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Date: Mon, 28 Jul 2025 15:00:52 +0200
Message-ID: <CAMU7irLRxzscESjV2XxG4r9S5U4cQ+bpZZO+pKofm-LsVQvpHg@mail.gmail.com>
Subject: Re: [PHP-DEV] [DISCUSSION] Adding the "is_integer_safe()" function
To: "Gina P. Banyard" <internals@gpb.moe>
Cc: PHP internals list <internals@lists.php.net>
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From: alex.daubois+php@gmail.com (Alexandre Daubois)

Le lun. 28 juil. 2025 =C3=A0 12:14, Gina P. Banyard <internals@gpb.moe> a =
=C3=A9crit :
> For naming, maybe the following pair of functions make sense?
> - is_representable_as_int()

Definitely, thank you for proposing. Having a pair of functions for
bidirectional transformations makes much more sense than a single
ambiguous function. Here are some quick specs for what these functions
could do.

`is_representable_as_int(mixed $value): bool` checks if a given value
can be losslessly converted to an integer.

- Floats: returns true if the float is within PHP_INT_MIN to
PHP_INT_MAX range AND has no fractional part
- Strings: returns true if the string represents a valid integer
within the platform's integer range
- Always returns true for integers
- Special float values: returns false for NaN, INF, -INF

This gives the following example:

```php
is_representable_as_int(42.0);        // true
is_representable_as_int(42.5);        // false
is_representable_as_int(2**31);       // false on 32-bit, true on 64-bit
is_representable_as_int(2**63);       // false on both platforms
is_representable_as_int("123");       // true
is_representable_as_int("123.0");     // true
is_representable_as_int("123.5");     // false
is_representable_as_int(NAN);         // false
```

> - is_representable_as_float()

Now, `is_representable_as_float(mixed $value): bool`. The function
would check if a value can be represented as a float without precision
loss.

- Integers: returns true if within the IEEE 754 safe integer range
(+/-(2^53-1)) regardless of the system's PHP_INT_MAX
- Strings: returns true if parseable as a float within safe precision bound=
s
- Floats always returns true
- The IEEE 754 safe integer limit applies universally

This give the following examples:

```php
is_representable_as_float(2**53 - 1); // true
is_representable_as_float(2**53);     // false, precision loss when
casted to float
is_representable_as_float(PHP_INT_MAX); // false on 64-bit, true on 32-bit
is_representable_as_float(42);        // true
is_representable_as_float("123.456"); // true
is_representable_as_float("1e308");   // true
is_representable_as_float("1e400");   // false
```

What do you think of this new approach?

Best,
Alexandre Daubois