View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0000906 | LDMud 3.7 | Runtime | public | 2022-04-28 20:29 | 2022-04-28 20:29 |
| Reporter | Gnomi | Assigned To | |||
| Priority | normal | Severity | feature | Reproducibility | always |
| Status | new | Resolution | open | ||
| Platform | i686 | OS | Debian GNU/LInux | OS Version | 5.0 |
| Summary | 0000906: Revise default-initialization of float variables | ||||
| Description | TLDR: Initialize floats with integer 0 and prevent arithmetic on this value with RTTCs. Since LDMud 3.2.11 and 3.3.585 floats are default-initialized with 0.0, whereas all other types are initialized with 0. This brings some inconsistent behavior: T var; if (!var) { write("Uninitialized.\n"); } For all T (like string, or float|closure) this will print the string, but not for T = float. The reasons for the change are unknown. This might have been a suggestion for more intuitive behavior in the following cases or just preventing type inconsistencies there: float var; return (var + 1) / 2 var++; var += 2; Previously those expressions would have resulted in 0, 1, 2 as integers, now the result is 0.5, 1.0 and 2.0 as floats. The change hides an underlying problem with doing arithmetic on the default-zero. In the above example we could initialize var explicitly with 0 and get the old behavior, thus violating the type restrictions. Also the following code still "works" in LDMud 3.6.5: string var; var+=2; And results in var being 2. So in order to remove the default-initialization to 0.0, we need to have a different solution for the arithmetic. Let's start with getting the semantics right. Do we want to do automatic conversion on assignment: string var = 2; // Error or "2"? float var = 2; // Error or 2.0? I would vote 'no', otherwise 'string var = 0;' becomes a tricky case. Also it makes runtime behavior very dependent on the knowledge about the type (so pragma save_types might have a heavy influence) and union types will complicate matters. Do we want to do automatic conversion on usage: float var; return (var + 1) / 2; // 0 or 0.5? Same argument is before: Making runtime behavior dependent on the knowledge of the type seems a bad idea. Combination of the above questions for +=: string var; var += 2; float var; var += 2; This should have the same meaning as 'var = var + 2;', so it depends on the previous answers. So in the end I would suggest to: 1. Remove the 0.0 initialization 2. Add RTTC checks to ++, --, +=, -= But this would break stuff and would only be detectable at runtime... | ||||
| Tags | No tags attached. | ||||
