Conditionals

A conditional shows content only when the data agrees. (if @path is value) … (end) compares; (if @path) … (end) tests truthiness. Use them for status banners, draft asides, and gated variants.

Comparison

#book: { status - draft }

(if @book.status is draft) DRAFT WATERMARK (end)

That renders the watermark. The comparison keyword is is or equals — they are exact synonyms. There is no other operator: no ==, !=, <, >, and no not, and, or, or contains.

Equality coerces to strings

The right-hand side is a bareword or number, and equality stringifies both sides. So a number compares equal to its digits:

#meter: { value - 99 }

(if @meter.value is 99) ON TARGET (end)

That is true — the number 99 stringifies to 99. A record or collection stringifies to the empty string, so a container never equals a literal (compare-against-string).

Existence and truthiness

Drop the operator to test whether a value is present and truthy:

#book: { flag - true }

(if @book.flag) TRUTHY (end)

The falsy set is: missing or unresolved, the empty string, the string false, the number 0, boolean false, null, an empty record {}, and an empty collection []. Everything else is truthy.

Else, empties, and nesting

An (else) branch is optional:

#book: { status - draft }

(if @book.status equals final) FINAL (else) NOT FINAL (end)

That renders NOT FINAL. Empty then or else branches are legal no-ops (empty-then-body, empty-else-body), and ifs nest with their own (end):

(if @lamp.lit)
  (if @lamp.oil is full) BRIGHT (end)
(end)

(nested-ifs; if-end-basic for the plain then-only form.)

The glued-statement gotcha

Because statements need whitespace before the (, a statement glued to a preceding ) is not recognised and renders literally:

(each @xs as x)(if @x is a)Y(end)(end)   ~ inner (if …) prints as text
(each @xs as x) (if @x is a) Y (end) (end)   ~ works

Always separate adjacent statements with a space or newline.

Common mistakes

• Reaching for contains, <, >, and, or or — none exist.
• Comparing a whole record to a literal — a container stringifies to empty and never matches.
• Gluing (if to a preceding ) — keep a space.

See also

· Data access · Type-classified scalars · Faceted content · Gotchas