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| author | Sergio Queiroz <sqmedeiros@gmail.com> | 2016-12-07 08:50:03 -0300 |
|---|---|---|
| committer | Sergio Queiroz <sqmedeiros@gmail.com> | 2016-12-07 08:50:03 -0300 |
| commit | 2ea15094a1d4a9f422c983480aab7231951ee20e (patch) | |
| tree | 119348d9249fa8bbc6ef3b5223cc12f34f179697 /examples | |
| parent | a4bdec34353ad1849f99e6ab0e5f2ad5e74c83b1 (diff) | |
| download | lpeglabel-2ea15094a1d4a9f422c983480aab7231951ee20e.tar.gz lpeglabel-2ea15094a1d4a9f422c983480aab7231951ee20e.tar.bz2 lpeglabel-2ea15094a1d4a9f422c983480aab7231951ee20e.zip | |
Renaming files and removing example based on another version
Diffstat (limited to 'examples')
| -rw-r--r-- | examples/expRec.lua (renamed from examples/expressionRecovery.lua) | 0 | ||||
| -rw-r--r-- | examples/expRecAut.lua (renamed from examples/expressionRecAut.lua) | 0 | ||||
| -rw-r--r-- | examples/expect.lua | 98 |
3 files changed, 0 insertions, 98 deletions
diff --git a/examples/expressionRecovery.lua b/examples/expRec.lua index c5cbcca..c5cbcca 100644 --- a/examples/expressionRecovery.lua +++ b/examples/expRec.lua | |||
diff --git a/examples/expressionRecAut.lua b/examples/expRecAut.lua index e098078..e098078 100644 --- a/examples/expressionRecAut.lua +++ b/examples/expRecAut.lua | |||
diff --git a/examples/expect.lua b/examples/expect.lua deleted file mode 100644 index cb68d38..0000000 --- a/examples/expect.lua +++ /dev/null | |||
| @@ -1,98 +0,0 @@ | |||
| 1 | local lpeg = require"lpeglabel" | ||
| 2 | |||
| 3 | local R, S, P, V, C, Ct, T = lpeg.R, lpeg.S, lpeg.P, lpeg.V, lpeg.C, lpeg.Ct, lpeg.T | ||
| 4 | |||
| 5 | -- The `labels` table contains the list of labels that we will be using | ||
| 6 | -- as well as the corresponding error message for each label, which will | ||
| 7 | -- be used in our error reporting later on. | ||
| 8 | local labels = { | ||
| 9 | {"NoExp", "no expression found"}, | ||
| 10 | {"Extra", "extra characters found after the expression"}, | ||
| 11 | {"ExpTerm", "expected a term after the operator"}, | ||
| 12 | {"ExpExp", "expected an expression after the parenthesis"}, | ||
| 13 | {"MisClose", "missing a closing ')' after the expression"}, | ||
| 14 | } | ||
| 15 | |||
| 16 | -- The `expect` function takes a pattern and a label defined in | ||
| 17 | -- the `labels` table and returns a pattern that throws the specified | ||
| 18 | -- label if the original pattern fails to match. | ||
| 19 | -- Note: LPegLabel requires us to use integers for the labels, so we | ||
| 20 | -- use the index of the label in the `labels` table to represent it. | ||
| 21 | local function expect(patt, labname) | ||
| 22 | for i, elem in ipairs(labels) do | ||
| 23 | if elem[1] == labname then | ||
| 24 | return patt + T(i) | ||
| 25 | end | ||
| 26 | end | ||
| 27 | |||
| 28 | error("could not find label: " .. labname) | ||
| 29 | end | ||
| 30 | |||
| 31 | local num = R("09")^1 / tonumber | ||
| 32 | local op = S("+-*/") | ||
| 33 | |||
| 34 | -- The `compute` function takes an alternating list of numbers and | ||
| 35 | -- operators and computes the result of applying the operations | ||
| 36 | -- to the numbers in a left to right order (no operator precedence). | ||
| 37 | local function compute(tokens) | ||
| 38 | local result = tokens[1] | ||
| 39 | for i = 2, #tokens, 2 do | ||
| 40 | if tokens[i] == '+' then | ||
| 41 | result = result + tokens[i+1] | ||
| 42 | elseif tokens[i] == '-' then | ||
| 43 | result = result - tokens[i+1] | ||
| 44 | elseif tokens[i] == '*' then | ||
| 45 | result = result * tokens[i+1] | ||
| 46 | elseif tokens[i] == '/' then | ||
| 47 | result = result / tokens[i+1] | ||
| 48 | else | ||
| 49 | error('unknown operation: ' .. tokens[i]) | ||
| 50 | end | ||
| 51 | end | ||
| 52 | return result | ||
| 53 | end | ||
| 54 | |||
| 55 | -- Our grammar is a simple arithmetic expression of integers that | ||
| 56 | -- does not take operator precedence into account but allows grouping | ||
| 57 | -- via parenthesis. | ||
| 58 | local g = P { | ||
| 59 | "Exp", | ||
| 60 | Exp = Ct(V"Term" * (C(op) * expect(V"Term", "ExpTerm"))^0) / compute; | ||
| 61 | Term = num + V"Group"; | ||
| 62 | Group = "(" * expect(V"Exp", "ExpExp") * expect(")", "MisClose"); | ||
| 63 | } | ||
| 64 | |||
| 65 | g = expect(g, "NoExp") * expect(-P(1), "Extra") | ||
| 66 | |||
| 67 | -- The `eval` function takes an input string to match against the grammar | ||
| 68 | -- we've just defined. If the input string matches, then the result of the | ||
| 69 | -- computation is returned, otherwise we return the error message and | ||
| 70 | -- position of the first failure encountered. | ||
| 71 | local function eval(input) | ||
| 72 | local result, label, suffix = g:match(input) | ||
| 73 | if result ~= nil then | ||
| 74 | return result | ||
| 75 | else | ||
| 76 | local pos = input:len() - suffix:len() + 1 | ||
| 77 | local msg = labels[label][2] | ||
| 78 | return nil, "syntax error: " .. msg .. " (at index " .. pos .. ")" | ||
| 79 | end | ||
| 80 | end | ||
| 81 | |||
| 82 | print(eval "98-76*(54/32)") | ||
| 83 | --> 37.125 | ||
| 84 | |||
| 85 | print(eval "(1+1-1*2/2") | ||
| 86 | --> syntax error: missing a closing ')' after the expression (at index 11) | ||
| 87 | |||
| 88 | print(eval "(1+)-1*(2/2)") | ||
| 89 | --> syntax error: expected a term after the operator (at index 4) | ||
| 90 | |||
| 91 | print(eval "(1+1)-1*(/2)") | ||
| 92 | --> syntax error: expected an expression after the parenthesis (at index 10) | ||
| 93 | |||
| 94 | print(eval "1+(1-(1*2))/2x") | ||
| 95 | --> syntax error: extra chracters found after the expression (at index 14) | ||
| 96 | |||
| 97 | print(eval "-1+(1-(1*2))/2") | ||
| 98 | --> syntax error: no expression found (at index 1) | ||
