[chaley]

27 March 2022 (In calibre version 5.40)

• The ability to define local functions. For example, the following example computes an approximate duration in years, months, days from a number of days. It uses the defined local function to_plural() to format the numbers for output.
  

  program:
  	days = 2112;
  	years = floor(days/360);
  	months = floor(mod(days, 360)/30);
  	days = days - ((years*360) + (months * 30));
  
  	def to_plural(v, str):
  		if v == 0 then return '' fi;
  		return v & ' ' & (if v == 1 then str else str & 's' fi) & ' '
  	fed;
  
  	to_plural(years, 'year') & to_plural(months, 'month') & to_plural(days, 'day')

  Notes:
  • The grammar for defining a function is
    

    function ::= 'def' function_name '(' argument_expr [',' argument_expr]* ')' ':' 
                  expression_list 'fed'
    argument_expr ::= identifier | identifier '=' expression

  • Functions must be defined before they are used.
  • The outer scope local variables are not visible inside a function.
  • The parameters in the definition can have default values.
  • You can call a function with fewer arguments than defined parameters. Parameters matched to 'missing' arguments are given their default value or the empty string if there isn't a default value.
• A 'concatenate strings' operator '&'. The expression
  

  'aaa' & 'bbb' & 'ccc'

  is equivalent to
  

  strcat('aaa', 'bbb', 'ccc')