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A pipe reads in the order things happen, and `_` shows where the value goes

Nested calls read inside out: in format_cents(with_tax(discounted(2500, 10), 8)) the first step is in the middle and the last is on the left. The pipe value |> step feeds a value into the next step, so the steps read top to bottom in the order they run. A step marks the value's slot with _, so you never guess which argument it fills; a bare function name, like format_cents, takes the value as its only argument. A call with no _ is an error rather than a guess.

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fn price_label(cents: i32) -> string: cents |> discounted(_, 10) # ← `_` is where the value goes |> with_tax(_, 8) |> format_centspub fn main() -> void $ Console: println(price_label(2500)) # The same steps, nested, read inside out: println(format_cents(with_tax(discounted(2500, 10), 8)))# Change `discounted(_, 10)` to `discounted(10)` and Run. A step never# guesses where the value goes:# pipe-step-needs-placeholder: write `_` where the piped value goes# ── plumbing ──fn discounted(cents: i32, percent: i32) -> i32: cents * (100 - percent) / 100fn with_tax(cents: i32, percent: i32) -> i32: cents + cents * percent / 100fn format_cents(cents: i32) -> string: "$${cents / 100}.${(cents % 100).to_string().pad_start(2, '0')}"

A pipe reads in the order things happen, and _ shows where the value goes

A pipe reads in the order things happen, and `_` shows where the value goes