Implement Hello World compilation support

Example programs which can be compiled can be found in the doc/example
folder.

A contemporary version of libbsa is required for this program (bscc)
to succeed at compilation, as well as to run the compiled Hello World
application.

Important short term TODOs are improved validation, and a test suite.

Author: iainnicol

.gitignore

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+# Copyright © 2012 Iain Nicol
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Build system generated.
+dist/
+*.hi
+*.o
+
+# Outputted by bscc, or required by its output
+*.exe
+# Nor do we output dlls, but libbsa is a DLL
+libbsa*.dll

AUTHORS

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+Iain Nicol

Bscc/Ast/Plain.ag

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+-- -*- auto-fill-mode: nil; indent-tabs-mode: nil; -*-
+
+PRAGMA datarecords
+PRAGMA genlinepragmas
+
+optpragmas
+{
+-- Copyright © 2012 Iain Nicol
+
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero General Public License as published by
+-- the Free Software Foundation, either version 3 of the License, or
+-- (at your option) any later version.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+-- (Just below is the module-level documentation.  However, we cannot
+-- make it a Haddock comment because that would cause compile failures
+-- when we are INCLUDEd from another .ag file with its own doc comment.)
+
+-- A plain Abstract syntax tree, such as a parse result.
+-- cf. "Bscc.Ast.WithSem".
+--
+-- Most of the AST datatypes should hopefully be self explanatory.
+}
+
+MODULE {Bscc.Ast.Plain}
+-- Exports
+{
+
+Project (..),                  -- $Project
+Modules, Module (..),          -- $Module
+Procs, Proc (..),              -- $Proc
+ArgDefs, ArgDef (..),          -- $ArgDef
+Type (..),                     -- $Type
+InProcStmts, InProcStmt (..),  -- $InProcStmt
+Exprs, Expr (..)               -- $Expr
+}
+-- Imports
+{
+import Bscc.Symbol.Name
+}
+
+
+DERIVING *: Show
+
+{
+-- $Project
+-- A project is a collection of source files which compile into a single
+-- executable.  For each program to be compiled, this is the type of
+-- the root node.
+}
+DATA Project
+   | Project  modules: Modules  name: SymbolName
+
+TYPE Modules = [Module]
+
+{
+-- $Module
+-- A module, or a (parsed) source file.
+--
+-- `BasModule': a \".bas\" file module.
+}
+DATA Module
+   | BasModule  path: FilePath  procs: Procs
+
+TYPE Procs = [Proc]
+
+{
+-- $Proc
+-- A procedure.
+--
+-- `Sub': A Sub has no return type.
+}
+-- We refuse to derive Eq for Proc here; two procedures can have the
+-- same name and yet be different procedures in different modules.
+DATA Proc
+   | Sub  name: SymbolName  argDefs: ArgDefs  body: InProcStmts
+
+TYPE ArgDefs = [ArgDef]
+
+{
+-- $ArgDef
+-- Defines an argument accepted by a `Proc'.
+}
+DATA ArgDef
+   | ArgDef  name: SymbolName  ty: Type
+
+{
+-- $Type
+-- Represents a data type.  Remember, the type represented is a BASIC
+-- type, not a Haskell type.
+}
+DATA Type
+   | String
+
+TYPE InProcStmts = [InProcStmt]
+
+{
+-- $InProcStmt
+-- A statement inside a `Proc'.
+
+-- `Call': a Call statement
+}
+DATA InProcStmt
+   | Call  fn: SymbolName  args: Exprs
+
+TYPE Exprs = [Expr]
+
+{
+-- $Expr
+-- An expression.
+}
+DATA Expr
+   | StringLit  val: String

Bscc/Ast/WithSem.ag

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+-- -*- auto-fill-mode: nil; indent-tabs-mode: nil; -*-
+
+PRAGMA datarecords
+PRAGMA genlinepragmas
+
+optpragmas
+{
+-- Copyright © 2012 Iain Nicol
+
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero General Public License as published by
+-- the Free Software Foundation, either version 3 of the License, or
+-- (at your option) any later version.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+-- (Just below is the module-level documentation.  However, we cannot
+-- make it a Haddock comment because that would cause compile failures
+-- when we are INCLUDEd from another .ag file with its own doc comment.)
+
+-- Abstract syntax tree with information from semantic analysis
+-- ("Bscc.Sem"), such as type information.
+--
+-- Most data types and constructors here correspond to those in
+-- "Bscc.Ast.Plain", except that this module prefixes such with \"S\"
+-- for \"Semantics\".
+}
+
+MODULE {Bscc.Ast.WithSem}
+-- Exports
+{
+SProject (..),
+SModules, SModule (..),
+SProcs, SProc (..),
+SProcPrototype (..),       -- $SProcPrototype
+SArgDefs, SArgDef (..),
+SType (..),
+SProcRetType,              -- $SProcRetType
+SInProcStmts, SInProcStmt (..),
+SExprs, SExpr (..)
+}
+-- Imports
+{
+import Bscc.Symbol.Name (SymbolName)
+}
+
+
+DERIVING *: Show
+
+DATA SProject
+   | SProject  modules: SModules  name: SymbolName
+
+TYPE SModules = [SModule]
+
+DATA SModule
+   | SBasModule  path: FilePath  procs: SProcs  name: SymbolName
+
+TYPE SProcs = [SProc]
+
+DATA SProc
+   | SProc  proto: SProcPrototype  body: SInProcStmts
+
+{
+-- $SProcPrototype
+-- Although the language we compile has no prototypes for functions or
+-- other procedures, pretend that it does.  Essentially, this structure
+-- contains the non-body information about a procedure.
+}
+DATA SProcPrototype
+   | SProcPrototype  name: SymbolName  argDefs: SArgDefs  retType: SProcRetType
+                     -- Project and Module where the implementation of
+                     -- the procedure resides.
+                     implProject: SymbolName  implModule: SymbolName
+
+-- This lets use {Data.Set.Set SProcPrototype}.
+DERIVING SProcPrototype SArgDefs SArgDef SType: Eq, Ord
+
+TYPE SArgDefs = [SArgDef]
+
+DATA SArgDef
+   | SArgDef  name: SymbolName  ty: SType
+
+DATA SType
+   | SString
+
+{
+-- $SProcRetType
+-- Return type of a procedure.  A `Bscc.Ast.Plain.Sub' has `Nothing'; a
+-- Function would have the the appropriate @`Just' foo@.
+}
+TYPE SProcRetType = MAYBE SType
+
+TYPE SInProcStmts = [SInProcStmt]
+
+DATA SInProcStmt
+   | SCall  proc: SProcPrototype  args: SExprs
+
+TYPE SExprs = [SExpr]
+
+DATA SExpr
+   | SStringLit  val: String  ty: SType