From a20e956f6ddd37f3cdef07b241454015e113b572 Mon Sep 17 00:00:00 2001
From: Andrew Chambers <ac@acha.ninja>
Date: Tue, 3 Dec 2019 22:05:43 +1300
Subject: [PATCH] Explain the logic behind negative slice indices.
---
src/core/array.c | 3 ++-
src/core/string.c | 3 ++-
src/core/tuple.c | 5 ++++-
3 files changed, 8 insertions(+), 3 deletions(-)
diff --git a/src/core/array.c b/src/core/array.c
index 1eb67061..2e2a6692 100644
--- a/src/core/array.c
+++ b/src/core/array.c
@@ -273,7 +273,8 @@ static const JanetReg array_cfuns[] = {
"Takes a slice of array or tuple from start to end. The range is half open, "
"[start, end). Indexes can also be negative, indicating indexing from the end of the "
"end of the array. By default, start is 0 and end is the length of the array. "
- "Returns a new array.")
+ "Note that index -1 is synonymous with index (length arrtup) to allow a full "
+ "negative slice range. Returns a new array.")
},
{
"array/concat", cfun_array_concat,
diff --git a/src/core/string.c b/src/core/string.c
index f9cb04b6..f4fb92e3 100644
--- a/src/core/string.c
+++ b/src/core/string.c
@@ -525,7 +525,8 @@ static const JanetReg string_cfuns[] = {
"Returns a substring from a byte sequence. The substring is from "
"index start inclusive to index end exclusive. All indexing "
"is from 0. 'start' and 'end' can also be negative to indicate indexing "
- "from the end of the string.")
+ "from the end of the string. Note that index -1 is synonymous with "
+ "index (length bytes) to allow a full negative slice range. ")
},
{
"string/repeat", cfun_string_repeat,
diff --git a/src/core/tuple.c b/src/core/tuple.c
index c87653ac..19ce92d6 100644
--- a/src/core/tuple.c
+++ b/src/core/tuple.c
@@ -143,7 +143,10 @@ static const JanetReg tuple_cfuns[] = {
JDOC("(tuple/slice arrtup [,start=0 [,end=(length arrtup)]])\n\n"
"Take a sub sequence of an array or tuple from index start "
"inclusive to index end exclusive. If start or end are not provided, "
- "they default to 0 and the length of arrtup respectively."
+ "they default to 0 and the length of arrtup respectively. "
+ "'start' and 'end' can also be negative to indicate indexing "
+ "from the end of the input. Note that index -1 is synonymous with "
+ "index '(length arrtup)' to allow a full negative slice range. "
"Returns the new tuple.")
},
{