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evaluator

0.1.1
0.1.3 retired 0.1.2 0.1.1 0.1.0 retired

A SQL92 predicate expression evaluator in Erlang

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evaluator src expression_lexer.xrl
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src/expression_lexer.xrl 

Definitions.



WS = [\s\t\r\n]



REGULAR_IDENTIFIER = [a-zA-Z][_a-zA-Z0-9]*

QUOTED_IDENTIFIER = \"([^\"]|\"\")*\"


DELIMITED_IDENTIFIER = \[([^\[\]]|\[\[|\]\])+\]





INTEGER_CONSTANT = [0-9]+


DECIMAL_CONSTANT = [0-9]+\.[0-9]+


NUMBER_CONSTANT = [0-9]+(\.[0-9]+)?[eE][-+]?[0-9]+


BOOLEAN_CONSTANT = ([tT][rR][uU][eE])|([fF][aA][lL][sS][eE])


STRING_CONSTANT = '([^']|'')*'





ESCAPE = [eE][sS][cC][aA][pP][eE]





NOT = [nN][oO][tT]


AND = [aA][nN][dD]


OR = [oO][rR]





EQ = =


NEQ = <>


NEQ2 = !=


GT = >


GTE = >=


LT = <


LTE = <=





EXISTS = [eE][xX][iI][sS][tT][sS]





IS = [iI][sS]


IN = [iI][nN]


LIKE = [lL][iI][kK][eE]


NULL = [nN][uU][lL][lL]





O_PARENTHESES = \(


C_PARENTHESES = \)


DOT = \.


COMMA = ,


PLUS = \+


MINUS = -


MULTIPLY = \*


DIVIDE = \/


PERCENT = %





Rules.





{WS} : skip_token.





{NULL} : t(t_null, TokenLine, TokenChars).





{EQ} : t(t_eq, TokenLine, TokenChars).


{NEQ} : t(t_neq, TokenLine, TokenChars).


{NEQ2} : t(t_neq, TokenLine, TokenChars).


{GT} : t(t_gt, TokenLine, TokenChars).


{GTE} : t(t_gte, TokenLine, TokenChars).


{LT} : t(t_lt, TokenLine, TokenChars).


{LTE} : t(t_lte, TokenLine, TokenChars).





{IS} : t(t_is, TokenLine, TokenChars).


{IN} : t(t_in, TokenLine, TokenChars).


{LIKE} : t(t_like, TokenLine, TokenChars).


{EXISTS} : t(t_exists, TokenLine, TokenChars).





{O_PARENTHESES} : t(o_parentheses, TokenLine, TokenChars).


{C_PARENTHESES} : t(c_parentheses, TokenLine, TokenChars).





{DOT} : t(t_dot, TokenLine, TokenChars).


{COMMA} : t(t_comma, TokenLine, TokenChars).





{PLUS} : t(t_plus, TokenLine, TokenChars).


{MINUS} : t(t_minus, TokenLine, TokenChars).


{MULTIPLY} : t(t_multiply, TokenLine, TokenChars).


{DIVIDE} : t(t_divide, TokenLine, TokenChars).


{PERCENT} : t(t_percent, TokenLine, TokenChars).





{ESCAPE} : t(t_escape, TokenLine, TokenChars).





{NOT} : t(t_not, TokenLine, TokenChars).


{AND} : t(t_and, TokenLine, TokenChars).


{OR} : t(t_or, TokenLine, TokenChars).





{INTEGER_CONSTANT} : t(integer_constant, TokenLine, TokenChars).


{DECIMAL_CONSTANT} : t(decimal_constant, TokenLine, TokenChars).


{NUMBER_CONSTANT} : t(approximate_number_constant, TokenLine, TokenChars).


{BOOLEAN_CONSTANT} : t(boolean_constant, TokenLine, TokenChars).


{STRING_CONSTANT} : t(string_constant, TokenLine, unquote_string_constant(TokenChars)).





{REGULAR_IDENTIFIER} : t(regular_identifier, TokenLine, TokenChars).


{QUOTED_IDENTIFIER} : t(quoted_identifier, TokenLine, unquote_quoted_identifier(TokenChars)).


{DELIMITED_IDENTIFIER} : t(delimited_identifier, TokenLine, unquote_delimited_identifier(TokenChars)).





Erlang code.





t(TokenType, TokenLine, TokenChars) -> { token, {TokenType, TokenLine, TokenChars } }.





unquote_delimited_identifier(Identifier) ->


    Len = string:len(Identifier),


    Text = string:substr(Identifier, 2, Len - 2),


    re:replace(


        re:replace(Text, "\\[\\[", "[", [global, { return, list }]),  


        "\\]\\]", 


        "]", 


        [global, { return, list }])


.





unquote_quoted_identifier(Identifier) ->


    Len = string:len(Identifier),


    Text = string:substr(Identifier, 2, Len - 2),


    re:replace(Text, "\"\"", "\"", [global, { return, list }])

.



unquote_string_constant(String) ->

    Len = string:len(String),

    Text = string:substr(String, 2, Len - 2),

    re:replace(Text, "''", "'", [global, { return, list }])    

.