Add ;:? to keybar and help

1 files changed, 20 insertions, 0 deletions

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+*View this file with results and syntax highlighting [here](https://mlochbaum.github.io/BQN/help/header.html).*
+
+# Colon (`:`)
+
+## `:`: Header
+[→full documentation](../doc/block.md#block-headers)
+
+Placed at the end of a block header. A header has syntax that matches the way the block is called. It indicates the block type, and number and structure of inputs.
+
+        "xy" {a‿b _op c: b} ∞
+
+Multiple bodies are searched in order to find one with a matching header.
+
+        F ← {m Fn n: m+Fn n;  𝕊n: 2×n;  𝕊⁼𝕩: 𝕩÷2}
+
+        F 3      # 𝕊n
+
+        F⁼ 6     # 𝕊⁼𝕩
+
+        10 F 3   # m Fn n