close #14284 document semantics for start for re,nre; improve examples (#14483)

tests/stdlib/tre.nim

@@ -0,0 +1,108 @@
+import std/re
+
+proc testAll() =
+  doAssert match("(a b c)", rex"\( .* \)")
+  doAssert match("WHiLe", re("while", {reIgnoreCase}))
+
+  doAssert "0158787".match(re"\d+")
+  doAssert "ABC 0232".match(re"\w+\s+\d+")
+  doAssert "ABC".match(rex"\d+ | \w+")
+
+  {.push warnings:off.}
+  doAssert matchLen("key", re"\b[a-zA-Z_]+[a-zA-Z_0-9]*\b") == 3
+  {.pop.}
+
+  var pattern = re"[a-z0-9]+\s*=\s*[a-z0-9]+"
+  doAssert matchLen("key1=  cal9", pattern) == 11
+
+  doAssert find("_____abc_______", re"abc") == 5
+  doAssert findBounds("_____abc_______", re"abc") == (5,7)
+
+  var matches: array[6, string]
+  if match("abcdefg", re"c(d)ef(g)", matches, 2):
+    doAssert matches[0] == "d"
+    doAssert matches[1] == "g"
+  else:
+    doAssert false
+
+  if "abc" =~ re"(a)bcxyz|(\w+)":
+    doAssert matches[1] == "abc"
+  else:
+    doAssert false
+
+  if "abc" =~ re"(cba)?.*":
+    doAssert matches[0] == ""
+  else: doAssert false
+
+  if "abc" =~ re"().*":
+    doAssert matches[0] == ""
+  else: doAssert false
+
+  doAssert "var1=key; var2=key2".endsWith(re"\w+=\w+")
+  doAssert("var1=key; var2=key2".replacef(re"(\w+)=(\w+)", "$1<-$2$2") ==
+         "var1<-keykey; var2<-key2key2")
+  doAssert("var1=key; var2=key2".replace(re"(\w+)=(\w+)", "$1<-$2$2") ==
+         "$1<-$2$2; $1<-$2$2")
+
+  var accum: seq[string] = @[]
+  for word in split("00232this02939is39an22example111", re"\d+"):
+    accum.add(word)
+  doAssert(accum == @["", "this", "is", "an", "example", ""])
+
+  accum = @[]
+  for word in split("00232this02939is39an22example111", re"\d+", maxsplit=2):
+    accum.add(word)
+  doAssert(accum == @["", "this", "is39an22example111"])
+
+  accum = @[]
+  for word in split("AAA :   : BBB", re"\s*:\s*"):
+    accum.add(word)
+  doAssert(accum == @["AAA", "", "BBB"])
+
+  doAssert(split("abc", re"") == @["a", "b", "c"])
+  doAssert(split("", re"") == @[])
+
+  doAssert(split("a;b;c", re";") == @["a", "b", "c"])
+  doAssert(split(";a;b;c", re";") == @["", "a", "b", "c"])
+  doAssert(split(";a;b;c;", re";") == @["", "a", "b", "c", ""])
+  doAssert(split("a;b;c;", re";") == @["a", "b", "c", ""])
+  doAssert(split("00232this02939is39an22example111", re"\d+", maxsplit=2) == @["", "this", "is39an22example111"])
+
+
+  for x in findAll("abcdef", re"^{.}", 3):
+    doAssert x == "d"
+  accum = @[]
+  for x in findAll("abcdef", re".", 3):
+    accum.add(x)
+  doAssert(accum == @["d", "e", "f"])
+
+  doAssert("XYZ".find(re"^\d*") == 0)
+  doAssert("XYZ".match(re"^\d*") == true)
+
+  block:
+    var matches: array[16, string]
+    if match("abcdefghijklmnop", re"(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)(k)(l)(m)(n)(o)(p)", matches):
+      for i in 0..matches.high:
+        doAssert matches[i] == $chr(i + 'a'.ord)
+    else:
+      doAssert false
+
+  block:   # Buffer based RE
+    var cs: cstring = "_____abc_______"
+    doAssert(cs.find(re"abc", bufSize=15) == 5)
+    doAssert(cs.matchLen(re"_*abc", bufSize=15) == 8)
+    doAssert(cs.matchLen(re"abc", start=5, bufSize=15) == 3)
+    doAssert(cs.matchLen(re"abc", start=5, bufSize=7) == -1)
+    doAssert(cs.matchLen(re"abc_*", start=5, bufSize=10) == 5)
+    var accum: seq[string] = @[]
+    for x in cs.findAll(re"[a-z]", start=3, bufSize=15):
+      accum.add($x)
+    doAssert(accum == @["a","b","c"])
+
+  block:
+    # bug #9306
+    doAssert replace("bar", re"^", "foo") == "foobar"
+    doAssert replace("foo", re"", "-") == "-foo"
+    doAssert replace("foo", re"$", "bar") == "foobar"
+
+testAll()