Pattern Matching #76
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Pattern Matching #76
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- Error messages did not properly chunkID the source filename, leading to @'s next to filenames and such. - LoadFile improperly raised a generic file read error, even if the actual error was a Lua error such as a SyntaxError.
Currently implements only a very limited subset of `gmatch`. Yes, there is a goto in this commit - it was in the original codebase.
In the original C version of match, there is a label after the default case that can be jumped into from above. The goto implementation in Go does not allow us to jump to that label in all cases. So instead, we form a closure from the default case that we can call into anyplace.
Enabling pattern-matching tests also opened the door to fixing a couple of parsing bugs and filling out a few additional features, such as +, *, and $.
- Implement balanced string and frontier matching. - Fix error messages to actually show up. - Fix a few nasty out of bounds slice accesses. - Run gmatch against the very last position of the source string.
The original version of match() used goto labels to avoid recursive function calls and keep control over the stack size. However, Go cannot jump from one block to another, so the original location of the "dflt" label was unusable. Until this commit, I worked around this deficiency with a closure, but this made the code harder to follow and "out-of-order" compared to the original codebase. The closure is gone, and instead we move the default case of the main switch out into the parent block, reintroducing the old "dflt" label. In cases where we do not want to execute the "dflt" label, we skip over it with a new label that goes straight to the "end" of the function.
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Hello, Any update with this PR? Why is not merged? Thanks |
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So yeah, pattern matching. Hooray.
gotoin the main match function in order to keep the stack under control, and this has been preserved with slight alterations in order to accommodate Go's stricter rules on where you can and can't jump to. In my research, it appears that Go stacks are (nearly) infinite, but I'm not sure that means converting the jumps to recursive function calls is necessarily a good idea..Also, my apologies, but I actually started this branch midway through #67, so I would merge that before looking at this. I also added a little helpful bit to the Lua test harness that returns the error string off the stack if one exists when running the test suite - if you would rather that be in a separate pull request, it can be backed out.