Pine Script v2 preprocessor
Algorithm of @version=2 Pine Script preprocessor in pseudo-code:
- Remove comments.
- Replace
\r\nor\rwith just\n. - Add
\nto the end of the text if it’s missing. - Lines that contain only whitespace replace with just empty strings.
- Add
|INDENT|tokens. They indicate that statement is in a block of code, such as function body,iforforbody. Every tab or four spaces are replaced with token|INDENT|. - Add
|B|and|E|tokens. They indicate line begin and line end. Replace empty lines with|EMPTY|tokens. - Join lines that represent one splitted statement.
- Add code block tokens (
|BEGIN|— beginning of the block,|END|— end of the block,|PE|— possible end of the block).
This is illustrated by example. Initial Pine Script text. Note there is
a comment //@version=2 on the first line, it’s a directive that helps
to choose correct Pine Script preprocessor/parser version.
"//@version=2
study('Preprocessor example')
fun(x, y) =>
if close > open // This line has one indent
x + y // This line has two indents
else
x - y
// Some whitespace and a comment
a = sma(close, 10)
b = fun(a, 123)
c = security(tickerid, period, b)
plot(c, title='Out', color=c > c[1] ? lime : red, // This statement will be continued on the next line
style=linebr, trackprice=true) // It's prefixed with 5 spaces, so it won't be considered as an indent
alertcondition(c > 100)"
After steps 1), 2), 3) and 4) we have:
"study('Preprocessor example')
fun(x, y) =>
if close > open
x + y
else
x - y
a = sma(close, 10)
b = fun(a, 123)
c = security(tickerid, period, b)
plot(c, title='Out', color=c > c[1] ? lime : red,
style=linebr, trackprice=true)
alertcondition(c > 100)
"
After step 5). Every 4 spaces has been replaced with |INDENT| token.
Note that 8 spaces replaced with two |INDENT| tokens and so on:
"
study('Preprocessor example')
fun(x, y) =>
|INDENT|if close > open
|INDENT||INDENT|x + y
|INDENT|else
|INDENT||INDENT|x - y
a = sma(close, 10)
b = fun(a, 123)
c = security(tickerid, period, b)
plot(c, title='Out', color=c > c[1] ? lime : red,
|INDENT| style=linebr, trackprice=true)
alertcondition(c > 100)
"
After step 6):
"|EMPTY|
|B|study('Preprocessor example')|E|
|B|fun(x, y) =>|E|
|B||INDENT|if close > open |E|
|B||INDENT||INDENT|x + y |E|
|B||INDENT|else |E|
|B||INDENT||INDENT|x - y|E|
|EMPTY|
|EMPTY|
|B|a = sma(close, 10)|E|
|B|b = fun(a, 123)|E|
|B|c = security(tickerid, period, b)|E|
|B|plot(c, title='Out', color=c > c[1] ? lime : red, |E|
|B||INDENT| style=linebr, trackprice=true) |E|
|B|alertcondition(c > 100)|E|
|EMPTY|"
After step 7). Note that line with plot(c, title= has been joined with
the next line:
"|EMPTY|
|B|study('Preprocessor example')|E|
|B|fun(x, y) =>|E|
|B||INDENT|if close > open |E|
|B||INDENT||INDENT|x + y |E|
|B||INDENT|else |E|
|B||INDENT||INDENT|x - y|E|
|EMPTY|
|EMPTY|
|B|a = sma(close, 10)|E|
|B|b = fun(a, 123)|E|
|B|c = security(tickerid, period, b)|E|
|B|plot(c, title='Out', color=c > c[1] ? lime : red, style=linebr, trackprice=true) |E|
|EMPTY|
|B|alertcondition(c > 100)|E|
|EMPTY|"
After step 8):
"|EMPTY|
|B|study('Preprocessor example')|E|
|B|fun(x, y) =>|E|
|BEGIN||B|if close > open |E|
|BEGIN||B|x + y |E||END||PE|
|B|else |E|
|BEGIN||B|x - y|E|
|EMPTY|
|EMPTY||END||PE||END||PE|
|B|a = sma(close, 10)|E|
|B|b = fun(a, 123)|E|
|B|c = security(tickerid, period, b)|E|
|B|plot(c, title='Out', color=c > c[1] ? lime : red, style=linebr, trackprice=true) |E|
|EMPTY|
|B|alertcondition(c > 100)|E|
|EMPTY|"
Done. This text is ready to be processed by Pine Script lexer and parser. There are lexer and parser grammars for your reference.
After the lexer/parser processing, we’d have an AST:
"
(FUN_CALL study (FUN_ARGS 'Preprocessor example'))
(FUN_DEF fun (FUN_DEF_EXPR (FUN_HEAD x y) (FUN_BODY (FUN_RET (IF_THEN_ELSE (> close open)
THEN (FUN_BODY (FUN_RET (+ x y)))
ELSE (FUN_BODY (FUN_RET (- x y))))))))
(VAR_DEF a (FUN_CALL sma (FUN_ARGS close 10)))
(VAR_DEF b (FUN_CALL fun (FUN_ARGS a 123)))
(VAR_DEF c (FUN_CALL security (FUN_ARGS tickerid period b)))
(FUN_CALL plot (FUN_ARGS c (KW_ARG title 'Out') (KW_ARG color (? (> c (SQBR c 1)) lime red)) (KW_ARG style linebr) (KW_ARG trackprice true)))
(FUN_CALL alertcondition (FUN_ARGS (> c 100)))
"