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toot-toot: more verbose but clearer cursor_down 

I actually got all tests to pass on the first try.
This commit is contained in:
Kartik K. Agaram 2021-12-22 18:44:03 -08:00
parent 77b464fbf0
commit 2c76aa9ff0
1 changed files with 45 additions and 17 deletions
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62
toot-toot.tlv
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@ -261,28 +261,56 @@
- __teliva_timestamp: original
cursor_down:
>function cursor_down(s, old_idx)
> local colidx = 0
> local old_colidx = -1
> for i=1,string.len(s) do
> local max = string.len(s)
> local i = 1
> -- compute oldcol, the screen column of old_idx
> local oldcol = 0
> local col = 0
> while true do
> if i > max then
> -- abnormal old_idx
> return old_idx
> end
> if i == old_idx then
> old_colidx = colidx
> elseif colidx == old_colidx then -- next line
> oldcol = col
> break
> end
> if s[i] == '\n' then
> col = 0
> else
> col = col+1
> end
> i = i+1
> end
> -- skip rest of line
> while true do
> if i > max then
> -- current line is at bottom
> return old_idx
> end
> if s[i] == '\n' then
> break
> end
> i = i+1
> end
> -- compute index at same column on next line
> -- i is at a newline
> i = i+1
> col = 0
> while true do
> if i > max then
> -- next line is at bottom and is too short; position at end of it
> return i
> end
> -- loop update
> if s[i] == '\n' then
> if old_colidx ~= -1 and old_colidx > colidx then
> return i
> end
> colidx = 0
> else
> colidx = colidx+1
> -- next line is too short; position at end of it
> return i
> end
> end
> if old_colidx == colidx then
> return string.len(s)+1
> else
> return old_idx
> if col == oldcol then
> return i
> end
> col = col+1
> i = i+1
> end
>end
>