standard

Essential utility functions for measuring size, converting values, and handling errors.

Standard Functions

Essential utility functions available in every SAPL policy for common operations like measuring collection sizes, converting values to strings, and handling errors gracefully.

Error Handling

Use onErrorMap to provide fallback values when expressions might fail:

policy "safe division"
permit
where
    var ratio = standard.onErrorMap(resource.count / resource.total, 0);
    ratio > 0.5;

Measuring Size

The length function works uniformly across text, arrays, and objects:

policy "limit items"
deny
    action == "add_item" & standard.length(resource.cart) >= 100;

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length

length(ARRAY|TEXT|JSON value): For TEXT it returns the length of the text string. For ARRAY, it returns the number of elements in the array. For OBJECT, it returns the number of keys in the OBJECT. For NUMBER, BOOLEAN, or NULL, the function will return an error.

Example:

policy "example"
permit
  standard.length([1, 2, 3, 4]) == 4;
  standard.length("example") == 7;
  standard.length({ "key1" : 1, "key2" : 2}) == 2;

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toString

toString(value): Converts any value to a string representation.

Example:

policy "example"
permit
  standard.asString([1,2,3]) == "[1,2,3]";

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onErrorMap

onErrorMap(guardedExpression, fallbackExpression): If evaluation of guardedExpression results in an error, the fallback is returned instead. Otherwise the result of guardedExpression is returned.

Example:

policy "example"
permit
  standard.onErrorMap(1/0,999) == 999;

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