Adding relabel example with error recovery

1 files changed, 114 insertions, 0 deletions

diff --git a/examples/expectWithRecovRe.lua b/examples/expectWithRecovRe.lua
new file mode 100644
index 0000000..c424160
--- /dev/null
+++ b/examples/expectWithRecovRe.lua
@@ -0,0 +1,114 @@
+local lpeg = require"lpeglabel"
+local re = require"relabel"
+
+local R, S, P, V = lpeg.R, lpeg.S, lpeg.P, lpeg.V
+local C, Cc, Ct, Cmt = lpeg.C, lpeg.Cc, lpeg.Ct, lpeg.Cmt
+local T, Lc = lpeg.T, lpeg.Lc
+
+local errinfo = {
+  {"NoExp",     "no expression found"},
+  {"Extra",     "extra characters found after the expression"},
+  {"ExpTerm",   "expected a term after the operator"},
+  {"ExpExp",    "expected an expression after the parenthesis"},
+  {"MisClose",  "missing a closing ')' after the expression"},
+}
+
+local labels = {}
+local errmsgs = {}
+
+for i, err in ipairs(errinfo) do
+  labels[err[1]] = i
+  errmsgs[err[1]] = err[2]
+end
+
+re.setlabels(labels)
+
+local errors = {}
+
+function recordError(input, pos, label)
+  table.insert(errors, {label, pos})
+  return true
+end
+
+local function compute(tokens)
+  local result = tokens[1]
+  for i = 2, #tokens, 2 do
+    if tokens[i] == '+' then
+      result = result + tokens[i+1]
+    elseif tokens[i] == '-' then
+      result = result - tokens[i+1]
+    elseif tokens[i] == '*' then
+      result = result * tokens[i+1]
+    elseif tokens[i] == '/' then
+      result = result / tokens[i+1]
+    else
+      error('unknown operation: ' .. tokens[i])
+    end
+  end
+  return result
+end
+
+local g = re.compile([[
+  S         <- (Exp / ErrNoExp) (!. / ErrExtra)
+  Exp       <- {| Term (op Operand)* |} -> compute
+  Operand   <- Term / ErrExpTerm /{ExpTerm} dummy
+  Term      <- num / Group
+  Group     <- "(" InnerExp (")" / ErrMisClose /{MisClose} "")
+  InnerExp  <- Exp / ErrExpExp /{ExpExp} [^)]* dummy
+
+  op   <- {[-+*/]} 
+  num  <- [0-9]+ -> tonumber
+
+  ErrNoExp     <- ("" -> "NoExp"     => recordError) %{NoExp}
+  ErrExtra     <- ("" -> "Extra"     => recordError) %{Extra}
+  ErrExpTerm   <- ("" -> "ExpTerm"   => recordError) %{ExpTerm}
+  ErrExpExp    <- ("" -> "ExpExp"    => recordError) %{ExpExp}
+  ErrMisClose  <- ("" -> "MisClose"  => recordError) %{MisClose}
+
+  dummy <- "" -> "0" -> tonumber
+]], {
+  compute = compute;
+  recordError = recordError;
+  tonumber = tonumber;
+})
+
+local function eval(input)
+  local result, label, suffix = g:match(input)
+  if #errors == 0 then
+    return result
+  else
+    local out = ""
+    for i, err in ipairs(errors) do
+      local pos = err[2]
+      local msg = errmsgs[err[1]]
+      local line, col = re.calcline(input, pos)
+      out = out .. "syntax error: " .. msg .. " (line " .. line .. ", col " .. col .. ")\n"
+    end
+    errors = {}
+    return nil, out
+  end
+end
+
+print(eval "98-76*(54/32)")
+--> 37.125
+
+print(eval "(1+1-1*2/2")
+--> syntax error: missing a closing ')' after the expression (line 1, col 10)
+
+print(eval "(1+)-1*(2/2)")
+--> syntax error: expected a term after the operator (line 1, col 4)
+
+print(eval "(1+1)-1*(/2)")
+--> syntax error: expected an expression after the parenthesis (line 1, col 10)
+
+print(eval "1+(1-(1*2))/2x")
+--> syntax error: extra characters found after the expression (line 1, col 14)
+
+print(eval "-1+(1-(1*2))/2")
+--> syntax error: no expression found (line 1, col 1)
+
+print(eval "(1+1-1*(2/2+)-():")
+--> syntax error: expected a term after the operator (line 1, col 13)
+--> syntax error: expected an expression after the parenthesis (line 1, col 16)
+--> syntax error: missing a closing ')' after the expression (line 1, col 17)
+--> syntax error: extra characters found after the expression (line 1, col 17)