Data commit

Task/Variables/Tcl/variables.tcl

@@ -0,0 +1,23 @@
+namespace eval foo {
+    # Define a procedure with two formal arguments; they are local variables
+    proc bar {callerVarName argumentVar} {
+        ### Associate some non-local variables with the procedure
+        global globalVar;      # Variable in global namespace
+        variable namespaceVar; # Variable in local (::foo) namespace
+        # Access to variable in caller's context; may be local or global
+        upvar 1 callerVarName callerVar
+
+        ### Reading a variable uses the same syntax in all cases
+        puts "caller's var has $callerVar"
+        # But global and namespace vars can be accessed by using qualified names
+        puts "global var has $globalVar which is $::globalVar"
+
+        ### Writing a variable has no special syntax
+        ### but [set] is by far the most common command for writing
+        set namespaceVar $globalVar
+        incr globalVar
+
+        ### Destroying a variable is done like this
+        unset argumentVar
+    }
+}