Colon (:)

:: Header

→full documentation

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" {ab _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;  𝕊𝕩: 𝕩÷2}

    F 3      # 𝕊n

    F 6     # 𝕊⁼𝕩

    10 F 3   # m Fn n