifies @@ -405,11 +410,81 @@ =head2 PAST::Block -Coming soon. +C<PAST::Block> nodes represent lexical scopes within an abstract +syntax tree, and roughly translate to individual Parrot subroutines. +A C<PAST::Block> node nested within another C<PAST::Block> node +acts like a nested lexical scope. + +If the block has a C<name> attribute, that becomes the name of +the resulting Parrot sub. Otherwise, a unique name is automatically +generated for the block. + +Each PAST::Block node can maintain its own local symbol table, see +the C<symbol> method below. + +=over 4 + +=item blocktype([type]) + +Get/set the type of the block to C<type>. The currently +understood values are 'declaration' and 'immediate'. 'Declaration' +indicates that a block is simply being defined at this point, the +result of the node is a reference to the block. A C<blocktype> +of 'immediate' indicates a block that is to be immediately +executed when it is evaluated in the AST, and the result of the +last operation is used as the return value for the block. + +=item namespace([value]) + +Get/set the namespace for this particular block (and any nested +blocks that do not explicitly provide a namespace). C<Value> +may either be a simple string or an array of strings representing +a nested namespace. + +=item symbol(name, [attr1 => val1, attr2 => val2, ...]) + +Each PAST::Block node can use the C<symbol> method to maintain +its own compile-time notion of a local symbol table. Each value +of C<name> is given its own hash to hold information about that +symbol for the block (i.e., the symbol table acts like a hash of +hashes indexed by symbol name). If the C<symbol> method is called +with named arguments, then the method sets the entries in the hash +corresponding to C<name> in the block's symbol table. If C<symbol> +is called with just a single C<name> argument, then the current hash +for local symbol C<name> is returned. + +HLLs are free to place any values in the symbol hashes that +may be useful. However, the C<scope> entry for a symbol is +typically used to provide the C<scope> attribute for any nested +C<PAST::Var> nodes that do not provide an explicit C<scope> attribute. + +=item pir_pragma([value]) + +Get/set any PIR pragmas to be used when generating the block. + +=item compiler([compiler_name]) + +Specify that the children nodes of this block are to be compiled +using C<compiler_name> instead of being treated as standard PAST +nodes. This is useful when a program may contain components of +code written in other HLLs. For example, the C<perl6> compiler +uses this feature to use PGE to compile pre-parsed Perl 6 regular +expressions, rather than trying to represent the semantics of +those expressions in PAST itself. + +When code is generated from a C<PAST::Block> node having a +C<compiler> attribute, the compiler is invoked with C<name> +and C<outer> arguments so that any generated subs can have +names and lexical scoping appropriate to the block (it's the +responsibility of the external compiler to support this). + +=back =head2 PAST::CompUnit -Coming soon. +C<PAST::CompUnit> nodes are used for the abstract representation +of compilation units. Specific attributes and semantics are +yet to be determined. =head1 COPYRIGHT @@ -422,4 +497,3 @@ # fill-column: 100 # End: # vim: expandtab shiftwidth=4: -
