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make JS trunc polyfill opt-in, closes nim-lang#16144 (nim-lang#19183)
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metagn authored and Jaremy Creechley committed Dec 1, 2021
1 parent 8c287f0 commit 30286fb
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8 changes: 7 additions & 1 deletion changelog.md
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## Changes affecting backward compatibility


- The `Math.trunc` polyfill for targeting Internet Explorer was
previously emitted for every JavaScript output file except if
the symbol `nodejs` was defined via `-d:nodejs`. Now, it is only
emitted if the symbol `nimJsMathTruncPolyfill` is defined. If you are
targeting Internet Explorer, you may choose to enable this option
or define your own `Math.trunc` polyfill using the [`emit` pragma](https://nim-lang.org/docs/manual.html#implementation-specific-pragmas-emit-pragma). Nim uses
`Math.trunc` for the division and modulo operators for integers.

## Standard library additions and changes

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6 changes: 3 additions & 3 deletions lib/system/jssys.nim
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Expand Up @@ -763,13 +763,13 @@ proc nimParseBiggestFloat(s: string, number: var BiggestFloat, start: int): int

# Workaround for IE, IE up to version 11 lacks 'Math.trunc'. We produce
# 'Math.trunc' for Nim's ``div`` and ``mod`` operators:
const jsMathTrunc = """
when defined(nimJsMathTruncPolyfill):
{.emit: """
if (!Math.trunc) {
Math.trunc = function(v) {
v = +v;
if (!isFinite(v)) return v;
return (v - v % 1) || (v < 0 ? -0 : v === 0 ? v : 0);
};
}
"""
when not defined(nodejs): {.emit: jsMathTrunc .}
""".}

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