PHP: gmp_init - Manual (original) (raw)

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

gmp_init — Create GMP number

Description

Parameters

num

An integer or a string. The string representation can be decimal, hexadecimal, octal, or binary.

base

The base to use for converting a string representation. An explicit base can be between 2 and 62. For bases up to 36, case is ignored; upper-case and lower-case letters have the same value. For bases 37 to 62, upper-case letter represent the values 10 to35 and lower-case letter represent the values36 to 61. If base is 0 then the actual base is determined from the leading characters of num. If the first two characters are 0x or 0X, the string is interpreted as a hexadecimal integer. If the first two characters are 0b or 0B, the string is interpreted as a binary integer. If the first two characters are 0o or 0o, the string is interpreted as an octal integer. Moreover, if the first character is 0 the string is also interpreted as an octal integer. In all other cases, the string is interpreted as a decimal integer.

Return Values

A GMP object.

Changelog

Version	Description
8.1.0	Support for explicit octal prefixes 0o and0o has been added for num strings. Interpretation of such prefixes when base is0 has also been added.

Examples

Example #1 Creating GMP number

<?php $a = gmp_init(123456); $b = gmp_init("0xFFFFDEBACDFEDF7200"); ?>

Notes

Note:

It is not necessary to call this function in order to use integers or strings in place of GMP numbers in GMP functions (such as withgmp_add()). Function arguments are automatically converted to GMP numbers, if such conversion is possible and needed, using the same rules as gmp_init().

Found A Problem?

php at richardneill dot org ¶

19 years ago

Here's a way to parse a decimal (eg 3.25) into an integer and exponent:

<?
if (preg_match("/^[0-9]+\.[0-9]+$/",$input)){ 
     //Input is a base-10 decimal. Multiply as necessary to remove the decimal
     //point. Convert that to a gmp_resource, then decrement the exponent 
     //to compensate.

     <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>p</mi><mi>i</mi><mi>e</mi><mi>c</mi><mi>e</mi><mi>s</mi><mo>=</mo><mi>e</mi><mi>x</mi><mi>p</mi><mi>l</mi><mi>o</mi><mi>d</mi><mi>e</mi><mo stretchy="false">(</mo><mi mathvariant="normal">&quot;</mi><mi mathvariant="normal">.</mi><mi mathvariant="normal">&quot;</mi><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">pieces=explode(&quot;.&quot;, </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.854em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">p</span><span class="mord mathnormal">i</span><span class="mord mathnormal">eces</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">e</span><span class="mord mathnormal">x</span><span class="mord mathnormal" style="margin-right:0.01968em;">pl</span><span class="mord mathnormal">o</span><span class="mord mathnormal">d</span><span class="mord mathnormal">e</span><span class="mopen">(</span><span class="mord">&quot;.&quot;</span><span class="mpunct">,</span></span></span></span>input);     //Split at the d.p.
     <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>i</mi><mi>n</mi><mi>p</mi><mi>u</mi><mi>t</mi><mo>=</mo><mi mathvariant="normal">&quot;</mi></mrow><annotation encoding="application/x-tex">input=&quot;</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.854em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">in</span><span class="mord mathnormal">p</span><span class="mord mathnormal">u</span><span class="mord mathnormal">t</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord">&quot;</span></span></span></span>pieces[0]$pieces[1]";  //Remove the decimal point.

     <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>i</mi><mi>n</mi><mi>p</mi><mi>u</mi><mi>t</mi><mo>=</mo><mi>l</mi><mi>t</mi><mi>r</mi><mi>i</mi><mi>m</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">input=ltrim(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.854em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">in</span><span class="mord mathnormal">p</span><span class="mord mathnormal">u</span><span class="mord mathnormal">t</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">lt</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mord mathnormal">im</span><span class="mopen">(</span></span></span></span>input,'0');    
     //Remove any leading zeros, or gmp_init will parse the number as octal.

