úÎÄa Safe-InferedJThe Expr data type provides a basis for ordering mathematical operations. evalExprQ evaluates an expression tree using a list of variable definitions with values.  evalStringR evaluates a string-expression using a list of variable definitions with values.  stringToExprA parses a string-expression and returns a maybe expression tree. evalr takes a map of variable definitions and values, and a maybe expression tree, to produce maybe a numerical value.  ParserFunction-0.0.8,Text.ParserCombinators.Parsec.ParserFunctionExprVariableevalExpr evalString stringToExpr buildExpreval