Parse decimal values

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/frontends/lean/lean_parser.cpp

@@ -884,10 +884,14 @@ class parser::imp {
     }
 
     expr parse_decimal() {
-        not_implemented_yet();
+        auto p = pos();
+        expr r = save(mk_real_value(m_scanner.get_num_val()), p);
+        next();
+        return r;
     }
 
     expr parse_string() {
+        // TODO
         not_implemented_yet();
     }
 

tests/lean/arith8.lean

@@ -0,0 +1,5 @@
+Eval 10.3
+Eval 0.3
+Eval 0.3 + 0.1
+Eval 0.2 + 0.7
+Eval 1/3 + 0.1

tests/lean/arith8.lean.expected.out

@@ -0,0 +1,7 @@
+  Set: pp::colors
+  Set: pp::unicode
+103/10
+3/10
+2/5
+9/10
+13/30