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fix: remove trailing zeros and handle zero and zero precision for %g in string/base/format-interpolate #16538

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fix: remove trailing zeros and handle zero and zero precision for %g in string/base/format-interpolate #16538

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30 changes: 18 additions & 12 deletions lib/node_modules/@stdlib/string/base/format-interpolate/lib/format_double.js
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,6 @@
// MODULES //

// NOTE: for the following, we explicitly avoid using stdlib packages in this particular package in order to avoid circular dependencies.
var abs = Math.abs; // eslint-disable-line stdlib/no-builtin-math
var lowercase = String.prototype.toLowerCase;
var uppercase = String.prototype.toUpperCase;
var replace = String.prototype.replace;
Expand All @@ -31,9 +30,11 @@ var replace = String.prototype.replace;

var RE_EXP_POS_DIGITS = /e\+(\d)$/;
var RE_EXP_NEG_DIGITS = /e-(\d)$/;
var RE_ONLY_DIGITS = /^(\d+)$/;
var RE_DIGITS_BEFORE_EXP = /^(\d+)e/;
var RE_TRAILING_PERIOD_ZERO = /\.0$/;
var RE_ONLY_DIGITS = /^(-?\d+)$/;
var RE_DIGITS_BEFORE_EXP = /^(-?\d+)e/;
var RE_EXP = /e([+-]\d+)$/;
var RE_TRAILING_ZEROS = /(\.\d*?)0+$/;
var RE_TRAILING_PERIOD = /\.$/;
var RE_PERIOD_ZERO_EXP = /\.0*e/;
var RE_ZERO_BEFORE_EXP = /(\..*[^0])0*e/;

Expand All @@ -51,6 +52,7 @@ var RE_ZERO_BEFORE_EXP = /(\..*[^0])0*e/;
*/
function formatDouble( f, token ) {
var digits;
var exp;
var out;

switch ( token.specifier ) {
Expand All @@ -64,19 +66,23 @@ function formatDouble( f, token ) {
break;
case 'g':
case 'G':
if ( abs( f ) < 0.0001 ) {
digits = token.precision;
if ( digits > 0 ) {
digits -= 1;
// A precision of zero is treated as one significant digit:
digits = ( token.precision > 0 ) ? token.precision : 1;

// Use the exponent of the value rounded to `digits` significant digits to choose between exponential and fixed-point notation, as in C's `printf`:
out = f.toExponential( digits - 1 );
exp = RE_EXP.exec( out );
if ( exp ) {
exp = parseInt( exp[ 1 ], 10 );
if ( exp >= -4 && exp < digits ) {
out = f.toFixed( digits - 1 - exp );
}
out = f.toExponential( digits );
} else {
out = f.toPrecision( token.precision );
}
if ( !token.alternate ) {
out = replace.call( out, RE_ZERO_BEFORE_EXP, '$1e' );
out = replace.call( out, RE_PERIOD_ZERO_EXP, 'e' );
out = replace.call( out, RE_TRAILING_PERIOD_ZERO, '' );
out = replace.call( out, RE_TRAILING_ZEROS, '$1' );
out = replace.call( out, RE_TRAILING_PERIOD, '' );
}
break;
default:
Expand Down
117 changes: 117 additions & 0 deletions lib/node_modules/@stdlib/string/base/format-interpolate/test/test.js
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Expand Up @@ -796,6 +796,123 @@ tape( 'the function returns a formatted string (`G` specifier, alternate form)',
t.end();
});

tape( 'the function returns a formatted string (`g` specifier, trailing zeros)', function test( t ) {
var expected;
var values;
var actual;
var tokens;
var i;

tokens = formatTokenize( '%g' );
values = [ 1.5, -2.5, 100, 0.5, 0.0001, 123.0, 1.0e-5 ];
expected = [ '1.5', '-2.5', '100', '0.5', '0.0001', '123', '1e-05' ];
for ( i = 0; i < values.length; i++ ) {
actual = formatInterpolate( tokens, values[ i ] );
t.strictEqual( actual, expected[ i ], 'returns expected output' );
}

tokens = formatTokenize( '%.3g' );
actual = formatInterpolate( tokens, 0.1 );
expected = '0.1';
t.strictEqual( actual, expected, 'returns expected output' );

tokens = formatTokenize( '%10g|' );
actual = formatInterpolate( tokens, 1.5 );
expected = ' 1.5|';
t.strictEqual( actual, expected, 'returns expected output' );

tokens = formatTokenize( '%G' );
actual = formatInterpolate( tokens, 0.5 );
expected = '0.5';
t.strictEqual( actual, expected, 'returns expected output' );

t.end();
});

tape( 'the function returns a formatted string (`g` specifier, zero)', function test( t ) {
var expected;
var tokens;
var actual;

tokens = formatTokenize( '%g' );
actual = formatInterpolate( tokens, 0 );
expected = '0';
t.strictEqual( actual, expected, 'returns expected output' );

tokens = formatTokenize( '%#g' );
actual = formatInterpolate( tokens, 0 );
expected = '0.00000';
t.strictEqual( actual, expected, 'returns expected output' );

t.end();
});

tape( 'the function returns a formatted string (`g` specifier, zero precision)', function test( t ) {
var expected;
var tokens;
var actual;

tokens = formatTokenize( '%.0g' );
actual = formatInterpolate( tokens, 1.5 );
expected = '2';
t.strictEqual( actual, expected, 'returns expected output' );

tokens = formatTokenize( '%.0g' );
actual = formatInterpolate( tokens, 15 );
expected = '2e+01';
t.strictEqual( actual, expected, 'returns expected output' );

t.end();
});

tape( 'the function returns a formatted string (`g` specifier, switching between fixed-point and exponential notation)', function test( t ) {
var expected;
var tokens;
var actual;

tokens = formatTokenize( '%g' );
actual = formatInterpolate( tokens, 123456 );
expected = '123456';
t.strictEqual( actual, expected, 'returns expected output' );

actual = formatInterpolate( tokens, 1234567 );
expected = '1.23457e+06';
t.strictEqual( actual, expected, 'returns expected output' );

actual = formatInterpolate( tokens, 999999.5 );
expected = '1e+06';
t.strictEqual( actual, expected, 'returns expected output' );

actual = formatInterpolate( tokens, 0.00009999995 );
expected = '0.0001';
t.strictEqual( actual, expected, 'returns expected output' );

t.end();
});

tape( 'the function returns a formatted string (`g` specifier, alternate form, negative values)', function test( t ) {
var expected;
var tokens;
var actual;

tokens = formatTokenize( '%#.3g' );
actual = formatInterpolate( tokens, -340.12 );
expected = '-340.';
t.strictEqual( actual, expected, 'returns expected output' );

tokens = formatTokenize( '%#g' );
actual = formatInterpolate( tokens, -1.5 );
expected = '-1.50000';
t.strictEqual( actual, expected, 'returns expected output' );

tokens = formatTokenize( '%#.0f' );
actual = formatInterpolate( tokens, -3 );
expected = '-3.';
t.strictEqual( actual, expected, 'returns expected output' );

t.end();
});

tape( 'the function returns a formatted string (`f` specifier, minimum width)', function test( t ) {
var expected;
var tokens;
Expand Down
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