57 lines
1.8 KiB
Markdown
57 lines
1.8 KiB
Markdown
---
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title: Grammar
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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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```
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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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<bool> ::= true | false
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```
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## Expressions
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The following gives no typing information. You can obey the grammar and still write nonsensical code.
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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>
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<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> | <bool> | <symbol> | ( <expr> ) | <array> | <record> | <record>.<symbol> | <symbol> => <expr> | (<symbol>, <symbol>) => <expr> | ... | <symbol>(<symbol>) | <symbol>(<symbol>, <symbol>) | ...
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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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<statement> ::= <assign> | <assignFunction>
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<assign> ::= <symbol> = <expr>
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<assignFunction> ::= <symbol>(<symbol>) = <expr> | <symbol>(<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> | <statement> <delim> <expr> | <statement> <delim> <statement> <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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