Constant value

Keywords: string constant, numerical constant

A constant is a numerical value (integer, float or decimal) or a string value. Numbers might be provided as integer, float or decimal values. String values may contain escape sequences for passing control characters or binary (hexadecimal) data. A detailed BNF definition for supported constants is provided below

std_constant := std_bool | std_hex | std_float | std_string

std_bool := std_false | std_true

std_false := 'false' | 'FALSE' | 'NO'

std_true := 'true' | 'TRUE' | 'YES'

std_hex := '0x' std_hexdigs

std_float := std_decimal [ std_floatp ]

std_floatp := 'E' std_integer

std_decimal := std_integer [ std_decimalp ]

std_decimalp := '.' std_digits

std_integer := std_digits | '+' std_digits | '-' std_digits

std_string := '\'' [std_str1(*)] '\'' | '"' [std_str2(*)] '"'

std_str1 := std_cchar1(*)

std_str2 := std_cchar2(*)

std_digits := std_digit(*)

std_hexdigs := std_hexdig(*)

std_cchar1 := std_dapost | std_cchar

std_dapost := '\'' | '''' | '"'

std_cchar2 := std_dquote | std_cchar

std_dquote := '\"' | '""' | '''

std_digit := '0' - '9'

std_hexdig := '0' - '9' | 'A' - 'F' | 'a' - 'f'

std_cchar := std_bss | 1-255 except: ' " \

std_bss := '\' std_bsc

std_bsc := '\' | '"' | 'n' | 't' | 'r' | 'x'

Definition:

constant ::= ref(std_constant)

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