[{"id":39206,"web_url":"https://patchwork.libcamera.org/comment/39206/","msgid":"<178204426117.1686300.2959076045881961108@ping.linuxembedded.co.uk>","date":"2026-06-21T12:17:41","subject":"Re: [PATCH 2/4] libcamera: vector: Swap order of arguments to\n\tapply()","submitter":{"id":4,"url":"https://patchwork.libcamera.org/api/people/4/","name":"Kieran Bingham","email":"kieran.bingham@ideasonboard.com"},"content":"Quoting Laurent Pinchart (2026-06-21 01:23:03)\n> The Vector class is lacking a clamp() function, which will take two\n> scalar parameters. To support that, the apply() function will need to be\n> converted to variable number of parameters. This will require passing\n> the scalar parameter last, to make automatic template arguments\n> deduction possible.\n> \n> In preparation for that change, swap the arguments to apply() to pass\n> the operation before the scalar parameter last. Only one variant of\n> apply() strictly requires this change, arguments to the three other\n> functions are also swapped for consistency. Also for consistency, swap\n> the template arguments as well.\n\nThis order actually feels more realistic to me.\n\n 'Add this-value' instead of 'this-value add'.\n\n\nReviewed-by: Kieran Bingham \n\n> \n> Signed-off-by: Laurent Pinchart \n> ---\n> include/libcamera/internal/vector.h | 56 ++++++++++++++---------------\n> 1 file changed, 28 insertions(+), 28 deletions(-)\n> \n> diff --git a/include/libcamera/internal/vector.h b/include/libcamera/internal/vector.h\n> index 04ba5d847b7d..256de1d1c53a 100644\n> --- a/include/libcamera/internal/vector.h\n> +++ b/include/libcamera/internal/vector.h\n> @@ -73,116 +73,116 @@ public:\n> \n> constexpr Vector operator+(const Vector &other) const\n> {\n> - return apply(*this, other, std::plus<>{});\n> + return apply(*this, std::plus<>{}, other);\n> }\n> \n> constexpr Vector operator+(T scalar) const\n> {\n> - return apply(*this, scalar, std::plus<>{});\n> + return apply(*this, std::plus<>{}, scalar);\n> }\n> \n> constexpr Vector operator-(const Vector &other) const\n> {\n> - return apply(*this, other, std::minus<>{});\n> + return apply(*this, std::minus<>{}, other);\n> }\n> \n> constexpr Vector operator-(T scalar) const\n> {\n> - return apply(*this, scalar, std::minus<>{});\n> + return apply(*this, std::minus<>{}, scalar);\n> }\n> \n> constexpr Vector operator*(const Vector &other) const\n> {\n> - return apply(*this, other, std::multiplies<>{});\n> + return apply(*this, std::multiplies<>{}, other);\n> }\n> \n> constexpr Vector operator*(T scalar) const\n> {\n> - return apply(*this, scalar, std::multiplies<>{});\n> + return apply(*this, std::multiplies<>{}, scalar);\n> }\n> \n> constexpr Vector operator/(const Vector &other) const\n> {\n> - return apply(*this, other, std::divides<>{});\n> + return apply(*this, std::divides<>{}, other);\n> }\n> \n> constexpr Vector operator/(T scalar) const\n> {\n> - return apply(*this, scalar, std::divides<>{});\n> + return apply(*this, std::divides<>{}, scalar);\n> }\n> \n> constexpr Vector operator>>(unsigned int shift) const\n> {\n> static_assert(std::is_integral_v,\n> \"Vector::operator>> requires an integer element type\");\n> - return apply(*this, shift, [](T a, unsigned int b) { return a >> b; });\n> + return apply(*this, [](T a, unsigned int b) { return a >> b; }, shift);\n> }\n> \n> Vector &operator+=(const Vector &other)\n> {\n> - return apply(other, [](T a, T b) { return a + b; });\n> + return apply([](T a, T b) { return a + b; }, other);\n> }\n> \n> Vector &operator+=(T scalar)\n> {\n> - return apply(scalar, [](T a, T b) { return a + b; });\n> + return apply([](T a, T b) { return a + b; }, scalar);\n> }\n> \n> Vector &operator-=(const Vector &other)\n> {\n> - return apply(other, [](T