add parser combinator test; uses multiple tuples/generics features

tests/misc/tparsecombnum.nim

@@ -0,0 +1,55 @@
+import parsecomb
+
+discard """
+  output: "-289096"
+"""
+
+type Num = int
+
+# forward stuff
+var exp3: Parser[string, Num]
+var exp = lazy(proc(): Parser[string, Num] = exp3)
+
+var digit = (proc(): Parser[string, Num] =
+  result = tok("0").then(unit[string, Num](Num(0)))
+  for n in 1..9:
+    result = result + tok($n).then(unit[string, Num](Num(n)))
+)()
+
+var num = repeat1(digit).map(proc(ds: seq[Num]): Num =
+  result = 0
+  for d in ds:
+    result = result*10 + d)
+
+type Op = proc(a, b: Num): Num
+
+var plusOp = tok("+").then(unit[string, Op](proc(a, b: Num): Num = a + b))
+var minusOp = tok("-").then(unit[string, Op](proc(a, b: Num): Num = a - b))
+var timesOp = tok("*").then(unit[string, Op](proc(a, b: Num): Num = a*b))
+var divideOp = tok("/").then(unit[string, Op](proc(a, b: Num): Num = a div b))
+
+var paren = (tok("(") * exp * tok(")")).map(proc(ler: ((string, Num), string)): Num =
+  var (le, r) = ler
+  var (l, e) = le
+  e)
+
+proc foldOp(a: Num, ob: (Op, Num)): Num =
+  var (o, b) = ob
+  o(a, b)
+
+var exp0 = paren + num
+var exp1 = exp0.leftRec((timesOp + divideOp)*exp0, foldOp)
+var exp2 = exp1.leftRec((plusOp + minusOp)*exp1, foldOp)
+exp3 = exp2
+
+proc strsplit(s: string): seq[string] =
+  result = @[]
+  for i in 0 .. s.len - 1:
+    result.add($s[i])
+
+var r = exp.run("523-(1243+411/744*1642/1323)*233".strsplit)
+case r.kind:
+of rkSuccess:
+  echo r.output
+of rkFailure:
+  echo "failed"