Rules that decide whether your text compiles

One statement, one line

A newline ends a statement. That is true inside an argument list too, so a call split over several lines is a parse error. Write the call on one line however long it becomes.

// Rejected: "Expected expression, found"
plot.line(
  ta.sma(close, 20),
  "#22C55E"
)

// Accepted
plot.line(ta.sma(close, 20), "#22C55E", 2, "solid")

Braces open on the same line

The opening brace of an if branch or a function body must sit on the same line as the condition or the signature. A closing brace may be followed by else on the same line or on the next line. Chained else if is supported. When only a value depends on the condition, the conditional expression condition ? a : b is shorter than a branch.

if close > open {
  plot.marker(true, high, "#22C55E", "triangle", "above", 8, 2)
} else if close < open {
  plot.marker(true, low, "#EF4444", "triangle", "below", 8, 2)
} else {
  plot.marker(true, close, "#9CA3AF", "diamond", "above", 8, 2)
}

Declarations live at the top level

A top level let or var declares a series, and a series must be declared at the top level of the script, never inside an if branch. Inside an if branch you may assign to an existing var with := or a compound operator such as +=, and you may call plot functions. Inside a function body or a loop body, let declares a local instead: a plain value for the rest of that block, which may be reassigned.

// Rejected: "Series declarations must be top level"
if close > open {
  let body: float = close - open
}

// Accepted
var up_bars: float = 0
up_bars := nz(up_bars[1], 0)
if close > open {
  up_bars += 1
}

Other lexical rules

• Comments start with // and run to the end of the line. There is no block comment.
• Strings use double quotes, cannot span lines, and support the escapes \n, \t, \" and \\.
• Numbers may be decimal or scientific, for example 12, 0.25, .5 and 1e3.
• Identifiers use letters, digits and underscore, and cannot start with a digit. let, var, if, else, fn, return, true, false, while and for are reserved words. to, by, break and continue only mean something where a loop uses them.
• math.pi, math.e and the colour names color.aqua, color.black, color.blue, color.fuchsia, color.gray, color.green, color.lime, color.maroon, color.navy, color.olive, color.orange, color.purple, color.red, color.silver, color.teal, color.white and color.yellow are constants, written without parentheses.
• Builtin names such as ta.sma and plot.line are single names. The dot is part of the name, not property access.
• A semicolon also separates statements, so two short statements may share a line.
• The source is UTF-8 and is limited to 65,536 bytes.