Ensure ranks match in apply_broadcast

ERROR_IF to make sure rank(index) == rank(out_shape)
Also try to better explain what the expected value for index is.

Change-Id: I0731324d33335cb1ffc0a6fbd153fbc8521ce2e9
Signed-off-by: Eric Kunze <eric.kunze@arm.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/chapters/introduction.adoc b/chapters/introduction.adoc
index 3fb5476..51d085d 100644
--- a/chapters/introduction.adoc
+++ b/chapters/introduction.adoc
@@ -304,8 +304,13 @@ The following function maps an index in the output tensor to an index in the inp
 
 [source,c++]
 ----
+// The index argument should be a valid location within out_shape.
+// The function returns the location within in_shape that contributes
+// to the output based on broadcasting rules.
+
 dim_t apply_broadcast(dim_t out_shape, dim_t in_shape, dim_t index) {
     ERROR_IF(rank(out_shape) != rank(in_shape));
+    ERROR_IF(rank(out_shape) != rank(index));
     for (i = 0; i < rank(out_shape); i++) {
         if (out_shape[i] != in_shape[i]) {
             ERROR_IF(in_shape[i] != 1);