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| author |  Chloe Kudryavtsev <toast@toast.cafe> | 2022-01-17 19:29:00 -0500 |
|---|---|---|
| committer | Chloe Kudryavtsev <toast@toast.cafe> | 2022-01-17 19:29:00 -0500 |
| commit | 226ddb38551079a325c2abe220106e65a635e4e4 (patch) | |
| tree | 2153dc3c7422c6e4a7a43f825311f2d36d03fcc0 /examples/lmath.lua | |
| parent | add eof, patch parse to work with it (diff) | |
add eof to README
Diffstat (limited to 'examples/lmath.lua')
| -rw-r--r-- | examples/lmath.lua | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/examples/lmath.lua b/examples/lmath.lua new file mode 100644 index 0000000..2fd0535 --- /dev/null +++ b/examples/lmath.lua @@ -0,0 +1,36 @@ +local lpeg = require 'lpeg' + +-- Lexical Elements +local Space = lpeg.S(" \n\t")^0 +local Number = lpeg.C(lpeg.P"-"^-1 * lpeg.R("09")^1) * Space +local TermOp = lpeg.C(lpeg.S("+-")) * Space +local FactorOp = lpeg.C(lpeg.S("*/")) * Space +local Open = "(" * Space +local Close = ")" * Space + +-- Auxiliary function +function eval (v1, op, v2) + if (op == "+") then return v1 + v2 + elseif (op == "-") then return v1 - v2 + elseif (op == "*") then return v1 * v2 + elseif (op == "/") then return v1 / v2 + end +end + +-- Grammar +local V = lpeg.V +G = lpeg.P{ "Exp", + Exp = lpeg.Cf(V"Term" * lpeg.Cg(TermOp * V"Term")^0, eval); + Term = lpeg.Cf(V"Factor" * lpeg.Cg(FactorOp * V"Factor")^0, eval); + Factor = Number / tonumber + Open * V"Exp" * Close; +} + +local test +if arg[1] then + local f = io.open(arg[1], 'r') + test = f:read '*a' + f:close() +else + test = [[10 + 5 * 2 + 10]] +end +print(lpeg.match(G, test)) |