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Date: Fri, 19 Jul 2019 14:57:46 +0300
From: Konstantin Osipov <kostja@tarantool.org>
Subject: Re: [tarantool-patches] [PATCH] decimal: add methods truncate and
 set_scale
Message-ID: <20190719115746.GA29078@atlas>
References: <20190719112136.23483-1-sergepetrenko@tarantool.org>
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In-Reply-To: <20190719112136.23483-1-sergepetrenko@tarantool.org>
To: tarantool-patches@freelists.org
Cc: vdavydov.dev@gmail.com, Serge Petrenko <sergepetrenko@tarantool.org>
List-ID: <tarantool-patches.dev.tarantool.org>

* Serge Petrenko <sergepetrenko@tarantool.org> [19/07/19 14:42]:
> This patch adds 2 methods to decimal library and lua module:
> truncate will remove all trailing fractional zeros and set_scale will
> either perform rounding or append excess fractional zeros.
> 

Please note that it is Trim in the ldec library.
truncate() has a slightly different meaning.

> +decimal_t *
> +decimal_truncate(decimal_t *dec)
> +{
> +	decimal_t *res = decNumberTrim(dec);
> +
> +	/* No errors are possible */
> +	assert(res == dec);
> +	return res;
> +}
> +
> +decimal_t *
> +decimal_set_scale(decimal_t *dec, int scale)
> +{
> +	if (scale < 0)
> +		return NULL;
> +	if (scale <= decimal_scale(dec))
> +		return decimal_round(dec, scale);
> +	/* how much zeros shoud we append. */
> +	int delta = scale + dec->exponent;
> +	if (scale > DECIMAL_MAX_DIGITS || dec->digits + delta > DECIMAL_MAX_DIGITS)
> +		return NULL;
> +	decimal_t new_scale;
> +	decimal_from_int64(&new_scale, -scale);
> +	decNumberRescale(dec, dec, &new_scale, &decimal_context);
> +	assert(decimal_check_status(dec, &decimal_context) != NULL);
> +	return dec;

Please also note here: the name is rescale(), not set_scale(). The
meaning of set_scale() is slightly different.

Please use less confusing names.

otherwise lgtm.

-- 
Konstantin Osipov, Moscow, Russia