Behavior of `isNumber`

:

```
str="7"
a=isNumber(str)
b=isNumber(+str)
Return(a,b)
```

Result: a=0, b=1

So, if one wants to extract numbers from a string, one has to use the unary “+” for testing, wether the string (or part of) is numeric.

But unfortunately this test goes wrong in case of a not numeric string:

```
str="some string"
a=isNumber(str)
b=isNumber(+str)
Return(a,b)
```

Result: `a=0, b=1`

So: `isNumber(+"Hello world")`

returns 1 …

A variant of `isNumber`

works better:

```
str="7"
a=0
b=0
if str is Number
a=1
end
if +str is Number
b=1
end
Return(a, b)
```

Result: `a=1, b=1`

But …

```
str="some string"
a=0
b=0
if str is Number
a=1
end
if +str is Number
b=1
end
Return(a, b)
```

Result: `a=1, b=0`

So the test of a numeric part in a string works correct, if one uses the construction “if … is Number” with unary +.

Things would be simpler and clearer if the expression `isNumber(+"some string")`

would return 0 instead of 1.

Fix in one of the next releases?