diff options
Diffstat (limited to 'util.lua')
| -rw-r--r-- | util.lua | 34 |
1 files changed, 34 insertions, 0 deletions
@@ -91,4 +91,38 @@ function util.write_json_file(path, data) f:close() end +-- merges tables `t' and `u', using key `k' for identity. the order from `u' is +-- always respected, preserving the relative order from `t' when possible. +function util.stable_kmerge(t, u, k) + local pos = {} + for i, v in ipairs(u) do + pos[v[k]] = i + end + + local res = {} + local seen = {} + local function append(v) + if not seen[v[k]] then + res[#res+1] = v + seen[v[k]] = true + end + end + + local ind = 1 + for _, v in ipairs(t) do + if pos[v[k]] then + while ind <= pos[v[k]] do + append(u[ind]) + ind = ind + 1 + end + end + append(v) + end + for i = ind, #u do + append(u[i]) + end + + return res +end + return util |