From 67382c15f7e9176dea44c3da7f7013759c88ce33 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 21 Jan 2016 15:03:26 +0200
Subject: Add support for ==, != in eval context

---
 build2/lexer.cxx | 54 +++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 43 insertions(+), 11 deletions(-)

(limited to 'build2/lexer.cxx')

diff --git a/build2/lexer.cxx b/build2/lexer.cxx
index 65bb5e9..da3d64e 100644
--- a/build2/lexer.cxx
+++ b/build2/lexer.cxx
@@ -126,8 +126,8 @@ namespace build2
 
     uint64_t ln (c.line), cn (c.column);
 
-    // This mode is quite a bit like the value mode when it comes
-    // to special characters.
+    // This mode is quite a bit like the value mode when it comes to special
+    // characters, except that we have some of our own.
     //
     switch (c)
     {
@@ -143,6 +143,15 @@ namespace build2
         mode_.pop (); // Expire eval mode.
         return token (type::rparen, sep, ln, cn);
       }
+    case '=':
+    case '!':
+      {
+        if (peek () == '=')
+        {
+          get ();
+          return token (c == '=' ? type::equal : type::not_equal, sep, ln, cn);
+        }
+      }
     }
 
     // Otherwise it is a name.
@@ -194,31 +203,34 @@ namespace build2
       if (m == lexer_mode::pairs && c == pair_separator_)
         break;
 
-      // The following characters are not treated as special in the
-      // value/pairs, eval, and quoted modes.
+      // The following characters are only special in the normal and
+      // variable name modes.
       //
-      if (m != lexer_mode::value &&
-          m != lexer_mode::pairs &&
-          m != lexer_mode::eval  &&
-          m != lexer_mode::quoted)
+      if (m == lexer_mode::normal || m == lexer_mode::variable)
       {
         switch (c)
         {
         case ':':
-        case '+':
         case '=':
           {
             done = true;
             break;
           }
+        case '+':
+          {
+            get ();
+            done = (peek () == '=');
+            unget (c);
+            break;
+          }
         }
 
         if (done)
           break;
       }
 
-      // While these extra characters are treated as the name end in
-      // the variable mode.
+      // These extra characters are treated as the name end in the variable
+      // mode.
       //
       if (m == lexer_mode::variable)
       {
@@ -236,6 +248,26 @@ namespace build2
           break;
       }
 
+      // These extra characters are treated as the name end in the eval mode.
+      //
+      if (m == lexer_mode::eval)
+      {
+        switch (c)
+        {
+        case '=':
+        case '!':
+          {
+            get ();
+            done = (peek () == '=');
+            unget (c);
+            break;
+          }
+        }
+
+        if (done)
+          break;
+      }
+
       // If we are quoted, these are ordinary characters.
       //
       if (m != lexer_mode::quoted)
-- 
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