ctoa.go

     1  // Copyright 2020 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package strconv
     6  
     7  // FormatComplex converts the complex number c to a string of the
     8  // form (a+bi) where a and b are the real and imaginary parts,
     9  // formatted according to the format fmt and precision prec.
    10  //
    11  // The format fmt and precision prec have the same meaning as in [FormatFloat].
    12  // It rounds the result assuming that the original was obtained from a complex
    13  // value of bitSize bits, which must be 64 for complex64 and 128 for complex128.
    14  func FormatComplex(c complex128, fmt byte, prec, bitSize int) string {
    15  	var buf [64]byte
    16  	return string(AppendComplex(buf[:0], c, fmt, prec, bitSize))
    17  }
    18  
    19  // AppendComplex appends the result of FormatComplex to dst.
    20  // It is here for the runtime.
    21  // There is no public strconv.AppendComplex.
    22  func AppendComplex(dst []byte, c complex128, fmt byte, prec, bitSize int) []byte {
    23  	if bitSize != 64 && bitSize != 128 {
    24  		panic("invalid bitSize")
    25  	}
    26  	bitSize >>= 1 // complex64 uses float32 internally
    27  
    28  	dst = append(dst, '(')
    29  	dst = AppendFloat(dst, real(c), fmt, prec, bitSize)
    30  	i := len(dst)
    31  	dst = AppendFloat(dst, imag(c), fmt, prec, bitSize)
    32  	// Check if imaginary part has a sign. If not, add one.
    33  	if dst[i] != '+' && dst[i] != '-' {
    34  		dst = append(dst, 0)
    35  		copy(dst[i+1:], dst[i:])
    36  		dst[i] = '+'
    37  	}
    38  	dst = append(dst, "i)"...)
    39  	return dst
    40  }
    41
View as plain text