Talk:Determine if a string is numeric

Unix shell

#!/bin/sh

a='123'
if [ "$a" -eq "$a" ] 2>/dev/null
then
    echo "a is numeric"
else
    echo "a is abnumeric"
fi

Exact definition of IsNumeric?

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 floting point values (e.g. "2.5" or "1e5")? 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)? What about numbers too big to fit into a native integer (e.g. "9999999999999999999999999999999999999999999999999") resp. a native float (e.g. "1e1234567")?

And what is its input? The Python and C samples take a string. The Ruby and Scheme samples take an object. And in Tcl it's the same thing.

Half the samples shown implement 'is integer', or 'is numeric character'.

In VB, IsNumeric is a function for validating input. VB examples (all true)

1, 1.1, -1.1, "1", "1.1", "-1.1" "1.1-", " 1.1- ", " 1,1 ", " 1E1" "&HFF"

VBscript:

msgbox isnumeric(1)

msgbox isnumeric(1.1)

msgbox isnumeric(-1.1)

msgbox isnumeric("1")

msgbox isnumeric( "1.1")

msgbox isnumeric( "-1.1")

msgbox isnumeric( " 1.1- ")

msgbox isnumeric(" 1,1 ")

msgbox isnumeric(" 1E1 ")

msgbox isnumeric(" &HFF ")