diff --git a/pkg/R/afind.R b/pkg/R/afind.R
index 5308453..68d6c58 100644
--- a/pkg/R/afind.R
+++ b/pkg/R/afind.R
@@ -31,7 +31,10 @@
 #' The functions \code{grab} and \code{grabl} are approximate string matching
 #' functions that mimic base R's \code{\link[base]{grep}} and
 #' \code{\link[base:grep]{grepl}}. They are implemented as convenience wrappers
-#' of \code{find}.
+#' of \code{find}. For \code{grabl} there is one difference with \code{grepl}.
+#' The result of \code{grepl("foo",NA)} is \code{FALSE}, which seems inconsistent
+#' with \code{grepl(NA, NA)} and \code{grepl(NA, "foo")} which return \code{NA}.
+#' \code{grabl} returns \code{NA} when either \code{pattern} or \code{x} is \code{NA}.
 #'
 #' @section Running cosine distance:
 #' This algorithm gains efficiency by using that two consecutive windows have
@@ -174,16 +177,16 @@ grab <- function(x, pattern, maxDist=Inf, value=FALSE, ...){
 grabl <- function(x, pattern, maxDist=Inf, ...){
   stopifnot(is.numeric(maxDist), maxDist >= 0, length(pattern) == 1)
   L <- afind(x, pattern, value=FALSE, ...)
-  L$distance <= maxDist
+  as.logical(L$distance <= maxDist)
 }
 
 
 #' @rdname afind
 #'
 #' @return
-#' For \code{extract}, a \code{character} vector of \code{length(x)}, with
-#' \code{NA} where no match was found and the first matched string if there is
-#' a match. (similar to \code{stringr::str_extract}).
+#' For \code{extract}, a \code{character} matrix with \code{length(x)} rows and
+#' \code{length(pattern)} columns.  If match was found, element \eqn{(i,j)}
+#' contains the match, otherwise it is set to \code{NA}.
 #' @export
 extract <- function(x, pattern, maxDist = Inf, ...){
   stopifnot(is.numeric(maxDist), maxDist >= 0, length(pattern) == 1)
diff --git a/pkg/inst/tinytest/test_afind.R b/pkg/inst/tinytest/test_afind.R
index ca327dc..d522515 100644
--- a/pkg/inst/tinytest/test_afind.R
+++ b/pkg/inst/tinytest/test_afind.R
@@ -51,10 +51,10 @@ expect_equal(length(out2), 2)
 expect_equal(grab(texts, "harvester", maxDist=2), 2)
 expect_equal(grab(texts, "harvester", value=TRUE, maxDist=2), "harverste")
 expect_equal(grabl(texts, "harvester", maxDist=2)
-            , matrix(c(FALSE,TRUE,FALSE,FALSE),nrow=4))
+            , c(FALSE,TRUE,FALSE,FALSE))
 
 expect_equal(extract(texts, "harvester", maxDist=2)
-            , matrix(c(NA, "harverste",NA,NA), nrow=4) )
+            , matrix(c(NA, "harverste",NA,NA),nrow=4) )
 
 ## Test running_cosine
 pattern <- c("phish", "want to")
@@ -76,7 +76,30 @@ for ( method in methods ){
   expect_equal(afind(text, pattern, method=method, q=3, p=0.1)$location[1,1], 19, info=method)
 }
 
+## test the usual edge cases
 
+# notice: window size = 0.
+expect_equal(afind("foo","")$distance[1], 0)
+
+expect_equal(afind("foo",NA)$distance[1], NA_real_)
+expect_equal(afind("foo",NA)$location[1], NA_integer_)
+expect_equal(afind("foo",NA)$match[1], NA_character_)
+
+expect_equal(afind(NA,"foo")$distance[1], NA_real_)
+expect_equal(afind(NA,"foo")$location[1], NA_integer_)
+expect_equal(afind(NA,"foo")$match[1], NA_character_)
+
+expect_equal(afind("","foo")$distance[1], 3)
+expect_equal(afind("","foo")$location[1], 1)
+expect_equal(afind("","foo")$match[1], "")
+
+expect_equal(grab("foo", ""), 1L)
+expect_equal(grabl("foo",""), TRUE)
+expect_equal(grab("foo",NA), integer(0))
+
+# note that 'grepl' gives FALSE in this case (which is inconsistent with
+# grepl(NA, NA), grepl(NA, "foo").
+expect_equal(grabl("foo",NA), NA)
 
 
 
diff --git a/pkg/src/Rstringdist.c b/pkg/src/Rstringdist.c
index fdcd4b9..f747e28 100644
--- a/pkg/src/Rstringdist.c
+++ b/pkg/src/Rstringdist.c
@@ -418,7 +418,7 @@ SEXP R_afind(SEXP a, SEXP pattern, SEXP width
         if (isna_s || isna_t){ // something to search in, or find?
           yloc[offset + i]  = NA_INTEGER;
           ydist[offset + i] = NA_REAL;
-        } else if ( current_window >= len_s ){ // is the text shorter than the pattern?
+        } else if ( current_window >= len_s ){ // is the text shorter than the window?
           yloc[offset + i]  = 1L;
           ydist[offset + i] = stringdist(sd, s, len_s, t, len_t); 
         } else { // slide window over text and compute distances
diff --git a/pkg/src/qgram.c b/pkg/src/qgram.c
index 24fe77a..b93c2bc 100644
--- a/pkg/src/qgram.c
+++ b/pkg/src/qgram.c
@@ -456,7 +456,7 @@ double running_cosine_dist(
   double *store
   ){
   
-  double d, ww, wp, pp;
+  double d;
 
   unsigned int *first_qgram;
   unsigned int *last_qgram;