fmt.Println不会打印整个浮点数

Question

i'm trying to make a program that calculates the value of pi and print it on the terminal, but only part of it shows on the screen

package main

import (
    "fmt"
)

func gregorypi() float64 {
    numerator := 1.0
    divisor := 3.0
    var result float64

    for i := 0; i <= 100000000; i++ {
            if i%2 == 0 {
                    result += numerator / divisor
                    divisor += 2
            } else {
                    result -= numerator / divisor
                    divisor += 2

            }

    }

    return (4 * (1 - result))

}

func main() {

    fmt.Sprint(gregorypi())

}

the output is: 3.1415926435897683

How do i make so the entire value appears?

If it helps answering the question: the formula that i'm using is the Gregory-Leibniz one

Answer 1

func Sprint

func Sprint(a ...interface{}) string

Sprint formats using the default formats for its operands and returns the resulting string. Spaces are added between operands when neither is a string.

---

fmt.Sprint returns a string. Don't throw it away; print it.

For example,

func main() {
    s := fmt.Sprint(gregorypi())
    fmt.Println(s)
}

Playground: https://play.golang.org/p/zOVtJc5HfXT

Output:

3.1415926435897683

---

If you want a more precise result than IEEE 754 64-bit floating-point, use the Go math/big package.

---

For example,

package main

import (
    "fmt"
    "math/big"
)

func gregorypi(iter int, prec uint) *big.Float {
    one := big.NewFloat(1)
    two := big.NewFloat(2)
    four := big.NewFloat(4)
    numerator := big.NewFloat(1).SetPrec(prec)
    divisor := big.NewFloat(3).SetPrec(prec)
    result := new(big.Float).SetPrec(prec)

    for i := 0; i <= iter; i++ {
        if i%2 == 0 {
            result.Add(result, new(big.Float).Quo(numerator, divisor))
        } else {
            result.Sub(result, new(big.Float).Quo(numerator, divisor))
        }
        divisor.Add(divisor, two)
    }

    return new(big.Float).Mul(four, (new(big.Float).Sub(one, result)))

}

func main() {
    pi := gregorypi(1000000, 4096)

    s := fmt.Sprint(pi)
    for i, j := 0, 0; i < len(s); i = j {
        j = i + 60
        if j > len(s) {
            j = len(s)
        }
        fmt.Println(s[i:j])
    }
}

Output:

3.1415916535917932347126498832691903993221476025342620143148
652250543253683419302770934570540444696092784515646197918416
151531004207388567190381995115109764938931650751911723670828
705935671760975424757204401786734958287682330276123443546400
855990841037108771486255447137253791363986086026524209725177
041621398938122502069099548344075841960714856836014332632487
249750055949826053894250927777836988620276187954914335474236
918693730264540456485214156731536507281567237095178205850787
841887779856892311307656085287982909183503886914799719930651
362811646060939082163336282527001630768619465916054216662233
647867947277285894357821722722774052560440050583160360321106
944441543917458948854721791262992799982426130041196627951982
504267630916391384654303083557011574782570253034162966525670
594481466474403221843818413155653700689258246423537757630787
951957260253561222183715232613769610553278998905210089847178
951692922815021787390361813556619177840043555176857090268624
902791212304201317960964869615176784400855500998688041903616
187746299057333789390884081442894661717258714989758581139759
403617872623424695182488545758897457727485849932980050101014
208290473579625783313281627594640164541223264510142763045401
708614153731722941036904397534247