57 lines
2.1 KiB
Ruby
57 lines
2.1 KiB
Ruby
require_relative "basic_types"
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require_relative "tokens"
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require_relative "keywords"
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module Parser
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# obviously a work in progress !!
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# We "compose" the parser from bits, divide and hopefully conquer
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class Composed < Parslet::Parser
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include BasicTypes
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include Tokens
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include Keywords
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# a note about .maybe : .maybe is almost every respect the same as .repeat(0,1)
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# so either 0, or 1, in other words maybe. Nice feature, but there are strings attached:
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# a maybe removes the 0 a sequence (array) to a single (hash). Thus 2 transformations are needed
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# More work than the prettiness is worth, so only use .maybe on something that does not need capturing
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rule(:argument_list) {
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left_parenthesis >>
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((expression.as(:argument) >> (comma >> expression.as(:argument)).repeat(0)).repeat(0,1)).as(:argument_list) >>
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right_parenthesis
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}
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rule(:function_call) { name.as(:function_call) >> argument_list }
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rule(:assignment) { name.as(:asignee) >> equal_sign >> expression.as(:asigned) }
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rule(:expression) { conditional | function_call | integer | string | (name >> space? >> equal_sign.absent?) }
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def delimited_expressions( delimit )
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( space? >> (delimit.absent? >> (assignment | expression)).repeat(1)).as(:expressions) >> delimit
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end
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rule(:conditional) {
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keyword_if >> left_parenthesis >> expression.as(:conditional) >> right_parenthesis >>
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delimited_expressions(keyword_else).as(:if_true) >>
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delimited_expressions(keyword_end).as(:if_false)
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}
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rule(:expressions_else) { delimited_expressions(keyword_else) }
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rule(:expressions_end) { delimited_expressions(keyword_end) }
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rule(:function_definition) {
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keyword_def >> name.as(:function_definition) >> parmeter_list >> expressions_end
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}
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rule(:parmeter_list) {
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left_parenthesis >>
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((name.as(:parmeter) >> (comma >> name.as(:parmeter)).repeat(0)).repeat(0,1)).as(:parmeter_list) >>
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right_parenthesis
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}
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rule(:root){ function_definition | expression | assignment }
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end
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end
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