Evaluation priorities

Rye’s base dialect has no special forms so all code evaluates in exactly the same manner based just on types of words in a block.

Different types of words, and nothing else, do affect evaluation precedence, so understanding these basic rules will help you understand the code.

The three ways

There are three main ways to call functions, each with different evaluation behavior:

; regular words - collect arguments from the right
_+ 1 _* 2 3
; evaluates as: 1 + (2 * 3) = 7

; op-words - take first argument from the left
1 + 2 * 3
; evaluates as: 1 + (2 * 3) = 7

; pipe-words - wait for left side to fully evaluate
1 |+ 2 |* 3
; evaluates as: ((1 + 2) * 3) = 9

Op-words: right to left

The behavior described above means, Op-words (like + or .inc) evaluate from right to left. Each op-word grabs the immediate value on its left.

1 + 2 * 3
; first: 2 * 3 = 6
; then: 1 + 6 = 7

Pipe-words: left to right

Pipe-words (like |+ or |inc) wait for all expressions on the left to evaluate first, then take the result.

1 |+ 2 |* 3
; first: 1 + 2 = 3
; then: 3 * 3 = 9

Mixing them

You can mix op-words and pipe-words to control exactly how expressions evaluate:

1 + 2 |* 3
; op-word + grabs 2, pipe-word |* waits for 1 + 2
; result: (1 + 2) * 3 = 9

Using parentheses

When in doubt, parentheses give you explicit control:

( 1 + 2 ) * 3
; result: 9

With assignment

Set-words and mod-words have even higher priority than pipe-words, meaning they capture everything that follows until the end of expression (including pipe-words).

Set/Mod-words (right assignment)

x:: 1 + 2 * 3
; x = 7 (captures the whole expression)

x:: 1 |+ 2 |* 3
; x = 9 (captures the whole expression)

Left Set/Mod-words (left assignment)

Left set-words (mod-words) capture the value from left in the same manner as pipe-words do:

1 + 2 * 3 ::x
; x = 7 (captures the result)

101 ::x + 1 |+ 2 |* 3 ::y
; x = 101, y = 312
; ::x captures 101, ::y captures the final result

Combining both

You can use both set/mod-words and left set/mod-words together:

x:: 101 + y:: 1 |+ 2 |* 3
; x = 110, y = 9
; y:: captures the pipe expression (9)
; x:: captures 101 + 9 = 110

In aggregate: op-words evaluate right-to-left, pipe-words evaluate left-to-right, and set/mod-words have higher priority, capturing their respective expressions.