From 1322d612d72ac658f2aa443dca94954b819c0993 Mon Sep 17 00:00:00 2001 From: Sergio Queiroz Date: Tue, 13 Dec 2016 13:30:36 -0300 Subject: Removing example "recovery.lua" --- examples/recovery.lua | 134 -------------------------------------------------- 1 file changed, 134 deletions(-) delete mode 100644 examples/recovery.lua diff --git a/examples/recovery.lua b/examples/recovery.lua deleted file mode 100644 index bb17b54..0000000 --- a/examples/recovery.lua +++ /dev/null @@ -1,134 +0,0 @@ -local lpeg = require"lpeglabelrec" - -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 - --- The `labels` table contains the list of labels that we will be using --- as well as the corresponding error message for each label, which will --- be used in our error reporting later on. -local labels = { - {"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"}, -} - --- The `labelindex` function gives us the index of a label in the --- `labels` table, which serves as the integer representation of the label. --- We need this because LPegLabel requires us to use integers for the labels. -local function labelindex(labname) - for i, elem in ipairs(labels) do - if elem[1] == labname then - return i - end - end - error("could not find label: " .. labname) -end - --- The `errors` table will hold the list of errors recorded during parsing -local errors = {} - --- The `expect` function takes a pattern and a label and returns a pattern --- that throws the specified label if the original pattern fails to match. --- Before throwing the label, it records the label to be thrown along with --- the position of the failure (index in input string) into the `errors` table. -local function expect(patt, labname) - local i = labelindex(labname) - function recorderror(input, pos) - table.insert(errors, {i, pos}) - return true - end - return patt + Cmt("", recorderror) * T(i) -end - -local num = R("09")^1 / tonumber -local op = S("+-*/") - --- The `compute` function takes an alternating list of numbers and --- operators and computes the result of applying the operations --- to the numbers in a left to right order (no operator precedence). -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 - --- Our grammar is a simple arithmetic expression of integers that --- does not take operator precedence into account but allows grouping --- via parenthesis. We have incorporated some error recovery startegies --- to our grammar so that it may resume parsing even after encountering --- an error, which allows us to report more errors. -local g = P { - "Exp", - Exp = Ct(V"Term" * (C(op) * V"OpRecov")^0) / compute; - -- `OpRecov` handles missing terms/operands by returning a dummy (zero). - OpRecov = Lc(V"Operand", Cc(0), labelindex("ExpTerm")); - Operand = expect(V"Term", "ExpTerm"); - Term = num + V"Group"; - -- `Group` handles missing closing parenthesis by simply ignoring it. - -- Like all the others, the error is still recorded of course. - Group = "(" * V"InnerExp" * Lc(expect(")", "MisClose"), P"", labelindex("MisClose")); - -- `InnerExp` handles missing expressions by skipping to the next closing - -- parenthesis. A dummy (zero) is returned in place of the expression. - InnerExp = Lc(expect(V"Exp", "ExpExp"), (P(1) - ")")^0 * Cc(0), labelindex("ExpExp")); -} - -g = expect(g, "NoExp") * expect(-P(1), "Extra") - --- The `eval` function takes an input string to match against the grammar --- we've just defined. If the input string matches, then the result of the --- computation is returned, otherwise we return the error messages and --- positions of all the failures encountered. -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 = labels[err[1]][2] - table.insert(out, "syntax error: " .. msg .. " (at index " .. pos .. ")") - end - errors = {} - return nil, table.concat(out, "\n") - 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 (at index 11) - -print(eval "(1+)-1*(2/2)") ---> syntax error: expected a term after the operator (at index 4) - -print(eval "(1+1)-1*(/2)") ---> syntax error: expected an expression after the parenthesis (at index 10) - -print(eval "1+(1-(1*2))/2x") ---> syntax error: extra chracters found after the expression (at index 14) - -print(eval "-1+(1-(1*2))/2") ---> syntax error: no expression found (at index 1) - -print(eval "(1+1-1*(2/2+)-():") ---> syntax error: expected a term after the operator (at index 13) ---> syntax error: expected an expression after the parenthesis (at index 16) ---> syntax error: missing a closing ')' after the expression (at index 17) ---> syntax error: extra characters found after the expression (at index 17) -- cgit v1.2.3-55-g6feb