     if ($input==''){    //Deal with "0.0" which would otherwise be ''.
          $input=0;
      }
      <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>i</mi><mi>n</mi><mi>t</mi><mi>e</mi><mi>g</mi><mi>e</mi><mi>r</mi><mo>=</mo><mi>g</mi><mi>m</mi><msub><mi>p</mi><mi>i</mi></msub><mi>n</mi><mi>i</mi><mi>t</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">integer=gmp_init(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.854em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">in</span><span class="mord mathnormal">t</span><span class="mord mathnormal">e</span><span class="mord mathnormal" style="margin-right:0.03588em;">g</span><span class="mord mathnormal" style="margin-right:0.02778em;">er</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">g</span><span class="mord mathnormal">m</span><span class="mord"><span class="mord mathnormal">p</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.3117em;"><span style="top:-2.55em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">i</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord mathnormal">ni</span><span class="mord mathnormal">t</span><span class="mopen">(</span></span></span></span>input);   
      <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>n</mi><msub><mi>s</mi><mi>e</mi></msub><mi>x</mi><mi>p</mi><mi>o</mi><mi>n</mi><mi>e</mi><mi>n</mi><mi>t</mi><mo>=</mo><mo>−</mo><mi>s</mi><mi>t</mi><mi>r</mi><mi>l</mi><mi>e</mi><mi>n</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">ns_exponent=-strlen(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8095em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">n</span><span class="mord"><span class="mord mathnormal">s</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.1514em;"><span style="top:-2.55em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">e</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord mathnormal">x</span><span class="mord mathnormal">p</span><span class="mord mathnormal">o</span><span class="mord mathnormal">n</span><span class="mord mathnormal">e</span><span class="mord mathnormal">n</span><span class="mord mathnormal">t</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord">−</span><span class="mord mathnormal">s</span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">e</span><span class="mord mathnormal">n</span><span class="mopen">(</span></span></span></span>pieces[1]);  
     //exponent = (-)  the number of characters after the decimal point.
}
?>

karl dot debisschop at pearson dot com ¶

14 years ago

Unless the base is 16, gpm_init will fail if the string begins with "0b". 

> php -r '$v = gmp_init("b83", 17); print("$v\n");'

Resource id #4

> php -r '$v = gmp_init("0b83", 17); print("$v\n");'

[nothing prints]

In may case, where I am explicitly specifying the base, the solution is to apply ltrim first:

> php -r '$v = gmp_init(ltrim("0b83", "0"), 17); print("$v\n");'

Resource id #4

marcus at synchromedia dot co dot uk ¶

14 years ago

I discovered that the gmp functions use [0-9a-f] up to base 16, but [0-9A-Za-z] (i.e. upper case first) from bases 17 to 62. This differs from most of the base-62 implementations I've found that tend to use lower case first.

Aurelien Marchand ¶

3 years ago

Missing from the documentation: gmp_init() return false in case it failed to parse $num

<?php
var_dump(gmp_init(""));
// returns "bool(false)" and not a GMP object as hinted by the documentation, it also triggers a Warning "PHP Warning:  gmp_init(): Unable to convert variable to GMP - string is not an integer in php shell code on line 1"

?>

charlie at oblivion dot cz ¶

18 years ago

gmp_* functions don't accept strings with a leading '+':
<?php
echo gmp_strval(gmp_init('+42'));      #0
echo gmp_strval(gmp_add('42', '+42')); #42
echo bcadd('+42', '+42');              #84
?>

php at richardneill dot org ¶

19 years ago

Note: Leading zeros will make gmp_init parse this as octal.
Thus gmp_init(010) becomes 8.  

$a=010;              //8
$b="010" + 0;     //10
$c=gmp_strval(gmp_init(010));    //8
$d=gmp_strval(gmp_init("010")); //8

This behaviour is inconsistent: either <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>d</mi><mi>s</mi><mi>h</mi><mi>o</mi><mi>u</mi><mi>l</mi><mi>d</mi><mi>e</mi><mi>q</mi><mi>u</mi><mi>a</mi><mi>l</mi></mrow><annotation encoding="application/x-tex">d should equal </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">d</span><span class="mord mathnormal">s</span><span class="mord mathnormal">h</span><span class="mord mathnormal">o</span><span class="mord mathnormal">u</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">d</span><span class="mord mathnormal">e</span><span class="mord mathnormal" style="margin-right:0.03588em;">q</span><span class="mord mathnormal">u</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span></span></span></span>b, or <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>b</mi><mi>s</mi><mi>h</mi><mi>o</mi><mi>u</mi><mi>l</mi><mi>d</mi><mi>e</mi><mi>q</mi><mi>u</mi><mi>a</mi><mi>l</mi></mrow><annotation encoding="application/x-tex">b should equal </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">b</span><span class="mord mathnormal">s</span><span class="mord mathnormal">h</span><span class="mord mathnormal">o</span><span class="mord mathnormal">u</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">d</span><span class="mord mathnormal">e</span><span class="mord mathnormal" style="margin-right:0.03588em;">q</span><span class="mord mathnormal">u</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span></span></span></span>a.

thomas dot hebinck at digionline dot de ¶

20 years ago

If you call a gmp_* function directly with an interger as parameter, this integer MUST NOT be 0:

for($i=-1;$i<=1;$i++) {  echo gmp_strval(gmp_add(2,gmp_mul(1,$i))) . ' ';  }

The result is 1 0 3 (wrong)

In this case you have to use gmp_init():

for($i=-1;$i<=1;$i++) {  echo gmp_strval(gmp_add(2,gmp_mul(1,gmp_init($i)))) . ' ';  }

The result is 1 2 3 (right)

Happy number crunching! :-)