123 lines
2.6 KiB
Lua
123 lines
2.6 KiB
Lua
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local m = require"lpeglabel"
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local re = require"relabel"
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local num = m.R("09")^1 / tonumber
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local op = m.S("+-")
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local labels = {}
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local nlabels = 0
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local function newError(lab, msg, psync, pcap)
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nlabels = nlabels + 1
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psync = psync or m.P(-1)
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pcap = pcap or m.P""
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labels[lab] = { id = nlabels, msg = msg, psync = psync, pcap = pcap }
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end
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newError("ExpTermFirst", "expected an expression", op + ")", m.Cc(1000))
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newError("ExpTermOp", "expected a term after the operator", op + ")", m.Cc(1000))
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newError("MisClose", "missing a closing ')' after the expression", m.P")")
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newError("Extra", "extra characters found after the expression")
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local errors, subject
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local function expect(patt, labname)
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local i = labels[labname].id
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return patt + m.T(i)
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end
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local function compute(tokens)
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local result = tokens[1]
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for i = 2, #tokens, 2 do
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if tokens[i] == '+' then
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result = result + tokens[i+1]
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elseif tokens[i] == '-' then
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result = result - tokens[i+1]
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else
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error('unknown operation: ' .. tokens[i])
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end
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end
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return result
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end
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local g = m.P {
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"Exp",
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Exp = m.Ct(m.V"OperandFirst" * (m.C(op) * m.V"Operand")^0) / compute,
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OperandFirst = expect(m.V"Term", "ExpTermFirst"),
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Operand = expect(m.V"Term", "ExpTermOp"),
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Term = num + m.V"Group",
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Group = "(" * m.V"Exp" * expect(")", "MisClose"),
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}
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function recorderror(pos, lab)
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local line, col = re.calcline(subject, pos)
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table.insert(errors, { line = line, col = col, msg = labels[lab].msg })
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end
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function record (labname)
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return (m.Cp() * m.Cc(labname)) / recorderror
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end
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function sync (p)
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return (-p * m.P(1))^0
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end
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function defaultValue (p)
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return p or m.Cc(1000)
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end
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local grec = g * expect(m.P(-1), "Extra")
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for k, v in pairs(labels) do
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grec = m.Rec(grec, record(k) * sync(v.psync) * v.pcap, v.id)
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end
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local function eval(input)
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errors = {}
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io.write("Input: ", input, "\n")
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subject = input
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local result, label, suffix = grec:match(input)
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io.write("Syntactic errors found: " .. #errors, "\n")
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if #errors > 0 then
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local out = {}
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for i, err in ipairs(errors) do
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local pos = err.col
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local msg = err.msg
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table.insert(out, "syntax error: " .. msg .. " (at index " .. pos .. ")")
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end
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print(table.concat(out, "\n"))
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end
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io.write("Result = ")
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return result
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end
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print(eval "90-70-(5)+3")
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--> 18
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print(eval "15+")
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--> 2 + 0
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print(eval "-2")
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--> 0 - 2
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print(eval "1+3+-9")
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--> 1 + 3 + [0] - 9
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print(eval "1+()3+")
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--> 1 + ([0]) [+] 3 + [0]
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print(eval "8-(2+)-5")
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--> 8 - (2 + [0]) - 5
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print(eval "()")
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print(eval "")
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print(eval "1+()+")
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print(eval "1+(")
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print(eval "3)")
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print(eval "11+()3")
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--> 1 + ([0]) [+] 3 + [0]
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