- added ParseComplex function

Author: pjebs

src/strconv/atoc.go

@@ -0,0 +1,155 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv
+
+func convErr(err error, s string) error {
+	if x, ok := err.(*NumError); ok {
+		x.Func = fnParseComplex
+		x.Num = s
+	}
+	return err
+}
+
+func parseFloat(s, orig string, bitSize int) (float64, error) {
+	if bitSize == 64 {
+		f, err := ParseFloat(s, 32)
+		if err != nil {
+			return 0, convErr(err, orig)
+		}
+		return f, nil
+	}
+
+	f, err := ParseFloat(s, 64)
+	if err != nil {
+		return 0, convErr(err, orig)
+	}
+	return f, nil
+}
+
+const fnParseComplex = "ParseComplex"
+
+// ParseComplex converts the string s to a complex number
+// with the precision specified by bitSize: 64 for complex64, or 128 for complex128.
+// When bitSize=64, the result still has type complex128, but it will be
+// convertible to complex64 without changing its value.
+//
+// The number represented by s may or may not be parenthesized and have the format (N+Ni) where N is
+// a floating-point number. There must not be spaces between the real and imaginary components.
+//
+// ParseComplex accepts decimal and hexadecimal floating-point number syntax.
+// If s is well-formed and near a valid floating-point number,
+// ParseComplex returns the nearest floating-point number rounded
+// using IEEE754 unbiased rounding.
+// (Parsing a hexadecimal floating-point value only rounds when
+// there are more bits in the hexadecimal representation than
+// will fit in the mantissa.)
+//
+// The errors that ParseComplex returns have concrete type *NumError
+// and include err.Num = s.
+//
+// If s is not syntactically well-formed, ParseComplex returns err.Err = ErrSyntax.
+//
+// If s is syntactically well-formed but is more than 1/2 ULP
+// away from the largest floating point number of the given size,
+// ParseComplex returns f = ±Inf, err.Err = ErrRange.
+//
+// ParseComplex recognizes the strings "NaN", "+Inf", and "-Inf" as their
+// respective special floating point values for each component. It ignores case when matching.
+func ParseComplex(s string, bitSize int) (complex128, error) {
+
+	orig := s
+
+	if len(s) == 0 {
+		return 0, syntaxError(fnParseComplex, orig)
+	}
+
+	lastChar := s[len(s)-1 : len(s)]
+
+	// Remove brackets
+	if len(s) > 1 && s[0:1] == "(" && lastChar == ")" {
+		s = s[1 : len(s)-1]
+		lastChar = s[len(s)-1 : len(s)]
+	}
+
+	// Is last character an i?
+	if lastChar != "i" {
+		// The last character is not an i so there is only a real component.
+		real, err := parseFloat(s, orig, bitSize)
+		if err != nil {
+			return 0, err
+		}
+		return complex(real, 0), nil
+	}
+
+	// Remove last char which is an i
+	s = s[0 : len(s)-1]
+
+	// Count how many ± exist.
+	pos := []int{}
+
+	for idx, rune := range s {
+		if rune == '+' || rune == '-' {
+			pos = append(pos, idx)
+		}
+	}
+
+	if len(pos) == 0 {
+		// There is only an imaginary component
+
+		if s == "" {
+			s = "1"
+		}
+
+		imag, err := parseFloat(s, orig, bitSize)
+		if err != nil {
+			return 0, err
+		}
+		return complex(0, imag), nil
+
+	} else if len(pos) > 4 {
+		// Too many ± exists for a valid complex number
+		return 0, syntaxError(fnParseComplex, orig)
+	}
+
+	/* From here onwards, it is either complex number with both a real and imaginary component OR a pure imaginary number in exponential form. */
+
+	// Loop through pos from middle of slice, outwards
+	mid := (len(pos) - 1) >> 1
+	for j := 0; j < len(pos); j++ {
+		var idx int
+		if j%2 == 0 {
+			idx = mid - j/2
+		} else {
+			idx = mid + (j/2 + 1)
+		}
+
+		left := s[0:pos[idx]]
+		right := s[pos[idx]:]
+
+		// Check if left and right are valid float64
+		real, err := parseFloat(left, orig, bitSize)
+		if err != nil {
+			continue
+		}
+
+		if right == "+" || right == "-" {
+			right = right + "1"
+		}
+
+		imag, err := parseFloat(right, orig, bitSize)
+		if err != nil {
+			continue
+		}
+
+		return complex(real, imag), nil
+	}
+
+	// Pure imaginary number in exponential form
+	imag, err := parseFloat(s, orig, bitSize)
+	if err != nil {
+		return 0, err
+	}
+	return complex(0, imag), nil
+}

src/strconv/atoc_test.go

@@ -0,0 +1,17 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strconv_test
+
+import ()
+
+// Test cases required:
+// hex form
+// exp form
+// Only real
+// Only imag
+// Both real and imag
+// With and without parentheses
+// NaN
+// ±Inf

src/strconv/atof.go

@@ -678,7 +678,3 @@ func ParseFloat(s string, bitSize int) (float64, error) {
 	}
 	return atof64(s)
 }
-
-func ParseComplex(s string, bitSize int) (float64, error) {
-	return 0,nil	
-}