diff --git a/src/pkg/strconv/ftoa.go b/src/pkg/strconv/ftoa.go index 656d81c981..3659243c79 100644 --- a/src/pkg/strconv/ftoa.go +++ b/src/pkg/strconv/ftoa.go @@ -154,21 +154,27 @@ func genericFtoa(bits uint64, fmt byte, prec int, flt *floatInfo) string { case 'f': return fmtF(neg, d, prec) case 'g', 'G': - // trailing zeros are removed. - if prec > d.nd { - prec = d.nd + // trailing fractional zeros in 'e' form will be trimmed. + eprec := prec + if eprec > d.nd && d.nd >= d.dp { + eprec = d.nd } // %e is used if the exponent from the conversion // is less than -4 or greater than or equal to the precision. // if precision was the shortest possible, use precision 6 for this decision. - eprec := prec if shortest { eprec = 6 } exp := d.dp - 1 if exp < -4 || exp >= eprec { + if prec > d.nd { + prec = d.nd + } return fmtE(neg, d, prec-1, fmt+'e'-'g') } + if prec > d.dp { + prec = d.nd + } return fmtF(neg, d, max(prec-d.dp, 0)) } diff --git a/src/pkg/strconv/ftoa_test.go b/src/pkg/strconv/ftoa_test.go index 85510b79c7..cc01ccd780 100644 --- a/src/pkg/strconv/ftoa_test.go +++ b/src/pkg/strconv/ftoa_test.go @@ -34,6 +34,17 @@ var ftoatests = []ftoaTest{ ftoaTest{200000, 'g', -1, "200000"}, ftoaTest{2000000, 'g', -1, "2e+06"}, + // g conversion and zero suppression + ftoaTest{400, 'g', 2, "4e+02"}, + ftoaTest{40, 'g', 2, "40"}, + ftoaTest{4, 'g', 2, "4"}, + ftoaTest{.4, 'g', 2, "0.4"}, + ftoaTest{.04, 'g', 2, "0.04"}, + ftoaTest{.004, 'g', 2, "0.004"}, + ftoaTest{.0004, 'g', 2, "0.0004"}, + ftoaTest{.00004, 'g', 2, "4e-05"}, + ftoaTest{.000004, 'g', 2, "4e-06"}, + ftoaTest{0, 'e', 5, "0.00000e+00"}, ftoaTest{0, 'f', 5, "0.00000"}, ftoaTest{0, 'g', 5, "0"},