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remove some magic numbers from float printing

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This commit is contained in:
MovingtoMars 2016-01-29 21:19:21 +13:00
parent 850f6d2d02
commit a6c2b013fd
1 changed files with 8 additions and 4 deletions
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12
std/std.zig
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@ -244,6 +244,10 @@ pub fn buf_print_u64(out_buf: []u8, x: u64) -> isize {
} }
pub fn buf_print_f64(out_buf: []u8, x: f64, decimals: isize) -> isize { pub fn buf_print_f64(out_buf: []u8, x: f64, decimals: isize) -> isize {
const numExpBits = 11;
const numRawSigBits = 52; // not including implicit 1 bit
const expBias = 1023;
var decs = decimals; var decs = decimals;
if (decs >= max_u64_base10_digits) { if (decs >= max_u64_base10_digits) {
decs = max_u64_base10_digits - 1; decs = max_u64_base10_digits - 1;
@ -277,8 +281,8 @@ pub fn buf_print_f64(out_buf: []u8, x: f64, decimals: isize) -> isize {
len += 1; len += 1;
} }
const rexponent: i64 = i64((bits >> 52) & ((1 << 11) - 1)); const rexponent: i64 = i64((bits >> numRawSigBits) & ((1 << numExpBits) - 1));
const exponent = rexponent - 1023 - 52; const exponent = rexponent - expBias - numRawSigBits;
if (rexponent == 0) { if (rexponent == 0) {
buf[len] = '0'; buf[len] = '0';
@ -287,12 +291,12 @@ pub fn buf_print_f64(out_buf: []u8, x: f64, decimals: isize) -> isize {
return len; return len;
} }
const sig = (bits & ((1 << 52) - 1)) | (1 << 52); const sig = (bits & ((1 << numRawSigBits) - 1)) | (1 << numRawSigBits);
if (exponent >= 0) { if (exponent >= 0) {
// number is an integer // number is an integer
if (exponent >= 11) { if (exponent >= 64 - 53) {
// use XeX form // use XeX form
// TODO support printing large floats // TODO support printing large floats