1 files changed, 14 insertions, 1 deletions
diff --git a/lib/std/fmt/parse_float.zig b/lib/std/fmt/parse_float.zig
index 3173d749b4..1f6d7222ac 100644
--- a/lib/std/fmt/parse_float.zig
+++ b/lib/std/fmt/parse_float.zig
@@ -34,7 +34,7 @@
 // - Only supports round-to-zero
 // - Does not handle denormals
 
-const std = @import("../std.zig");
+const std = @import("std");
 const ascii = std.ascii;
 
 // The mantissa field in FloatRepr is 64bit wide and holds only 19 digits
@@ -231,6 +231,8 @@ fn parseRepr(s: []const u8, n: *FloatRepr) !ParseResult {
                 } else if (c == '.') {
                     i += 1;
                     state = .LeadingFractionalZeros;
+                } else if (c == '_') {
+                    i += 1;
                 } else {
                     state = .MantissaIntegral;
                 }
@@ -259,6 +261,8 @@ fn parseRepr(s: []const u8, n: *FloatRepr) !ParseResult {
                 } else if (c == '.') {
                     i += 1;
                     state = .MantissaFractional;
+                } else if (c == '_') {
+                    i += 1;
                 } else {
                     state = .MantissaFractional;
                 }
@@ -276,6 +280,8 @@ fn parseRepr(s: []const u8, n: *FloatRepr) !ParseResult {
                 } else if (c == 'e' or c == 'E') {
                     i += 1;
                     state = .ExponentSign;
+                } else if (c == '_') {
+                    i += 1;
                 } else {
                     state = .ExponentSign;
                 }
@@ -283,6 +289,8 @@ fn parseRepr(s: []const u8, n: *FloatRepr) !ParseResult {
             .ExponentSign => {
                 if (c == '+') {
                     i += 1;
+                } else if (c == '_') {
+                    return error.InvalidCharacter;
                 } else if (c == '-') {
                     negative_exp = true;
                     i += 1;
@@ -293,6 +301,8 @@ fn parseRepr(s: []const u8, n: *FloatRepr) !ParseResult {
             .LeadingExponentZeros => {
                 if (c == '0') {
                     i += 1;
+                } else if (c == '_') {
+                    i += 1;
                 } else {
                     state = .Exponent;
                 }
@@ -305,6 +315,8 @@ fn parseRepr(s: []const u8, n: *FloatRepr) !ParseResult {
                     }
 
                     i += 1;
+                } else if (c == '_') {
+                    i += 1;
                 } else {
                     return error.InvalidCharacter;
                 }
@@ -405,6 +417,7 @@ test "fmt.parseFloat" {
         try expectEqual(try parseFloat(T, "-INF"), -std.math.inf(T));
 
         try expectEqual(try parseFloat(T, "0.4e0066999999999999999999999999999999999999999999999999999"), std.math.inf(T));
+        try expect(approxEqAbs(T, try parseFloat(T, "0_1_2_3_4_5_6.7_8_9_0_0_0e0_0_1_0"), @as(T, 123456.789000e10), epsilon));
 
         if (T != f16) {
             try expect(approxEqAbs(T, try parseFloat(T, "1e-2"), 0.01, epsilon));