Add simple conditional processing and file include

Can now use C-style include declarations to include files within other sail files. This is done in such a way that all the location information is preserved in error messages. As an example:

$include "aarch64/prelude.sail"
$define SYM
$ifndef SYM
$include <../util.sail>
$endif

would include the file aarch64/prelude.sail relative to the file where the include is contained. It then defines a symbol SYM and includes another file if it is not defined. The <../util.sail> include will be accessed relative to $SAIL_DIR/lib, so $SAIL_DIR/lib/../util.sail in this case.

This can be used with the standard C trick of

$ifndef ONCE
$define ONCE
val f : unit -> unit
$endif

so no matter how many sail files include the above file, the valspec for f will only appear once.

Currently we just have $include, $define, $ifdef and $ifndef (with $else and $endif). We're using $ rather than # because # is already used in internal identifiers, although this could be switched.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/parser.mly b/src/parser.mly
index b11b4b61..32ee3368 100644
--- a/src/parser.mly
+++ b/src/parser.mly
@@ -182,6 +182,8 @@ let rec desugar_rchain chain s e =
 %token <string> Op0l Op1l Op2l Op3l Op4l Op5l Op6l Op7l Op8l Op9l
 %token <string> Op0r Op1r Op2r Op3r Op4r Op5r Op6r Op7r Op8r Op9r
 
+%token <string * string> Pragma
+
 %token <Parse_ast.fixity_token> Fixity
 
 %start file
@@ -1246,6 +1248,8 @@ def:
     { DEF_default $1 }
   | Mutual Lcurly fun_def_list Rcurly
     { DEF_internal_mutrec $3 }
+  | Pragma
+    { DEF_pragma (fst $1, snd $1, loc $startpos $endpos) }
 
 defs_list:
   | def