Added startsWith/endsWith implementations for character prefix/suffix (fixes #4252).

lib/pure/strutils.nim

@@ -862,6 +862,10 @@ proc startsWith*(s, prefix: string): bool {.noSideEffect,
     if s[i] != prefix[i]: return false
     inc(i)
 
+proc startsWith*(s: string, prefix: char): bool {.noSideEffect.} =
+  ## Returns true iff ``s`` starts with ``prefix``.
+  result = s[0] == prefix
+
 proc endsWith*(s, suffix: string): bool {.noSideEffect,
   rtl, extern: "nsuEndsWith".} =
   ## Returns true iff ``s`` ends with ``suffix``.
@@ -874,6 +878,10 @@ proc endsWith*(s, suffix: string): bool {.noSideEffect,
     inc(i)
   if suffix[i] == '\0': return true
 
+proc endsWith*(s: string, suffix: char): bool {.noSideEffect.} =
+  ## Returns true iff ``s`` ends with ``suffix``.
+  result = s[s.high] == suffix
+
 proc continuesWith*(s, substr: string, start: Natural): bool {.noSideEffect,
   rtl, extern: "nsuContinuesWith".} =
   ## Returns true iff ``s`` continues with ``substr`` at position ``start``.
@@ -2029,4 +2037,12 @@ bar
     # Don't use SI prefix as number is too small
     doAssert formatEng(3.1e-25, siPrefix=true, unit="A") == "310e-27 A"
 
+  block: # startsWith / endsWith char tests
+    var s = "abcdef"
+    doAssert s.startsWith('a')
+    doAssert s.startsWith('b') == false
+    doAssert s.endsWith('f')
+    doAssert s.endsWith('a') == false
+    doAssert s.endsWith('\0') == false
+
   #echo("strutils tests passed")