a, T b) { return a - b; });\n> + return apply([](T a, T b) { return a - b; }, other);\n> }\n> \n> Vector &operator-=(T scalar)\n> {\n> - return apply(scalar, [](T a, T b) { return a - b; });\n> + return apply([](T a, T b) { return a - b; }, scalar);\n> }\n> \n> Vector &operator*=(const Vector &other)\n> {\n> - return apply(other, [](T a, T b) { return a * b; });\n> + return apply([](T a, T b) { return a * b; }, other);\n> }\n> \n> Vector &operator*=(T scalar)\n> {\n> - return apply(scalar, [](T a, T b) { return a * b; });\n> + return apply([](T a, T b) { return a * b; }, scalar);\n> }\n> \n> Vector &operator/=(const Vector &other)\n> {\n> - return apply(other, [](T a, T b) { return a / b; });\n> + return apply([](T a, T b) { return a / b; }, other);\n> }\n> \n> Vector &operator/=(T scalar)\n> {\n> - return apply(scalar, [](T a, T b) { return a / b; });\n> + return apply([](T a, T b) { return a / b; }, scalar);\n> }\n> \n> Vector &operator>>=(unsigned int shift)\n> {\n> static_assert(std::is_integral_v,\n> \"Vector::operator>>= requires an integer element type\");\n> - return apply(shift, [](T a, unsigned int b) { return a >> b; });\n> + return apply([](T a, unsigned int b) { return a >> b; }, shift);\n> }\n> \n> constexpr Vector min(const Vector &other) const\n> {\n> - return apply(*this, other, [](T a, T b) { return std::min(a, b); });\n> + return apply(*this, [](T a, T b) { return std::min(a, b); }, other);\n> }\n> \n> constexpr Vector min(T scalar) const\n> {\n> - return apply(*this, scalar, [](T a, T b) { return std::min(a, b); });\n> + return apply(*this, [](T a, T b) { return std::min(a, b); }, scalar);\n> }\n> \n> constexpr Vector max(const Vector &other) const\n> {\n> - return apply(*this, other, [](T a, T b) { return std::max(a, b); });\n> + return apply(*this, [](T a, T b) { return std::max(a, b); }, other);\n> }\n> \n> constexpr Vector max(T scalar) const\n> {\n> - return apply(*this, scalar, [](T a, T b) -> T { return std::max(a, b); });\n> + return apply(*this, [](T a, T b) -> T { return std::max(a, b); }, scalar);\n> }\n> \n> constexpr T dot(const Vector &other) const\n> @@ -264,7 +264,7 @@ public:\n> \n> private:\n> template\n> - static constexpr Vector apply(const Vector &lhs, const Vector &rhs, BinaryOp op)\n> + static constexpr Vector apply(const Vector &lhs, BinaryOp op, const Vector &rhs)\n> {\n> Vector result;\n> std::transform(lhs.data_.begin(), lhs.data_.end(),\n> @@ -274,8 +274,8 @@ private:\n> return result;\n> }\n> \n> - template\n> - static constexpr Vector apply(const Vector &lhs, U rhs, BinaryOp op)\n> + template\n> + static constexpr Vector apply(const Vector &lhs, BinaryOp op, U rhs)\n> {\n> Vector result;\n> std::transform(lhs.data_.begin(), lhs.data_.end(),\n> @@ -286,7 +286,7 @@ private:\n> }\n> \n> template\n> - Vector &apply(const Vector &other, BinaryOp op)\n> + Vector &apply(BinaryOp op, const Vector &other)\n> {\n> auto itOther = other.data_.begin();\n> std::for_each(data_.begin(), data_.end(),\n> @@ -295,8 +295,8 @@ private:\n> return *this;\n> }\n> \n> - template\n> - Vector &apply(U scalar, BinaryOp op)\n> + template\n> + Vector &apply(BinaryOp op, U scalar)\n> {\n> std::for_each(data_.begin(), data_.end(),\n> [&op, scalar](T &v) { v = op(v, scalar); });\n> -- \n> Regards,\n> \n> Laurent Pinchart\n>","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 88C06C3261\n\tfor ;\n\tSun, 21 Jun 2026 12:17:46 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id A308D656EF;\n\tSun, 21 Jun 2026 14:17:45 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 6C88B61F3F\n\tfor ;\n\tSun, 21 Jun 2026 14:17:44 +0200 (CEST)","from monstersaurus.ideasonboard.com\n\t(cpc89244-aztw30-2-0-cust6594.18-1.cable.virginm.net [86.31.185.195])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 22BDE236;\n\tSun, 21 Jun 2026 14:17:07 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; 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To support that, the apply() function will need to be\n> converted to variable number of parameters. This will require passing\n> the scalar parameter last, to make automatic template arguments\n> deduction possible.