Lua arithmetic on string variable

Question

I have this small snippet of code here;

for i=1,1000 do
    n=math.floor(math.sin(i/10.0)*40)
    s=''
    for j=1,n do s=s+'-' end
    print(s)
end

But it gives me an error on line 2: "attempt to perform arithmetic on global 's' (a string value)" I don't know why it's doing this, and it's driving me mad.

Use string.rep instead of the inner for.

lhf
– lhf

2014-09-26 12:57:56 +00:00
Commented Sep 26, 2014 at 12:57 — lhf
– lhf, Commented Sep 26, 2014 at 12:57

Yu Hao · Accepted Answer · 2014-09-26 12:48:49Z

4

Unlike some other languages, Lua uses .. to concatenate strings, not +, change

s = s + '-'

to

s = s .. '-'

answered Sep 26, 2014 at 12:48

Yu Hao

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Comments

lhf · Accepted Answer · 2014-09-26 14:38:00Z

1

A loop of string concatenations is not recommended because it leads to a quadratic copy (not that it matters for small strings). Try string.rep instead.

for i=1,1000 do
    n=math.floor(math.sin(i/10.0)*40)
    print(string.rep('-',n))
end

answered Sep 26, 2014 at 14:38

lhf

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