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Unless explicitly stated, specifications that override the semantics of HTML elements do not override the requirements on DOM objects representing those elements. User agents that process HTML and XML documents purely to render non-interactive versions of them must comply to the same conformance criteria as Web browsers, except that they are exempt from requirements regarding user interaction. Typical examples of non-interactive presentation user agents are printers static UAs and overhead displays dynamic UAs.
It is expected that most static non-interactive presentation user agents will also opt to lack scripting support. A non-interactive but dynamic presentation UA would still execute scripts, allowing forms to be dynamically submitted, and so forth. However, since the concept of "focus" is irrelevant when the user cannot interact with the document, the UA would not need to support any of the focus-related DOM APIs.
User agents, whether interactive or not, may be designated possibly as a user option as supporting the suggested default rendering defined by this specification. This is not required. In particular, even user agents that do implement the suggested default rendering are encouraged to offer settings that override this default to improve the experience for the user, e. User agents that are designated as supporting the suggested default rendering must, while so designated, implement the rules the rendering section defines as the behavior that user agents are expected to implement.
Implementations that do not support scripting or which have their scripting features disabled entirely are exempt from supporting the events and DOM interfaces mentioned in this specification. For the parts of this specification that are defined in terms of an events model or in terms of the DOM, such user agents must still act as if events and the DOM were supported. Scripting can form an integral part of an application. Web browsers that do not support scripting, or that have scripting disabled, might be unable to fully convey the author's intent.
Conformance checkers must verify that a document conforms to the applicable conformance criteria described in this specification. Automated conformance checkers are exempt from detecting errors that require interpretation of the author's intent for example, while a document is non-conforming if the content of a blockquote element is not a quote, conformance checkers running without the input of human judgement do not have to check that blockquote elements only contain quoted material. Conformance checkers must check that the input document conforms when parsed without a browsing context meaning that no scripts are run, and that the parser's scripting flag is disabled , and should also check that the input document conforms when parsed with a browsing context in which scripts execute, and that the scripts never cause non-conforming states to occur other than transiently during script execution itself.
The term "HTML validator" can be used to refer to a conformance checker that itself conforms to the applicable requirements of this specification. Also, since neither of the two authoring formats defined in this specification are applications of SGML, a validating SGML system cannot constitute a conformance checker either. A conformance checker must check for the first two. A simple DTD-based validator only checks for the first class of errors and is therefore not a conforming conformance checker according to this specification.
Applications and tools that process HTML and XML documents for reasons other than to either render the documents or check them for conformance should act in accordance with the semantics of the documents that they process. A tool that generates document outlines but increases the nesting level for each paragraph and does not increase the nesting level for each section would not be conforming.
Authoring tools and markup generators must generate conforming documents. Conformance criteria that apply to authors also apply to authoring tools, where appropriate. Authoring tools are exempt from the strict requirements of using elements only for their specified purpose, but only to the extent that authoring tools are not yet able to determine author intent.
However, authoring tools must not automatically misuse elements or encourage their users to do so. For example, it is not conforming to use an address element for arbitrary contact information; that element can only be used for marking up contact information for its nearest article or body element ancestor. However, since an authoring tool is likely unable to determine the difference, an authoring tool is exempt from that requirement. This does not mean, though, that authoring tools can use address elements for any block of italics text for instance ; it just means that the authoring tool doesn't have to verify that when the user uses a tool for inserting contact information for an article element, that the user really is doing that and not inserting something else instead.
In terms of conformance checking, an editor has to output documents that conform to the same extent that a conformance checker will verify. When an authoring tool is used to edit a non-conforming document, it may preserve the conformance errors in sections of the document that were not edited during the editing session i. However, an authoring tool must not claim that the output is conformant if errors have been so preserved. The former is the preferred mechanism for tools that author HTML, since the structure in the source information can be used to make informed choices regarding which HTML elements and attributes are most appropriate.
