evaluation - pannous/warp GitHub Wiki

Evaluation turns code into values. A program is code and is evaluated; a data file is data and is not. When each part of a program is evaluated (values now, charged code at every use, uncharged blocks only with !), and the vocabulary, are specified in charged.

• Call arguments are evaluated before the call, except for parameters declared block.
• ( … ) groups are evaluated on the spot; { … } is data or a block by default; [ … ] lists evaluate their elements.
• x! runs a block once, x!! fully (full-evaluation); do x is x! (do).
• The compiler computes pure parts as early as it can (constant folding, hoisting, memoization; compiler-only, no user memoization syntax); this never changes what a program observes (charged section 3). Effects such as State and Eval block that path (effects).
• The shell can keep assignments symbolic and show the evaluation step by step.

Related keywords: result (the last value), it (the implicit argument).

calling a function value

A closure is called by giving it a group on the right: ((x -> x * 2) 7) is 14. Since a group of one element is the element itself, (x) == x, there is an ambiguity if the parentheses are omitted.