There surely are strings that can be converted into numbers (even something as simple as “1”). But in general, when languages do implicit conversions, they do it towards the more general type.
For example, if I do 1.1 == 1 in pretty much any language that has separate float and int types, the integer gets casted into a float (from more specific to more general type) and the comparison returns false. It would be utterly ridiculous if the language auto-casts the float to int and then returns true.
JS does just that. Instead of casting the more general number into a string and comparing that, it goes the other way round.
Every number has an equivalent string representation, not every string has an equivalent number representation.
Not quite. As the previous commenter said, every string has at least one string representation (i.e. 100 -> “100”, “1e2”). So there’s no sensible way to write a pure function handling that, you’re just cooked no matter what you do.
Implicit cast from number to string, explicit parsing in the other direction.
For comparisons as number, parse the string to a number and compare two numbers.
The main point of the implicit cast from number to string is to concattenate number to string, e.g. print("testValue: " + testValue).
Another option (e.g. taken by Python) is to acknowledge that there’s no pure 1:n mapping in any direction between string and number, so any conversion between those two needs to be done explicitly. That’s probably the most correct implementation, but it makes string concattenation annoying. But then again, f-strings and similar techniques make that problem pretty much obsolete.
There surely are strings that can be converted into numbers (even something as simple as “1”). But in general, when languages do implicit conversions, they do it towards the more general type.
For example, if I do
1.1 == 1in pretty much any language that has separate float and int types, the integer gets casted into a float (from more specific to more general type) and the comparison returns false. It would be utterly ridiculous if the language auto-casts the float to int and then returns true.JS does just that. Instead of casting the more general number into a string and comparing that, it goes the other way round.
Every number has an equivalent string representation, not every string has an equivalent number representation.
Not quite. As the previous commenter said, every string has at least one string representation (i.e. 100 -> “100”, “1e2”). So there’s no sensible way to write a pure function handling that, you’re just cooked no matter what you do.
Other languages handle that easily:
Implicit cast from number to string, explicit parsing in the other direction.
For comparisons as number, parse the string to a number and compare two numbers.
The main point of the implicit cast from number to string is to concattenate number to string, e.g.
print("testValue: " + testValue).Another option (e.g. taken by Python) is to acknowledge that there’s no pure 1:n mapping in any direction between string and number, so any conversion between those two needs to be done explicitly. That’s probably the most correct implementation, but it makes string concattenation annoying. But then again, f-strings and similar techniques make that problem pretty much obsolete.