[PHP知识库]php数学函数，加（bcadd）、减（bcsub）、乘（bcmul）、除（bcdiv）

bcscale() 来设置全局默认的小数位数

bcscale ( int $scale ) : bool

设置所有bc数学函数的未设定情况下得小数点保留位数.

bcadd — 2个任意精度数字的加法计算

左操作数和右操作数求和 ,scale 用于设置结果中小数点后的小数位数。

bcadd ( string $left_operand , string $right_operand [, int $scale ] ) : string

<?php
$a?=?'1.234';
$b?=?'5';
????echo?bcadd($a,?$b);?????//?6
????echo?bcadd($a,?$b,?4);??//?6.2340
?>

bccomp?—?比较两个任意精度的数字

bccomp?(?string?$left_operand?,?string?$right_operand?[,?int?$scale?= int?] ) :?int

<?phpecho?bccomp('1',?'2')?.?"\n";???//?-1
????echo?bccomp('1.00001',?'1',?3);?//?0
????echo?bccomp('1.00001',?'1',?5);?//?1
?>

bcdiv?—?2个任意精度的数字除法计算

bcdiv?(?string?$left_operand?,?string?$right_operand?[,?int?$scale?= int?] ) :?string

<?php
//?default?scale?:?3
????bcscale(3);
????echo?bcdiv('105',?'6.55957');?//?16.007
//?this?is?the?same?without?bcscale()
????echo?bcdiv('105',?'6.55957',?3);?//?16.007
?>

bcmod?—?对一个任意精度数字取模

bcmod?(?string?$left_operand?,?string?$modulus?) :?string

<?php
????echo?bcmod('4',?'2');?//?0
????echo?bcmod('2',?'4');?//?2
?>

bcmul?—?2个任意精度数字乘法计算

bcmul?(?string?$left_operand?,?string?$right_operand?[,?int?$scale?= int?] ) :?string

<?php
????echo?bcmul('1.34747474747',?'35',?3);?//?47.161
????echo?bcmul('2',?'4');?//?8
?>

bcpow?—?任意精度数字的乘方

bcpow?(?string?$left_operand?,?string?$right_operand?[,?int?$scale?] ) :?string

<?php
????echo?bcpow('4.2',?'3',?2);?//?74.08
?>

bcpowmod----将任意的精确数提高到另一个，再用指定的模量还原

bcpowmod?(?string?$base?,?string?$exponent?,?string?$modulus?[,?int?$scale?= 0?] ) :?string

<?php
????$a?=?bcpowmod($x,?$y,?$mod);
????$b?=?bcmod(bcpow($x,?$y),?$mod);//?
????$a?and?$b?are?equal?to?each?other.
?>

bcscale?—?设置所有bc数学函数的默认小数点保留位数

bcscale?(?int?$scale?) :?bool

bcsqrt?—?任意精度数字的二次方根

bcsqrt?(?string?$operand?[,?int?$scale?] ) :?string

<?php
????echo?bcsqrt('2',?3);?//?1.414
?>

bcsub?—?2个任意精度数字的减法

bcsub?(?string?$left_operand?,?string?$right_operand?[,?int?$scale?= int?] ) :?string