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CLEX_LANGUAGE.md

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Grammar Rules for Clex Generator

Written similar to regex, just so that regex doesn't support Repeating Things through Back-references and Regex is unnecessary complex.

Refer clex specsfor more detailed explanation.

Rules

Meta-characters

  • ()?:\{}[],'

Character Sets

  • SPACE = WHITESPACE | e
  • N = Integer (-infinity to infinity)
  • F = Float (-infinity.sth to infinity.sth)
  • S = Non-whitespace String
  • C = Non-whitespace Character

Misc character

  • Literal non-negative numbers (to denote ranges/no. of occurrences/back-referencing etc.)
  • 'A' := Literal Characters, currently being in used only in string modifier expression

Special Functions

  • () => Capturing Group Indexed by 1
  • (?:) => Non-capturing Group
  • \1 => Back-reference
  • (?:.....){} => Specify the number of occurrences of the group
  • N|F[m, n] => Specifying min and max values of N or F (Skip one of the values means MIN and MAX respectively), check for the string if it is within the range or not
  • S[l,c] => Specifying the length(l) and character set of String i.e. Alphabets, Alphanumeric, Numeric, Uppercase, Lowercase, Newline, All. If c is not specified then defaults to ALphanumeric.

Rule

  • Capturing group can only have single non-negative INTEGER element. If not specified its min value is set to 0.

Language

Current Design

  • PROGRAM := Vector<UNIT_EXPRESSION>

  • UNIT_EXPRESSION := PRIMARY_DATA_TYPE(PRIMARY_DATA_TYPE, REFERENCE_TYPE) | CAPTURING_GROUP(POSITIVE NUMBER, PRIMARY_DATA_TYPE) | NON_CAPTURING_GROUP(Vec<UNIT_EXPRESSION>, REFERENCE_TYPE) | EOF

  • PRIMARY_DATA_TYPE(REFERENCE_TYPE) := INTEGER(REFERENCE_TYPE, REFERENCE_TYPE) | FLOAT(REFERENCE_TYPE, REFERENCE_TYPE) | CHARACTER | STRING(REFERENCE_TYPE, CHARACTER_SET)

  • CAPTURING_GROUP := PRIMARY_DATA_TYPE(1)::NUMERAL_TYPE(0|POSITIVE_NUMBER, MAX_VALUE)::INTEGER

  • NON_CAPTURING_GROUP(REFERENCE_TYPE) := Vector<PRIMARY_DATA_TYPE | NON_CAPTURING_GROUP | CAPTURING_GROUP>

  • REFERENCE_TYPE := BY_GROUP(GROUP_NO) | BY_COUNT(POSITIVE_NUMBER) | NONE

  • CHARACTER_SET := 'U' | 'L' | 'n' | '0'..='9' | 'D' | 'N' | CHARACTERS

  • MIN_VALUE, MAX_VALUE is of type Integer

  • POSITIVE_NUMBER is non-negative Integer

  • Vector -> Similar to Variable Sized Array

Old Designs

  • NCG = (:?EXPRESSION)

  • CG = (N[0,])

  • RE = EXPRESSION{\NATURAL_LITERAL_NUMBER}|{NATURAL_LITERAL_NUMBER}

  • RBP = N|F[LITERAL_NUMBER|e,LITERAL_NUMBER|e]

  • EXPRESSION = CG|NCG|PRIMITIVE_TYPES|RBP|RE

  • PRIMITIVE_TYPES = N|F|S|C

  • LITERAL_NUMBER = Any Integral numbers like -2, 0, 5 etc

  • NATURAL_LITERAL_NUMBER = Only Positive Integers like 1, 5 etc

  • e stands for epsilon or null

Acronyms

  • NCG = Non Capturing Group
  • CG = Capturing Group
  • RBP = Range Bound Primitive
  • RE = Repeating Expressions

Example Usage

Here are some example usages of the clex language:

  • (N) N[,1000] (?:N F S){\1} : Accepts input like "2 2 2 2.2 ABC2 3 4.5 ASD". Description: It expects two integers (say k1 and k2 with k2<=1000) followed by triplets of Integer, Float and String, occurring as many times as specified by the first capturing group(k1).

  • (N[,1000]){\2}: Valid usage.

  • (?:N[,1000]{\2}): Valid usage.

  • (?:N{\2}[,1000]): Invalid usage.

  • (N F) => Invalid, Capturing Group can only contain a single non-negative number only, else put it in non-capturing one

References

For more details on the clex language and advanced usage, you can refer to the following references: