Yes

src/test.nim

@@ -2,6 +2,7 @@ import std/options
 import std/strutils
 import std/strformat
 import std/collections/sequtils
+import std/sugar
 import results
 import fusion/matching
 import fp/maybe
@@ -35,7 +36,7 @@ type
 
 proc indentKey(x: string, count: int): string =
   var y = x.indent(count)
-  y.delete(0, count - 1)
+  y.delete(0..count - 1)
   y
 
 proc `$`*(x: Token): string =
@@ -45,15 +46,15 @@ proc `$`*(x: Token): string =
 
 proc `$`*(x: ParserState): string =
   &"""ParserState(
-    stream: {x.stream},
+  stream: "{x.stream}",
   position: {x.position},
   lastPosition: {x.lastPosition},
 )"""
 
 proc `$`*(x: Parser): string =
   &"""Parser(
-    state: {indentKey($x.state, 4)},
+  state: {indentKey($x.state, 2)},
-    tokens: {x.tokens}
+  tokens: {indentKey($x.tokens, 2)},
 )"""
 
 proc initParser(str: string): ParserResult =
@@ -79,13 +80,17 @@ proc ch(parser: Parser, c: char): ParserResult =
       tokens: parser.tokens & Token(value: c)
     ).ok()
   else:
-    err((parser, "Foo"))
+    err((parser, &"Expected {c}"))
 
 # type R = Result[int, string]
 
 # echo R.ok 4
 
+
 echo initParser("Foo")
+  .flatMap((x: Parser) => ch(x, c = 'F'))
+  .flatMap((x: Parser) => ch(x, c = 'o'))
+  .flatMap((x: Parser) => ch(x, c = 'o'))
 
 # proc parseStars