doc/style(9): relax boolean coercion rules even more

1 files changed, 16 insertions, 1 deletions

diff --git a/doc/style.9.txt b/doc/style.9.txt
index 30322f32..c61bc777 100644
--- a/doc/style.9.txt
+++ b/doc/style.9.txt
@@ -613,7 +613,9 @@ the macro used to declare an array again in the iteration code.
 Boolean Coercion
 ~~~~~~~~~~~~~~~~
 
-Boolean coercion is forbidden by default. It is only allowed when
+Boolean coercion should only be used when the resulting text is semantically
+valid, i.e. it can be understood that the expression is either true, or false.
+
 checking error codes and pointers. For example :
 
 [source,c]
@@ -622,6 +624,7 @@ int error;
 
 error = do_something();
 
+/* Valid */
 if (error) {
     if (error != ERROR_AGAIN) {
         printf("unexpected error\n");
@@ -629,6 +632,18 @@ if (error) {
 
     return error;
 }
+
+int color;
+
+color = get_color();
+
+/* Invalid */
+if (!color) {
+    print_black();
+} else if (color == 1) {
+    print_red();
+}
+
 --------------------------------------------------------------------------------
 
 There are historical uses of the *int* type for boolean values, but all of