Commit 4bf5361caa7b6b927a8e5c0256c07ae6c184115c - s-cargot

Fixed type and semantic errors Getty Ritter 9 years ago

1 changed file(s) with 5 addition(s) and 4 deletion(s). Collapse all Expand all

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README.md less more

135	135	As pointed out above, there are three different carrier types that are
136	136	used to represent S-expressions by the library, but you can use any
137	137	type as a carrier type for a spec. This is particularly useful when
138		you want to do your own parsing. For example, if we wanted to parse
139		a small S-expression-based arithmetic language, we could define a
140		data type and transformations from and to an S-expression type:
	138	you want to parse into your own custom tree-like type. For example, if
	139	we wanted to parse a small S-expression-based arithmetic language, we
	140	could define a data type and transformations from and to an S-expression
	141	type:
141	142
142	143	~~~~.haskell
143	144	import Data.Char (isDigit)

151	152	toExpr (RSAtom c)
152	153	\| T.all isDigit c = pure (Num (read (T.unpack c)))
153	154	\| otherwise = Left "Non-numeric token as argument"
154		toExpr _ = "Unrecognized s-expr"
	155	toExpr _ = Left "Unrecognized s-expr"
155	156
156	157	fromExpr :: Expr -> RichSExpr Text
157	158	fromExpr (Add x y) = RSList [RSAtom "+", fromExpr x, fromExpr y]