Add ignore function

src/test.nim

@@ -61,7 +61,7 @@ proc initParser(str: string): ParserResult =
   Parser(
     state: ParserState(
       stream: str,
-      position: 0,
+      position: -1,
       lastPosition: 0,
     ),
     tokens: newSeq[Token](),
@@ -70,32 +70,65 @@ proc initParser(str: string): ParserResult =
 func ch(c1: char): (Parser -> ParserResult) {.inline.} =
   return func(parser: Parser): ParserResult =
     let state = parser.state
-    let c2 = state.stream[state.position]
+    let newIndex = state.position + 1
+
+    if newIndex > (state.stream.len - 1):
+      return err((parser, &"Expected {c1} at {newIndex}, got End of string"))
+    else:
+      let c2 = state.stream[newIndex]
 
       if c1 == c2:
         return Parser(
           state: ParserState(
             stream: state.stream,
-          position: state.lastPosition + 1,
+            position: newIndex,
             lastPosition: parser.state.position,
           ),
           tokens: parser.tokens & Token(value: c2)
         ).ok()
       else:
-      return err((parser, &"Expected {c2} at {state.lastPosition}, got {c1}"))
+        return err((parser, &"Expected {c2} at {newIndex}, got {c1}"))
 
+func ignore(parserFn: Parser -> ParserResult): (Parser -> ParserResult) {.inline.} =
+  ## Parse characters but throw success tokens away
+  return proc(parser: Parser): ParserResult =
+    return parserFn(parser)
+    .map((x: Parser) => Parser(
+      state: x.state,
+      tokens: parser.tokens,
+    ))
 
 proc parseSeq(parser: ParserResult, xs: seq[Parser -> ParserResult]): ParserResult =
   xs.foldl(a.flatMap(b), parser)
 
+func str(s: string): (Parser -> ParserResult) {.inline.} =
+  return func(parser: Parser): ParserResult =
+    var p = parser.ok()
+    for c in s.items:
+      p = p.flatMap(ch(c))
+    return p
+
+# func str(s1: string): (Parser -> ParserResult) {.inline.} =
+#   return func(parser: Parser): ParserResult =
+#     return parser.flatMap(x => parseSeq(@[ch('F')]))
+
 # type R = Result[int, string]
 
 # echo R.ok 4
 
-let fooParser = initParser("FOO").parseSeq(@[
+# let i = 3
-  ch('F'),
+
-  ch('O'),
+# echo $("FOO"[i])
-  ch('O'),
+
+let fooParser = initParser("FOO_BAR").parseSeq(@[
+  str("FOO"),
+  ignore(ch('_')),
+  ignore(ch('_')),
+  ignore(ch('_')),
+  ignore(ch('_')),
+  ch('B'),
+  ch('A'),
+  ch('R'),
 ])
 
 echo fooParser