Dot-prefix local vars when we never want to use similarly-named arg

Local variables `f`, `starts`, and `stops` are never used at the same time as
arguments `.f`, `.starts`, and `.stops`. To prevent accidental usage due to
similar naming, dot-prefix the local variables as well. We might later separate
out helper functions from being nested functions, and this would avoid such
accidents as well; we then may be able to remove some of these dot prefixes if
desired.

Author: brookslogan

R/slide.R

@@ -191,8 +191,8 @@ epi_slide <- function(
   .x <- arrange(.x, .data$time_value)
 
   # Now set up starts and stops for sliding/hopping
-  starts <- .ref_time_values - before
-  stops <- .ref_time_values + after
+  .starts <- .ref_time_values - before
+  .stops <- .ref_time_values + after
 
   # If `.f` is missing, interpret ... as an expression for tidy evaluation
   if (missing(.f)) {
@@ -211,7 +211,7 @@ epi_slide <- function(
     used_data_masking <- FALSE
   }
 
-  f <- as_time_slide_computation(.f, ...)
+  .f <- as_time_slide_computation(.f, ...)
 
   # Create a wrapper that calculates and passes `.ref_time_value` to the
   # computation. `i` is contained in the `f_wrapper_factory` environment such
@@ -222,7 +222,7 @@ epi_slide <- function(
     f_wrapper <- function(.x, .group_key, ...) {
       .ref_time_value <- kept_ref_time_values[[i]]
       i <<- i + 1L
-      f(.x, .group_key, .ref_time_value, ...)
+      .f(.x, .group_key, .ref_time_value, ...)
     }
     return(f_wrapper)
   }
@@ -246,15 +246,15 @@ epi_slide <- function(
     .stops <- .stops[o]
     kept_ref_time_values <- .ref_time_values[o]
 
-    f <- .f_factory(kept_ref_time_values)
+    .f <- .f_factory(kept_ref_time_values)
 
     # Compute the slide values
     slide_values_list <- slider::hop_index(
       .x = .data_group,
       .i = .data_group$time_value,
       .starts = .starts,
       .stops = .stops,
-      .f = f,
+      .f = .f,
       .group_key, ...
     )
 
@@ -339,8 +339,8 @@ epi_slide <- function(
   .x <- group_modify(.x, slide_one_grp,
     ...,
     .f_factory = f_wrapper_factory,
-    .starts = starts,
-    .stops = stops,
+    .starts = .starts,
+    .stops = .stops,
     .ref_time_values = .ref_time_values,
     .all_rows = .all_rows,
     .new_col_name = .new_col_name,