Merge pull request JuliaLang#9516 from tlycken/master

Clarify scoping of if blocks

doc/manual/control-flow.rst

@@ -121,6 +121,39 @@ blocks as desired can be used. The condition expressions in the
 evaluates to ``true``, after which the associated block is evaluated,
 and no further condition expressions or blocks are evaluated.
 
+``if`` blocks are "leaky", i.e. they do not introduce a local scope. 
+This means that new variables defined inside the ``ìf`` clauses can 
+be used after the ``if`` block, even if they weren't defined before.
+So, we could have defined the ``test`` function above as
+
+.. doctest::
+
+ julia> function test(x,y)
+ if x < y
+ relation = "less than"
+ elseif x == y
+ relation = "equal to"
+ else 
+ relation = "greater than"
+ end
+ println("x is ", relation, " than y.")
+ end
+
+``if`` blocks also return a value, which may seem unintuitive to users
+coming from many other languages. This value is simply the return value
+of the last executed statement in the branch that was chosen, so
+
+.. doctest::
+
+ julia> x = 3
+
+ julia> if x > 0
+ "positive!"
+ else
+ "negative..."
+ end
+ "positive!"
+
 Note that very short conditional statements (one-liners) are frequently expressed using
 Short-Circuit Evaluation in Julia, as outlined in the next section.
 

doc/manual/variables-and-scoping.rst

@@ -30,7 +30,7 @@ The constructs introducing such blocks are:
 - ``type`` blocks.
 
 Notably missing from this list are
-:ref:`begin blocks <man-compound-expressions>`, which do
+:ref:`begin blocks <man-compound-expressions>` and :ref:`if blocks <man-conditional-evaluation>`, which do
 *not* introduce new scope blocks.
 
 Certain constructs introduce new variables into the current innermost