\n> \n> In preparation for that change, swap the arguments to apply() to pass\n> the operation before the scalar parameter last. Only one variant of\n> apply() strictly requires this change, arguments to the three other\n> functions are also swapped for consistency. Also for consistency, swap\n> the template arguments as well.\n> \n> Signed-off-by: Laurent Pinchart \n> ---\n\nReviewed-by: Barnabás Pőcze \n\n\n> include/libcamera/internal/vector.h | 56 ++++++++++++++---------------\n> 1 file changed, 28 insertions(+), 28 deletions(-)\n> \n> diff --git a/include/libcamera/internal/vector.h b/include/libcamera/internal/vector.h\n> index 04ba5d847b7d..256de1d1c53a 100644\n> --- a/include/libcamera/internal/vector.h\n> +++ b/include/libcamera/internal/vector.h\n> @@ -73,116 +73,116 @@ public:\n> \n> \tconstexpr Vector operator+(const Vector &other) const\n> \t{\n> -\t\treturn apply(*this, other, std::plus<>{});\n> +\t\treturn apply(*this, std::plus<>{}, other);\n> \t}\n> \n> \tconstexpr Vector operator+(T scalar) const\n> \t{\n> -\t\treturn apply(*this, scalar, std::plus<>{});\n> +\t\treturn apply(*this, std::plus<>{}, scalar);\n> \t}\n> \n> \tconstexpr Vector operator-(const Vector &other) const\n> \t{\n> -\t\treturn apply(*this, other, std::minus<>{});\n> +\t\treturn apply(*this, std::minus<>{}, other);\n> \t}\n> \n> \tconstexpr Vector operator-(T scalar) const\n> \t{\n> -\t\treturn apply(*this, scalar, std::minus<>{});\n> +\t\treturn apply(*this, std::minus<>{}, scalar);\n> \t}\n> \n> \tconstexpr Vector operator*(const Vector &other) const\n> \t{\n> -\t\treturn apply(*this, other, std::multiplies<>{});\n> +\t\treturn apply(*this, std::multiplies<>{}, other);\n> \t}\n> \n> \tconstexpr Vector operator*(T scalar) const\n> \t{\n> -\t\treturn apply(*this, scalar, std::multiplies<>{});\n> +\t\treturn apply(*this, std::multiplies<>{}, scalar);\n> \t}\n> \n> \tconstexpr Vector operator/(const Vector &other) const\n> \t{\n> -\t\treturn apply(*this, other, std::divides<>{});\n> +\t\treturn apply(*this, std::divides<>{}, other);\n> \t}\n> \n> \tconstexpr Vector operator/(T scalar) const\n> \t{\n> -\t\treturn apply(*this, scalar, std::divides<>{});\n> +\t\treturn apply(*this, std::divides<>{}, scalar);\n> \t}\n> \n> \tconstexpr Vector operator>>(unsigned int shift) const\n> \t{\n> \t\tstatic_assert(std::is_integral_v,\n> \t\t\t \"Vector::operator>> requires an integer element type\");\n> -\t\treturn apply(*this, shift, [](T a, unsigned int b) { return a >> b; });\n> +\t\treturn apply(*this, [](T a, unsigned int b) { return a >> b; }, shift);\n> \t}\n> \n> \tVector &operator+=(const Vector &other)\n> \t{\n> -\t\treturn apply(other, [](T a, T b) { return a + b; });\n> +\t\treturn apply([](T a, T b) { return a + b; }, other);\n> \t}\n> \n> \tVector &operator+=(T scalar)\n> \t{\n> -\t\treturn apply(scalar, [](T a, T b) { return a + b; });\n> +\t\treturn apply([](T a, T b) { return a + b; }, scalar);\n> \t}\n> \n> \tVector &operator-=(const Vector &other)\n> \t{\n> -\t\treturn apply(other, [](T a, T b) { return a - b; });\n> +\t\treturn apply([](T a, T b) { return a - b; }, other);\n> \t}\n> \n> \tVector &operator-=(T scalar)\n> \t{\n> -\t\treturn apply(scalar, [](T a, T b) { return a - b; });\n> +\t\treturn apply([](T a, T b) { return a - b; }, scalar);\n> \t}\n> \n> \tVector &operator*=(const Vector &other)\n> \t{\n> -\t\treturn apply(other, [](T a, T b) { return a * b; });\n> +\t\treturn apply([](T a, T b) { return a * b; }, other);\n> \t}\n> \n> \tVector &operator*=(T scalar)\n> \t{\n> -\t\treturn apply(scalar, [](T a, T b) { return a * b; });\n> +\t\treturn apply([](T a, T b) { return a * b; }, scalar);\n> \t}\n> \n> \tVector &operator/=(const Vector &other)\n> \t{\n> -\t\treturn apply(other, [](T a, T b) { return a / b; });\n> +\t\treturn apply([](T a, T b) { return a / b; }, other);\n> \t}\n> \n> \tVector &operator/=(T scalar)\n> \t{\n> -\t\treturn apply(scalar, [](T a, T b) { return a / b; });\n> +\t\treturn apply([](T a, T b) { return a / b; }, scalar);\n> \t}\n> \n> \tVector &operator>>=(unsigned int shift)\n> \t{\n> \t\tstatic_assert(std::is_integral_v,\n> \t\t\t \"Vector::operator>>= requires an integer element type\");\n> -\t\treturn apply(shift, [](T a, unsigned int b) { return a >> b; });\n> +\t\treturn apply([](T a, unsigned int b) { return a >> b; }, shift);\n> \t}\n> \n> \tconstexpr Vector min(const Vector &other) const\n> \t{\n> -\t\treturn apply(*this, other, [](T a, T b) { return std::min(a, b); });\n> +\t\treturn apply(*this, [](T a, T b) { return std::min(a, b); }, other);\n> \t}\n> \n> \tconstexpr Vector min(T scalar) const\n> \t{\n> -\t\treturn apply(*this, scalar, [](T a, T b) { return std::min(a, b); });\n> +\t\treturn apply(*this, [](T a, T b) { return std::min(a, b); }, scalar);\n> \t}\n> \n> \tconstexpr Vector max(const Vector &other) const\n> \t{\n> -\t\treturn apply(*this, other, [](T a, T b) { return std::max(a, b); });\n> +\t\treturn apply(*this, [](T a, T b) { return std::max(a, b); }, other);\n> \t}\n> \n> \tconstexpr Vector max(T scalar) const\n> \t{\n> -\t\treturn apply(*this, scalar, [](T a, T b) -> T { return std::max(a, b); });\n> +\t\treturn apply(*this, [](T a, T b) -> T { return std::max(a, b); }, scalar);\n> \t}\n> \n> \tconstexpr T dot(const Vector &other) const\n> @@ -264,7 +264,7 @@ public:\n> \n> private:\n> \ttemplate\n> -\tstatic constexpr Vector apply(const Vector &lhs, const Vector &rhs, BinaryOp op)\n> +\tstatic constexpr Vector apply(const Vector &lhs, BinaryOp op, const Vector &rhs)\n> \t{\n> \t\tVector result;\n> \t\tstd::transform(lhs.data_.begin(), lhs.data_.end(),\n> @@ -274,8 +274,8 @@ private:\n> \t\treturn result;\n> \t}\n> \n> -\ttemplate\n> -\tstatic constexpr Vector apply(const Vector &lhs, U rhs, BinaryOp op)\n> +\ttemplate\n> +\tstatic constexpr Vector apply(const Vector &lhs, BinaryOp op, U rhs)\n> \t{\n> \t\tVector result;\n> \t\tstd::transform(lhs.data_.begin(), lhs.data_.end(),\n> @@ -286,7 +286,7 @@ private:\n> \t}\n> \n> \ttemplate\n> -\tVector &apply(const Vector &other, BinaryOp op)\n> +\tVector &apply(BinaryOp op, const Vector &other)\n> \t{\n> \t\tauto itOther = other.data_.begin();\n> \t\tstd::for_each(data_.begin(), data_.end(),\n> @@ -295,8 +295,8 @@ private:\n> \t\treturn *this;\n> \t}\n> \n> -\ttemplate\n> -\tVector &apply(U scalar, BinaryOp op)\n> +\ttemplate\n> +\tVector &apply(BinaryOp op, U scalar)\n> \t{\n> \t\tstd::for_each(data_.begin(), data_.end(),\n> \t\t\t [&op, scalar](T &v) { v = op(v, scalar); });","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 8EE5BC3303\n\tfor ;\n\tMon, 22 Jun 2026 07:54:05 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 41A5465711;\n\tMon, 22 Jun 2026 09:54:05 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 954A0623CC\n\tfor ;\n\tMon, 22 Jun 2026 09:54:02 +0200 (CEST)","from [192.168.33.39] (185.221.141.133.nat.pool.zt.hu\n\t[185.221.141.133])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 6B38C1E6;\n\tMon, 22 Jun 2026 09:53:24 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"DYwGkdvQ\"; 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