IsNumeric

[Resike]

I need a function which iterates in a string and determines if it's only containts numeric characters, or not.

Nevermind i had a better idea:

function isNumeric(value)
if value == tostring(tonumber(value)) then
    return true
else
    return false
end
end

[zork]

tonumber(val)

if tonumber(val) then print("OK") end

strmatch(val,pattern)

if strmatch(val,"%d") then print("OK") end

--list %a --- represents all letters. %c --- represents all control characters. %d --- represents all digits. %l --- represents all lowercase letters. %p --- represents all punctuation characters. %s --- represents all space characters. %u --- represents all uppercase letters. %w --- represents all alphanumeric characters. %x --- represents all hexadecimal digits. %z --- represents the character with representation 0.

[Billtopia]

I was thinking that this may be better for you but not 100% the pattern is right. It should find any decimal number including decimals with a decimal portion and if that is the only thing on the line (not counting white spaces) then return true

function IsNumeric( data )
    if type(data) == "number" then
        return true
    elseif type(data) ~= "string" then
        return false
    end
    data = strtrim(data)
    local x, y = string.find(data, "[%d+][%.?][%d*]")
    if x and x == 1 and y == strlen(data) then
        return true
    end
    return false
end

[Resike]

Originally Posted by zork tonumber(val) if tonumber(val) then print("OK") end strmatch(val,pattern) if strmatch(val,"%d") then print("OK") end

I don't think the first one would work, because it's converting letters "1234a" -> 1234.

The second one could work with decimals, but would fail on floats and "+", "-" values.

[Resike]

Originally Posted by Billtopia I was thinking that this may be better for you but not 100% the pattern is right. It should find any decimal number including decimals with a decimal portion and if that is the only thing on the line (not counting white spaces) then return true function IsNumeric( data )     if type(data) == "number" then         return true     elseif type(data) ~= "string" then         return false     end     data = strtrim(data)     local x, y = string.find(data, "[%d+][%.?][%d*]")     if x and x == 1 and y == strlen(data) then         return true     end     return false end

Hmm thats seems good, but i think it's slower then my method.

[Billtopia]

well you did say that you wanted to know if they passed only numbers... converting to a number from the string will convert what (if anything) it can, not test for non numbers included as well

[Resike]

Originally Posted by Billtopia well you did say that you wanted to know if they passed only numbers... converting to a number from the string will convert what (if anything) it can, not test for non numbers included as well

Yes but i compare that value back to the original one:

value == tostring(tonumber(value))

"1234" string -> converts to 1234 number converts back to "1234" string. (Equal.)

"1234a" string -> converts to 1234 number converts back to "1234" string. (Not equal!)

"-12.34" string -> converts to -12.34 number converts back to "-12.24" string. (Equal.)

"-12.34a" string -> converts to -12.34 number converts badk to "-12.34" string (Not equal.)

[Phanx]

How about:

if strmatch(str, "^%-?[%d%.]+%d$") then print("OK") end

Will match "-2.5" and "-2" and"-.5" and ".5" and "2.5" but not "25." or "2-5" or "25-"

[Haleth]

Edit: I'm not a wise man.

[Clamsoda]

tostring() and tonumber() are largely useless in Lua, correct? Lua automatically interprets numbers as numbers or strings depending on the operation.

(Would love input though.)

[Haleth]

Originally Posted by Clamsoda tostring() and tonumber() are largely useless in Lua, correct? Lua automatically interprets numbers as numbers or strings depending on the operation. (Would love input though.)

tonumber() is used for validation (such as in this situation). Not too sure on tostring().

Also, that reminds me:

I don't think the first one would work, because it's converting letters "1234a" -> 1234.

tonumber() doesn't actually do that. It would just return nil, it doesn't drop characters from strings.

[Vrul]

Originally Posted by Haleth I don't think you need to use tostring in your updated OP. Lua will automatically convert number to string in comparisons.

This is false. The comparison 5 == "5" will evaluate as false as it should. The comparison 5 < "8" will throw an error.

Originally Posted by Clamsoda tostring() and tonumber() are largely useless in Lua, correct? Lua automatically interprets numbers as numbers or strings depending on the operation.

Lua will automatically convert a number to a string, or string to a number, in some cases (e.g. addition, concatenation) but not all (e.g. comparisons).

[Haleth]

Huh. I must've been confusing it with another language - now I need to go back and double check some code I wrote recently my bad.

[Clamsoda]

Oh I see. I never considered the comparison situation, but I knew for the others. Always piqued my interest when I saw code making a useless tonumber() call.

Thank you for the clarification!

[Resike]

Originally Posted by Haleth tonumber() doesn't actually do that. It would just return nil, it doesn't drop characters from strings.

You might be right, some other language do that tho.

[Torhal]

Originally Posted by Resike You might be right, some other language do that tho.

He's right.

[Phanx]

Aside from the techinical implementations, you should probably take a hard look at your code and figure out why you're needing to double-check the type of a value like this in the first place.