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| author | Case Duckworth | 2024-04-01 22:16:50 -0500 |
|---|---|---|
| committer | Case Duckworth | 2024-04-01 22:16:50 -0500 |
| commit | f28763f3afcd2c51e9b69318e3749b6bb0a4f1ea (patch) | |
| tree | ed4ab2f55fa3854cd33f1954b9faf02fda507b25 /type.lua | |
| parent | Error on wrong unquote[-splicing] (diff) | |
| download | lam-f28763f3afcd2c51e9b69318e3749b6bb0a4f1ea.tar.gz lam-f28763f3afcd2c51e9b69318e3749b6bb0a4f1ea.zip | |
Implement list length
This lays groundwork for arity checks.
Diffstat (limited to 'type.lua')
| -rw-r--r-- | type.lua | 14 |
1 files changed, 14 insertions, 0 deletions
| diff --git a/type.lua b/type.lua index 3c26188..07f78f1 100644 --- a/type.lua +++ b/type.lua | |||
| @@ -97,6 +97,20 @@ function m.cons (a, b) | |||
| 97 | end | 97 | end |
| 98 | return "(" .. table.concat(out, " ") .. ")" | 98 | return "(" .. table.concat(out, " ") .. ")" |
| 99 | end, | 99 | end, |
| 100 | __len = | ||
| 101 | function (self) | ||
| 102 | local function go (lis, acc) | ||
| 103 | -- improper lists don't have lengths | ||
| 104 | -- ... but don't error here. | ||
| 105 | if not m.isa(lis, "cons") then | ||
| 106 | return nil | ||
| 107 | end | ||
| 108 | if lis[2] == m.null then return acc | ||
| 109 | else return go(lis[2], acc+1) | ||
| 110 | end | ||
| 111 | end | ||
| 112 | return go(self, 1) | ||
| 113 | end, | ||
| 100 | } | 114 | } |
| 101 | return setmetatable(t, mt) | 115 | return setmetatable(t, mt) |
| 102 | end | 116 | end |