Remember that data is any of null, boolean, integer, float, string, array of data, object mapping string to data (i.e. JSON). We do not provide separate types for these JSON cases.

Operators

+

Syntax: expr + expr

Typing: data + data -> data

Cases:

• one null: the result is null
• two numbers: the numbers are added. If the numbers are both integers, it is tried to return the result as integer, otherwise it is fallen back to a floating-point result
• two strings: the strings are concatenated
• a string with a number: the number is converted to string, and then the two strings are concatenated
• two arrays: the arrays are concatenated
• two objects: the fields from the second object are added to the fields of the first object, overriding any existing field of the same name

, , /, %

Syntax: expr - expr (for the other operators in the same way)

Typing: data - data -> data (for the other operators in the same way)

Cases:

• one null: the result is null
• two numbers:

• subtraction: the numbers are subtracted. If the numbers are both integers, it is tried to return the result as integer, otherwise it is fallen back to a floating-point result
• multiplication: same way
• division: this is always a floating-point division
• modulus: this is always a floating-point division remainder

++

Syntax: expr ++ expr

Typing: T* ++ T* -> T*

Returns a stream that first takes the elements from the first input, and then from the second input after no more element can be retrieved from the first.

Hint: because the type-checker converts T to T* automatically, any of the inputs can also be a non-stream. For example 1 ++ 2 ++ 3 constructs a stream of the three elements 1, 2, and 3. Or, all ++ "end" returns the elements from all followed by the single string "end".

&& and ||

Syntax: expr && expr or expr || expr

Typing: data && data -> data