[augeas-devel] augeas: master - Language: allow '_' as an identifier that is never bound

[David Lutterkort]

Gitweb:        http://git.fedorahosted.org/git/augeas.git?p=augeas.git;a=commitdiff;h=3c9c9da314aac8d422f80bc7be1655079064cbbc
Commit:        3c9c9da314aac8d422f80bc7be1655079064cbbc
Parent:        911e52f8f851e483dc03d8d75be7bed3ac667a75
Author:        David Lutterkort <lutter at redhat.com>
AuthorDate:    Fri Jan 15 16:51:14 2010 -0800
Committer:     David Lutterkort <lutter at redhat.com>
CommitterDate: Fri Jan 15 17:01:59 2010 -0800

Language: allow '_' as an identifier that is never bound

  The expression
    let _ = something
  will evaluate something and then immediately forget it

  * src/lexer.l (LID): allow leading underscore
  * src/syntax.c (bind, bind_type): do not bind '_'
---
 src/lexer.l  |    2 +-
 src/syntax.c |   16 +++++++++++++---
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/src/lexer.l b/src/lexer.l
index 66637e1..3e29d15 100644
--- a/src/lexer.l
+++ b/src/lexer.l
@@ -69,7 +69,7 @@ static char *regexp_literal(const char *s, int len) {
 
 DIGIT [0-9]
 UID    [A-Z][A-Za-z0-9_]*
-LID    [a-z][A-Za-z0-9_]*
+LID    [a-z_][A-Za-z0-9_]*
 LETREC   let[ \t]+rec
 WS     [ \t\n]
 QID    {UID}\.{LID}
diff --git a/src/syntax.c b/src/syntax.c
index 0e2f9b7..d4e3282 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -65,6 +65,9 @@ static const char *const type_names[] = {
     "transform", "function", NULL
 };
 
+/* The anonymous identifier which we will never bind */
+static const char const anon_ident[] = "_";
+
 static void print_value(FILE *out, struct value *v);
 
 /* The evaluation context with all loaded modules and the bindings for the
@@ -572,6 +575,9 @@ static struct type *ctx_lookup_type(struct info *info,
 static struct binding *bind_type(struct binding **bnds,
                                  const char *name, struct type *type) {
     struct binding *binding;
+
+    if (STREQ(name, anon_ident))
+        return NULL;
     make_ref(binding);
     make_ref(binding->ident);
     binding->ident->str = strdup(name);
@@ -601,11 +607,15 @@ static void unbind_param(struct binding **bnds, ATTRIBUTE_UNUSED struct param *p
     unref(b, binding);
 }
 
-/* Takes ownership of TYPE and VALUE */
+/* Takes ownership of VALUE */
 static void bind(struct binding **bnds,
                  const char *name, struct type *type, struct value *value) {
-    struct binding *b = bind_type(bnds, name, type);
-    b->value = ref(value);
+    struct binding *b = NULL;
+
+    if (STRNEQ(name, anon_ident)) {
+        b = bind_type(bnds, name, type);
+        b->value = ref(value);
+    }
 }
 
 /*