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Examples > Calculator > Tokens


The tokens for the operators and the parenthesis are defined directly inside of the productions.


"+", "-", "*","/","(", ")"


A complex token for the recognition of numbers is defined as a regular expression on the token page:


number  = \d+(\.\d*)?|\.\d+


"\d" a single digit

"\d+" a repeat of digits, at least one

"\." the dot (without backslash '\' the dot has a special meaning inside of a regular expression).

"\d*" a repeat of digits, or no digit

"?" an optional occurrence of the content of the preceding parenthesis

"|" an alternative


So a number is defined either as a sequence of digits, optional followed by a dot followed by null or more digits ( e.g: "123" or "123." or "123.45"). Or a number begins with a dot followed by a sequence of digits (e.g.: ".45")



This page belongs to the TextTransformer Documentation

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