41 lines
1.2 KiB
Plaintext
Executable File
41 lines
1.2 KiB
Plaintext
Executable File
-- This is a simple and somewhat stupid example of how to switch
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-- lexers dynamically. Behind a V, X and Y are the only reserved
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-- keywords. In normal conditions, X and Y aren't keywords and can be
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-- used as variables.
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-{ block:
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require 'lexer'
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local my_lexer = lexer.lexer:clone() -- no keywords
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my_lexer:add{"X", "Y"}
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mlp.lexer:add "V"
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function num(lx)
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local a = lx:next()
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assert(a.tag=='Number')
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return a
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end
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my_parser = gg.list{
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gg.multisequence{
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{ "X", num, builder = |x| `Table{ x[1], +{0} } },
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{ "Y", num, builder = |y| `Table{ +{0}, y[1] } },
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default = gg.sequence{ mlp.id, builder = |x| `Pair{ `String{x[1][1]},`True } } },
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separators = { ',', ';' },
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builder = function(l) l.tag='Table'; return l end }
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mlp.expr:add{ "V", gg.with_lexer(my_lexer, my_parser), builder = unpack } }
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-- Use the special lexer:
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foo = V X 1, Y 2, X 3,
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for, foo, in, tag, function -- check that these aren't keywords in my_lexer
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-- Use X and Y as Id, in the unpolluted lexer:
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print "Vector:"
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X = table.tostring(foo, 60)
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print (X)
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print "Sum:" -- Ready for a functional one-liner? :)
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Y = |v| table.ifold (|a,b| table.imap (|c,d| c+d, a, b), {0,0}, v)
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table.print (Y(foo))
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