Lazily evaluated (late-binding) definition for Dyalog APL

True lazy (late-binding) editable, SALTable, Linkable, ⎕FIXable definition

This user command allows defintion of arrays and tacit functions in a lazy manner, which means that their definitions are not evaluated until runtime. This allows editing, SALTing, Linking, ⎕FIXing, and commenting both arrays and tacit functions, and allows tacit top-down programming.

Installation

• Download Lazy.dyalog to a location
• From within Dyalog APL issue <code>]Settings cmddir ,location -permanent</code>

Usage

]Lazy          ⍝ list all lazy definitions
]Lazy fn       ⍝ show lazy definition
]Lazy fn←code  ⍝ define lazily

Examples

]Lazy Avg←Sum÷1⌈≢     ⍝ allowed even though Sum is not defined yet
]Lazy Sum←+⌿
]Lazy matrix←3 4⍴⍳12  ⍝ formula will be kept rather than executed, so this array is dynamically ⎕IO-dependent