From 9d0f8a3fd2285f50ff2d8584c3f9352ca932e98a Mon Sep 17 00:00:00 2001
From: Regis Blanc <regwblanc@gmail.com>
Date: Fri, 20 Mar 2015 16:05:29 +0100
Subject: [PATCH] explaining basic imperative features
---
doc/xlang.rst | 34 +++++++++++++++++++++++++++++++---
1 file changed, 31 insertions(+), 3 deletions(-)
diff --git a/doc/xlang.rst b/doc/xlang.rst
index 760afbb22..d54462ed2 100644
--- a/doc/xlang.rst
+++ b/doc/xlang.rst
@@ -33,18 +33,46 @@ syntax.
The above example illustrates three new features introduced by XLang:
-1. Declaring a variable in a local scope
+1. Declaring a variable in a local scope
-2. Blocks of statement
+2. Blocks of expressions
3. Assignment
+You can use Scala variables with a few restrictions. The variables can only be
+declared and used locally in the same function, and inner functions cannot
+close over them. XLang introduces the possibility to use sequences of
+expressions (blocks) -- a feature not available in PureScala, where you're only
+option is a sequence of ``val`` which essentially introduce nested ``let``
+declarations.
+
+.. warning::
+ Be careful when combining variables with nested functions from PureScala. Leon
+ will reject code with nested functions accessing a variable from an outside scope:
+
+ .. code-block:: scala
+
+ def foo(x: Int) = {
+ var a = 12
+ def bar(y: Int): Int = {
+ a = a + 1
+ a + y
+ }
+ bar(17)
+ }
+
+ The problem with such code is the complications involved in representing closures as
+ they need a pointer to an environment containing the variables. Leon is only able
+ to handle closures with ``val``, where it is sufficient to explicitly pass the values
+ as parameters.
+
While loops
+***********
Arrays
+******
-Nested function closure on local variables.
.. note::
some note comes here
--
GitLab