Update three-line-table.md

docs/FAQ/three-line-table.md

@@ -3,6 +3,8 @@ tags: [table]
 ---
 # 如何实现三线表？
 
+## 手动方法
+
 使用 `stroke: none` 隐藏默认边框，然后使用 `table.hline()` 画线即可。
 
 ```typst
@@ -16,5 +18,52 @@ tags: [table]
   [g], [h], [i],
   table.hline(),
 )
+```
+
+## 封装成函数
+
+来源：https://forum.typst.app/t/is-there-any-simple-way-of-creating-a-three-line-table-like-latex/1193/8
+
+```typst
+#let three-line-table = it => {
+  if it.children.any(c => c.func() == table.hline) {
+    return it
+  }
+
+  let toprule = table.hline(stroke: 0.08em)
+  let bottomrule = toprule
+  let midrule = table.hline(stroke: 0.05em)
 
+  let meta = it.fields()
+  meta.stroke = none
+  meta.remove("children")
+
+  let header = it.children.find(c => c.func() == table.header)
+  let cells = it.children.filter(c => c.func() == table.cell)
+  if header == none {
+    let columns = meta.columns.len()
+    header = table.header(..cells.slice(0, columns))
+    cells = cells.slice(columns)
+  }
+
+  return table(
+    ..meta,
+    toprule,
+    header,
+    midrule,
+    ..cells,
+    bottomrule,
+  )
+}
+
+#show table: three-line-table
+
+#table(
+  columns: 2,
+  align: center,
+  table.header([*Name*], [*Made public*]),
+  [Typst], [2023],
+  [LaTeX], [1984],
+  [TeX], [1978]
+)
 ```