For example, a list element with opt-name background specifies an option that can be specified on the command line using the long option --background. Further information about the option — whether it takes a value, whether it is required to be present in the command line, and so on — is specified by the option properties.
In the example of the preceding section, we already saw that a long option name can have a equivalent short option character.
The value property specifies whether an option requires option specification accepts a value. If the value property is set to t, the option requires a value: getopt-long will signal an error if the option name is present without a corresponding value.
If set to f, the option does not take a value; in this case, a non-option word that follows the option name in the command line will option specification treated as a non-option argument. If the option name for an option with ' value optional is immediately option specification in the command line by another option name, the value for the first option is implicitly t.
The required? If the required?
Finally, the predicate property can be used to constrain the possible values of an option. If used, the predicate property should be set to a procedure that takes one argument — the proposed option value as a string — and returns either t or f according as the proposed value is or is not acceptable.
Minimum of options contracts Order Types Currently, only the market and limit orders are accepted by the matching engine. A post-only order will always enter the order book without being instantly matched. If the order were to be matched, our trading engine would adjust the order so that it enters the order book at the next best possible price.
If the predicate procedure returns f, getopt-long will signal an error. By default, options do not have single-character equivalents, are not required, and do not take values.
FREE Course Reveals Our Options Trading Tips Get the exact step-by-step formula we use for our high-probability strategies to generate consistent income Like any formal agreement between two parties, option contracts clearly delineate all of the parameters of the contract between buyer and seller.
Where the list element for an option includes a value property but no predicate property, the option values are unconstrained.