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Some intrinsic conversions are used to convert string to string and some array to array. There are others that convert array to string as well. While the structure (whether it is a string or an array) of the output is controlled by the conversion, the input is not.
If the input is in element form (string) and the conversion takes a string as input, it would be a simple string conversion. If the input is in array form (element part missing) and the conversion takes an array as input, it would be a simple array conversion.
However, it is more complicated when the input is array form but the intrinsic conversion expects a string input, or when the input is a string but the intrinsic conversion expects an array. For a user-defined conversion, the system cannot tell whether it expects a string or an array, which adds to the complications.
To take the complication further, the array form is commonly used as a simple variable and means its default element (the one indexed by blank), and they're indistinguishable in syntax.
Here is a table to summarise the situations and how they were handled (in sequence of precedence):
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Input value |
Conversion |
How to handle |
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is an array
or simple variable
Examples:
class%name
"(array)..."
"(db)..." |
expects an array |
Convert the input as an array. |
|
expects a string |
The system will apply the conversion to each element in the input array one by one. This automatically takes care of the case of a simple variable, in which the default element will be converted. |
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is user-defined |
The system calls the user-defined function passing it the standard arguments. |
|
is a string
Examples:
class%name:elem
class%name:
"(expr)..." |
expects a string |
Convert the input as a string |
|
expects an array |
The system will take the conversion as a user-defined function and passes the standard arguments to it accordingly. |
|
is user-defined |
The system calls the user-defined function passing it the standard arguments. |
Please note that if a conversion can process both array and string, it is suggested to make the Input Value explicit array or string to avoid ambiguity. For example:
var x = -1;
display "{x:|if:@value > 0,unknown}";
The BEE Variable "x" is specified as a string (x: instead of x). Otherwise, the conversion "if" would be on the array of x, in which @value would not make sense, and the conversion would not work. This magic string-making colon is useful even in variable-less value initialization such as "{:=(expr){a} + {b}|if:@value > 10,not even ten}".
Please also note that curly bracketed variables always evaluate to a string, even the conversion output an array (in which case, the default element will be used to expand the curly bracket). If you really want to convert a string to an array, you need to use the "conv" parameter.
Example:
var myString = "abc";
var myArray = "{myString|strtoarr}"; // Got a blank
var myArray = "{myString}" conv=strtoarr; // Got an array
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