diff --git a/docs/book/examples/tasks_weak2/wscript b/docs/book/examples/tasks_weak2/wscript
new file mode 100644
index 00000000..10e8ce56
--- /dev/null
+++ b/docs/book/examples/tasks_weak2/wscript
@@ -0,0 +1,46 @@
+#! /usr/bin/env python
+
+"""
+Illustrate the effect of weak order constraints for the build (generates diagrams)
+
+waf configure clean build -j2 --dwidth=800 --dtitle='Default constraints on "waf -j2"' --dmaxtime=15
+waf configure clean build -j2 --dwidth=800 --dtitle='Additional constraints on "waf -j2"' --dmaxtime=15
+"""
+
+def options(ctx):
+	ctx.load('parallel_debug')
+
+def configure(ctx):
+	ctx.load('parallel_debug')
+
+def build(ctx):
+	ctx(rule='sleep 1', color='BLUE', name='blue')
+	for x in range(80):
+		ctx(rule='sleep 0.1', color='GREEN', name='green', always=True)
+	ctx(rule='sleep 6', color='RED', name='red', after='blue')
+
+from waflib import Task, Runner
+
+old = Task.set_file_constraints
+def meth(lst):
+	lst.sort(cmp=lambda x, y: cmp(x.__class__.__name__, y.__class__.__name__))
+	old(lst)
+Task.set_file_constraints = meth
+
+def get_out(self):
+	tsk = self.prev_get_out()
+	if tsk.__class__.__name__ == 'blue':
+		reds = []
+		def remove_red(lst):
+			for tsk in reversed(lst):
+				if tsk.__class__.__name__ == 'red':
+					lst.remove(tsk)
+					reds.append(tsk)
+		remove_red(self.outstanding)
+		remove_red(self.frozen)
+		for x in reds:
+			self.outstanding.insert(0, x)
+	return tsk
+Runner.Parallel.prev_get_out = Runner.Parallel.get_out
+Runner.Parallel.get_out      = get_out
+