Add maxsplit

README.asciidoc

@@ -54,7 +54,7 @@ Variants:
  - `proc findAllStr(...)` returns a `seq[string]`
 
 [[proc-split]]
-==== split(string, Regex): seq[string]
+==== split(string, Regex, maxsplit = -1): seq[string]
 
 Splits the string with the given regex. This works according to the rules that
 Perl and Javascript use.
@@ -63,6 +63,8 @@ Perl and Javascript use.
     `"123".split(r"") == @["1", "2", "3"]`.
   - If the pattern has a capture in it, it is added after the string split:
     `"12".split(re"(\d)") == @["", "1", "", "2", ""]`.
+  - If `maxsplit != -1`, then the string will only be split `maxsplit` times.
+    `"123".split(re"", maxsplit = 1) == @["1", "23"]`
 
 [[proc-replace]]
 ==== replace(string, Regex, sub): string

src/nre.nim

@@ -384,9 +384,10 @@ proc renderBounds(str: string, bounds: Slice[int]): string =
   for i in bounds.a .. bounds.b:
     result.add("^")
 
-proc split*(str: string, pattern: Regex): seq[string] =
+proc split*(str: string, pattern: Regex, maxSplit = -1): seq[string] =
   result = @[]
   var lastIdx = 0
+  var splits = 0
 
   for match in str.findIter(pattern):
     # upper bound is exclusive, lower is inclusive:
@@ -405,6 +406,7 @@ proc split*(str: string, pattern: Regex): seq[string] =
       discard
     else:
       result.add(str.substr(lastIdx, bounds.a - 1))
+      splits += 1
 
     lastIdx = bounds.b
 
@@ -412,6 +414,9 @@ proc split*(str: string, pattern: Regex): seq[string] =
       # if there are captures, include them in the result
       result.add(cap)
 
+    if splits == maxSplit:
+      break
+
   # last match: Each match takes the previous substring,
   # but "1 2".split(/ /) needs to return @["1", "2"].
   # This handles "2"

test/split.nim

@@ -11,3 +11,8 @@ suite "string splitting":
 
   test "captured patterns":
     check("12".split(re"(\d)") == @["", "1", "", "2", ""])
+
+  test "maxsplit":
+    check("123".split(re"", maxsplit = 1) == @["1", "23"])
+    check("123".split(re"", maxsplit = 0) == @["123"])
+    check("123".split(re"", maxsplit = -1) == @["1", "2", "3"])