This is a handy little table over how values behave when coerced to another type, eg. things like !2 or true > (). Vertical is the type of the value being coerced and horizontal is the type being coerced to. Coercion is implemented in coercion.rs.
Blank spaces indicate that the coercion is invalid.
| Number | Bool | Function | String | |
|---|---|---|---|---|
| Number | same value | true |
||
| Bool | true => 1, false => 0 |
same value | ||
| Function | true |
same value | ||
| String | true |
same value | ||
| Nil | 0 |
false |
Unlike languages like Javascript, numbers are always truthy, and only nil is falsey. This makes checking for nil simple and consistent in terms of behavior (if x). It is worth noting that the opposite is not true for coercing bools into numbers, so coercing a number into a bool and then back into a number will not return the same value as what it started with.
There is technically a nil type, but is impossible to coerce anything to it and every coercion to it fails, even nil to itself.
When a program exits, the return value from the main function will be attempted to be coerced into a number using a set of special rules. This coercion will always succeed to prevent the program from crashing at the very last moment.
| Value | Exit code |
|---|---|
| Number | same value |
| Bool | true => 0, false => 1 |
| Function | 0 |
| String | 0 |
| Nil | 0 |
Notably, the coercion from bool is flipped compared to normal coercion. Returning a bool can be read as "did the program succeed?".
Equality comparisons using == always compare values plainly, they do not perform any coercion, so two values of different types will never be equal.