Talk:Determine if a string is numeric: Difference between revisions
Talk:Determine if a string is numeric (view source)
Revision as of 17:45, 15 September 2021
, 2 years ago→Assembly implementation is harder than I thought
(→Exact definition of IsNumeric?: added comments about leading signs. -- ~~~~) |
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For those who don't know VB: How exactly is IsNumeric defined?
For example: Is leading/trailing whitespace allowed (i.e. " 123" or "123 ")?
Does it also accept
What about thousands separators (e.g. "10,000")? Is that locale-dependent?
Are numbers in other bases (e.g. hexadecimal) allowed (assuming VB supports them otherwise)?
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The IsNumeric call will not always return a correct answer. Try "1234+" - IsNumeric will return True. Then pass this same value as an argument to Convert.ToDouble: it will fail "unhandled exception". There's no option but to loop thru the String character by character and check that each one is within range. --[[User:LazyZee|LazyZee]] 17:59, 19 October 2012 (UTC)
== R ==
The solution will not work correctly if the string contains "NA" (not a number). But NA can be used in numeric calculations. --[[User:Sigbert|Sigbert]] ([[User talk:Sigbert|talk]]) 13:01, 16 February 2015 (UTC)
== AWK code is wrong ==
<pre>
awk 'BEGIN { x = "01"; print x == x+0 }'
0
awk 'BEGIN { x = "+1"; print x == x+0 }'
0
awk 'BEGIN { x = "1x"; print x == x+0 }'
0
</pre>
But
<pre>
awk 'BEGIN { x = "1x"; print x+1 }'
2
</pre>
== Assembly implementation is harder than I thought==
The way I see it, the code will need to do the following:
Read the first character.
* If it's a null terminator, the program ends and the string is not numeric.
* If it's a minus sign, that's valid and so we can continue
* If it's a decimal point, that's valid and we can continue. However, the presence of a decimal point must be recorded. If the string contains a second decimal point it stops being numeric.
* If it's not a number, at this point the string is not numeric. Otherwise continue.
Read the second character.
* If it's the terminator, the string is numeric if the first character was a numeral. If the first character was a minus sign or decimal point, the string is not numeric.
* If the second character is a numeral, continue.
* If the second character is a decimal point, continue if we haven't seen one already. If there is more than one decimal point the string is not numeric.
* If the second character is anything else, the string is not numeric.
Loop through the rest of the string.
* If we encounter the terminator, the string is numeric.
* If we encounter a numeral, continue.
* If we encounter a second decimal point, the string is not numeric.
* If we encounter anything besides a numeral, the null terminator, or the first occurrence of a decimal point, the string is not numeric.
I've attempted this in both 8086 and z80 but it ends up looking like spaghetti no matter what I do.
: @[[User: Puppydrum64]]: Uhm, is this task even applicable for assembly? I don’t thinks so. You know, depending on the assembler used there are ''several'' ways to write numeric literals. In NASM, for instance, I can write <tt>0b0110_1101</tt>. There simply isn’t ''a/the'' programming language “8086 assembly” ''defining'' how to write numeric literals. What you are attempting to do, though, is rather writing an assembly function that accepts a null-terminated string that represents a valid numeric literal ''in C'' (and many ''other'' programming languages), but not “8086 assembly”, you know what I mean? [[User:Root|Root]] ([[User talk:Root|talk]]) 18:10, 20 August 2021 (UTC)
I get what you mean. I figured at least attempting something that represents a valid numeric literal in higher-level languages was as close as I could get. Throwing in the towel and just saying "This is assembly, there are no rules" would disqualify it from almost everything. --[[User:Puppydrum64|Puppydrum64]] ([[User talk:Puppydrum64|talk]]) 17:45, 15 September 2021 (UTC)
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