From 3cb552371037dee8e75ef1b05e39e7b3c9ed5f92 Mon Sep 17 00:00:00 2001
From: Edwin Brady <eb@cs.st-andrews.ac.uk>
Date: Thu, 13 Jan 2011 14:46:06 +0000
Subject: [PATCH] Add malloc_ to Epic interface

---
 Epic/Epic.lhs                  | 10 ++++++++++
 Papers/Epic/implementation.tex | 16 ++++++++++++++++
 2 files changed, 26 insertions(+)
 create mode 100644 Papers/Epic/implementation.tex

diff --git a/Epic/Epic.lhs b/Epic/Epic.lhs
index 15a8e73..e377981 100644
--- a/Epic/Epic.lhs
+++ b/Epic/Epic.lhs
@@ -21,6 +21,7 @@
 >                  foreign_, foreignL_, foreignConst_, foreignConstL_,
 >                  let_, letN_, update_, op_,
 >                  str, int, float, char, bool, unit_, (!.), fn, ref, (+>),
+>                  malloc_,
 >                  -- * Types
 >                  Type, tyInt, tyChar, tyBool, tyFloat, tyString,
 >                  tyPtr, tyUnit, tyAny, tyC,
@@ -262,6 +263,15 @@ Remaining expression constructs
 > foreignConst_ t str = term $ ForeignCall t str []
 > foreignConstL_ t str = term $ LazyForeignCall t str []
 
+> -- | Evaluate an expression under manually allocated memory. Creates a pool
+> -- of memory. All allocation is from this pool, and there is no garbage
+> -- collection. The pool is freed after evaluation.
+> malloc_ :: (EpicExpr a, EpicExpr b) => 
+>               a -- ^ Size of block to allocate
+>            -> b -- ^ Expression to evaluate
+>            -> Term
+> malloc_ = exp2 (WithMem FixedPool)
+
  mkCon :: Int -> [Term] -> Term
  mkCon tag args = do args' <- mapM expr args
                      return (Con tag args')
diff --git a/Papers/Epic/implementation.tex b/Papers/Epic/implementation.tex
new file mode 100644
index 0000000..c857c4d
--- /dev/null
+++ b/Papers/Epic/implementation.tex
@@ -0,0 +1,16 @@
+\section{Implementation}
+
+How it's implemented is not really important to the user --- a
+compiler can target Epic without knowing, and we could drop in a new
+back end at any time in principle.
+
+There is currently one back end, but more are planned. Compiled via
+C. Garbage collection with Boehm~\cite{boehm-gc},
+\texttt{\%memory}. (Note that a non-moving collector makes things
+easier for foreign functions, but may not be the best choice in the
+long run).
+
+Later plans: compile via LLVM, allow plug in garbage collectors
+(important for embedded systems, device drivers, operating system
+services, for example).
+