added sigmoid - a simple example of back-chained math

diff --git a/examples/sigmoid.dyna b/examples/sigmoid.dyna
new file mode 100644 (file)
index 0000000..c095838
--- /dev/null
+++ b/examples/sigmoid.dyna
@@ -0,0 +1,6 @@
+% FIXME: should all be '=' instead of '+='
+sigmoid(X) += 1 / (1 + exp(-X)).
+
+a += sigmoid(-1).
+b += sigmoid(0).
+c += sigmoid(1).
\ No newline at end of file