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Add vector.to_string and vector.from_string (#10323)

Writing vectors as strings is very common and should belong to `vector.*`. `minetest.pos_to_string` is also too long to write, implies that one should only use it for positions and leaves no spaces after the commas.
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Desour committed Apr 5, 2021
1 parent 19c2835 commit 23325277659132e95b346307b591c944625bda16
Showing with 45 additions and 0 deletions.
  1. +19 −0 builtin/common/tests/vector_spec.lua
  2. +16 −0 builtin/common/vector.lua
  3. +10 −0 doc/lua_api.txt
@@ -48,6 +48,25 @@ describe("vector", function()
assert.same({ x = 41, y = 52, z = 63 }, vector.offset(vector.new(1, 2, 3), 40, 50, 60))
end)

it("to_string()", function()
local v = vector.new(1, 2, 3.14)
assert.same("(1, 2, 3.14)", vector.to_string(v))
end)

it("from_string()", function()
local v = vector.new(1, 2, 3.14)
assert.same({v, 13}, {vector.from_string("(1, 2, 3.14)")})
assert.same({v, 12}, {vector.from_string("(1,2 ,3.14)")})
assert.same({v, 12}, {vector.from_string("(1,2,3.14,)")})
assert.same({v, 11}, {vector.from_string("(1 2 3.14)")})
assert.same({v, 15}, {vector.from_string("( 1, 2, 3.14 )")})
assert.same({v, 15}, {vector.from_string(" ( 1, 2, 3.14) ")})
assert.same({vector.new(), 8}, {vector.from_string("(0,0,0) ( 1, 2, 3.14) ")})
assert.same({v, 22}, {vector.from_string("(0,0,0) ( 1, 2, 3.14) ", 8)})
assert.same({v, 22}, {vector.from_string("(0,0,0) ( 1, 2, 3.14) ", 9)})
assert.same(nil, vector.from_string("nothing"))
end)

-- This function is needed because of floating point imprecision.
local function almost_equal(a, b)
if type(a) == "number" then
@@ -12,6 +12,22 @@ function vector.new(a, b, c)
return {x=0, y=0, z=0}
end

function vector.from_string(s, init)
local x, y, z, np = string.match(s, "^%s*%(%s*([^%s,]+)%s*[,%s]%s*([^%s,]+)%s*[,%s]" ..
"%s*([^%s,]+)%s*[,%s]?%s*%)()", init)
x = tonumber(x)
y = tonumber(y)
z = tonumber(z)
if not (x and y and z) then
return nil
end
return {x = x, y = y, z = z}, np
end

function vector.to_string(v)
return string.format("(%g, %g, %g)", v.x, v.y, v.z)
end

function vector.equals(a, b)
return a.x == b.x and
a.y == b.y and
@@ -3149,6 +3149,16 @@ For the following functions, `v`, `v1`, `v2` are vectors,
* Returns a vector.
* A copy of `a` if `a` is a vector.
* `{x = a, y = b, z = c}`, if all of `a`, `b`, `c` are defined numbers.
* `vector.from_string(s[, init])`:
* Returns `v, np`, where `v` is a vector read from the given string `s` and
`np` is the next position in the string after the vector.
* Returns `nil` on failure.
* `s`: Has to begin with a substring of the form `"(x, y, z)"`. Additional
spaces, leaving away commas and adding an additional comma to the end
is allowed.
* `init`: If given starts looking for the vector at this string index.
* `vector.to_string(v)`:
* Returns a string of the form `"(x, y, z)"`.
* `vector.direction(p1, p2)`:
* Returns a vector of length 1 with direction `p1` to `p2`.
* If `p1` and `p2` are identical, returns `{x = 0, y = 0, z = 0}`.

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