grammar
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packages/website/docs/Internal/Grammar.md
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packages/website/docs/Internal/Grammar.md
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---
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title: Grammar
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urlcolor: blue
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author:
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- Quinn Dougherty
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---
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Formal grammar specification, reference material for parser implementation.
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_In all likelihood the reference will have to be debugged as we see what tests pass and don't pass during implementation_.
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## Lexical descriptions of constants and identifiers
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- `<number>` ::= `[-]? [0-9]+ (.[0-9]+)? | [-]? [0-9]+ (.[0-9]+)? [e] [-]? [0-9]+`
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- `<symbol>` ::= `[a-zA-Z]+ [a-zA-Z0-9]?`
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- `<baseDistribution>` ::= `(normal(<number>, <number>) | beta(<number>, <number>) | triangular(<number>, <number>, <number>) | cauchy(<number>, <number>) | lognormal(<number>, <number>)) | uniform(<number>, <number>) | <number> to <number> | exponential(<number>)`
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## Expressions
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Think of javascript's list unpacking notation to read our variable-argument function `mixture`.
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```
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<expr> ::= <term> + <expr> | <term> - <expr> | <expr> .+ <expr> | <expr> .- <expr> | <term> | sample(<baseDistribution>) | mixture(...<array>, <array>) | mx(...<array>, <array>) | exp(<expr>) | log(<expr>, <number>?) | log10(<expr>) | dotLog(<expr>, <number>?) | normalize(<expr>)
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<term> ::= <power> * <term> | <power> <term> | <power> / <term> | <power> .* <term> | <power ./ <term> | <power>
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<power> ::= <factor> ^ <power> | <factor> .^ <power> | <factor>
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<factor> ::= <number> | <baseDistribution> | <symbol> | ( <expr> )
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```
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## Data structures
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```
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<array> ::= [] | [<expr>] | [<expr>, <expr>] | ...
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<record> ::= {} | {<symbol>: <expr>} | {<symbol>: <expr>, <symbol>: <expr>} | ...
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```
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## Statements
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```
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<stmnt> ::= <asgn> | <asgnFn>
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<asgn> ::= <symbol> = <expr>
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<asgnFn> ::= <symbol>(<symbol>) = <expr>
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```
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## A squiggle file
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To be valid and raise no errors as of current (apr22) interpreter,
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```
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<delim> ::= ; | \n
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<code> ::= <expr> | <stmnt> <delim> <expr> | <stmnt> <delim> <stmnt> <delim> <expr> | ...
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```
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This isn't strictly speaking true; the interpreter allows expressions outside of the final line.
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