Write brace blocks and statement blocks

Everywhere a macro accepts a bracketed body (macro[...]), pipescript also accepts a brace body (macro{...}). For a single expression the two are interchangeable:

>>> 5 |> f{ $ + 1 }
6

Multi-line statement blocks

The payoff of braces is that the body can be a multi-line statement block – loops, conditionals, and intermediate assignments – which a single bracketed expression cannot express. The value of the block is its final expression:

# sum 0..$ with an explicit loop
>>> 5 |> f{
    acc = 0
    for i in range($):
        acc += i
    acc
}
10

Capturing `$` into a local

Inside the block, $ keeps its usual meaning (the function’s argument). You can capture it into a local variable to reuse it – which is handy, because in the single-expression form each textual $ would otherwise introduce a fresh argument:

>>> 4 |> f{
    a = $ + 1
    a * a
}
25

Conditionals and nested pipelines

Conditionals work, and pipescript syntax nests freely inside a block, so you can drop whole pipelines into the body:

>>> 7 |> f{
    if $ % 2 == 0:
        r = 'even'
    else:
        r = 'odd'
    r
}
'odd'

>>> 10 |> f{
    half = ($ |> f[$ // 2])
    bumped = (half |> f[$ + 1])
    bumped * 100
}
600

Brace bodies compose with every macro

Statement blocks are not special to f – do, when, repeat, fork, and the rest all accept brace bodies. For the tuple-valued macros, a tuple body inside fork{...} / parallel{...} is the multi-function template, exactly as with the bracketed form:

>>> 5 |> fork{ $ + 1, $ * 2 }
(6, 10)