StartsWith and IsStartOf (String functions)

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Is the method object string an initial substring of the argument string? (String class) [introduced in Sirius Mods 7.9 βeta]


%boolean = string:IsStartOf( longerString, MinLength= number)

Syntax terms

%boolean The Boolean result of IsStartOf is True if:
  • The length of the method object string is at least the value of the MinLength argument
  • the method object string is the same as the initial substring, whose length is the length of string, of the longerString argument.
If either of the above conditions does not hold, the result is False.
string A string which is examined to see if it is an abbreviation (i.e., an initial substring) of longerString.
longerString A string which is examined to see if the method object string is an abbreviation of it.
MinLength This name-required argument is a non-negative number, specifying the minimum length of the method object string to be considered an abbreviation of longerString. Note that if this is 0, then the null string is an abbreviation of any value of the longerString argument; if this is non-0, then the null string is never an abbreviation.


Determining if option is valid abbreviation

A common task is checking user input for a valid abbreviation for one of several longer terms. This is one motivation for the MinLength argument; there may be overlap in the initial substrings of the longer terms. Consider the following fragment:

%opt = %(system):arguments:toUpper if %opt:isStartOf('MAXAMOUNT', 5) then ... elseIf %opt:isStartOf('MAXTIME', 5) then ... else PrintText Invalid argument: {%opt}

If the argument to this proc is max, that would not distinguish it between maxAmount and maxTime; hence the MinLength argument value of 5 is used to enforce that at least maxAm or maxTi is entered (a value of 4 would also have disambiguated the abbreviations in this case).

Several single-line examples

The following fragment:

PrintText {~= 'a':IsStartOf('abc', 1) } PrintText {~= 'a':IsStartOf('abc', 2) } PrintText {~= 'a':IsStartOf('abc', 0) } PrintText {~= 'x':IsStartOf('abc', 1) } PrintText {~= 'x':IsStartOf('abc', 0) } PrintText {~= :IsStartOf('abc', 0) }

produces the following output:

'a':IsStartOf('abc', 1) = True 'a':IsStartOf('abc', 2) = False 'a':IsStartOf('abc', 0) = True 'x':IsStartOf('abc', 1) = False 'x':IsStartOf('abc', 0) = False

See also