simplification for [[ functions in -e mode

fun_assign2.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+
+set -e
+
+do_something() [[ "$1" == "false" || -z "$1" ]]
+
+if x=$(do_something)
+then echo "1:succ:$x:$?"
+else echo "1:fail:$x:$?"
+fi
+
+if x=$(do_something false)
+then echo "2:succ:$x:$?"
+else echo "2:fail:$x:$?"
+fi
+
+if x=$(do_something true)
+then echo "3:succ:$x:$?"
+else echo "3:fail:$x:$?"
+fi