WYSIWYG tools should use elements they know are appropriate, and should not use elements that they do not know to be appropriate. This might in certain extreme cases mean limiting the use of flow elements to just a few elements, like div , b , i , and span and making liberal use of the style attribute. All authoring tools, whether WYSIWYG or not, should make a best effort attempt at enabling users to create well-structured, semantically rich, media-independent content. User agents may impose implementation-specific limits on otherwise unconstrained inputs, e.
For compatibility with existing content and prior specifications, this specification describes two authoring formats: one based on XML , and one using a custom format inspired by SGML referred to as the HTML syntax. Implementations must support at least one of these two formats, although supporting both is encouraged. Some conformance requirements are phrased as requirements on elements, attributes, methods or objects. Such requirements fall into two categories: those describing content model restrictions, and those describing implementation behavior.
Those in the former category are requirements on documents and authoring tools. Those in the second category are requirements on user agents. Similarly, some conformance requirements are phrased as requirements on authors; such requirements are to be interpreted as conformance requirements on the documents that authors produce.
In other words, this specification does not distinguish between conformance criteria on authors and conformance criteria on documents. The Unicode character set is used to represent textual data, and Encoding defines requirements around character encodings. This specification introduces terminology based on the terms defined in those specifications, as described earlier. Data mining tools and other user agents that perform operations on content without running scripts, evaluating CSS or XPath expressions, or otherwise exposing the resulting DOM to arbitrary content, may "support namespaces" by just asserting that their DOM node analogues are in certain namespaces, without actually exposing the namespace strings.
For instance, the colon has no special meaning in HTML element names. The Name production is defined in XML. The term throw in this specification is used as defined in Web IDL. When this specification requires a user agent to create a Date object representing a particular time which could be the special value Not-a-Number , the milliseconds component of that time, if any, must be truncated to an integer, and the time value of the newly created Date object must represent the resulting truncated time.
Implementations must support Media Queries. While support for CSS as a whole is not required of implementations of this specification though it is encouraged, at least for Web browsers , some features are defined in terms of specific CSS requirements. When this specification requires that something be parsed according to a particular CSS grammar , the relevant algorithm in CSS Syntax must be followed, including error handling rules. For example, user agents are required to close all open constructs upon finding the end of a style sheet unexpectedly.
Thus, when parsing the string " rgb 0,0,0 " with a missing close-parenthesis for a color value, the close parenthesis is implied by this error handling rule, and a value is obtained the color 'black'. However, the similar construct " rgb 0,0, " with both a missing parenthesis and a missing "blue" value cannot be parsed, as closing the open construct does not result in a viable value.
If color is 'currentcolor' , then:. If element is not given, then set color to opaque black.
Goose Pimple Junction Mysteries by Amy Metz
Otherwise, set color to the computed value of the 'color' property of element. Return color. The terms intrinsic width and intrinsic height refer to the width dimension and the height dimension, respectively, of intrinsic dimensions. The following features are defined in CSS Overflow. The algorithm to update animations and send events is defined in Web Animations. Implementations may support WebVTT as a text track format for subtitles, captions, metadata, etc.
While support for MathML as a whole is not required by this specification though it is encouraged, at least for Web browsers , certain features depend upon small parts of MathML being implemented. While support for SVG as a whole is not required by this specification though it is encouraged, at least for Web browsers , certain features depend upon parts of SVG being implemented. This specification does not require support of any particular network protocol, style sheet language, scripting language, or any of the DOM specifications beyond those required in the list above.
Ex 3.3,1 - Chapter 3 Class 9 Coordinate Geometry
This specification might have certain additional requirements on character encodings, image formats, audio formats, and video formats in the respective sections. Vendor-specific proprietary user agent extensions to this specification are strongly discouraged. Documents must not use such extensions, as doing so reduces interoperability and fragments the user base, allowing only users of specific user agents to access the content in question. All extensions must be defined so that the use of extensions neither contradicts nor causes the non-conformance of functionality defined in the specification.
For example, while strongly discouraged from doing so, an implementation could add a new IDL attribute " typeTime " to a control that returned the time it took the user to select the current value of a control say.
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On the other hand, defining a new control that appears in a form's elements array would be in violation of the above requirement, as it would violate the definition of elements given in this specification. When vendor-neutral extensions to this specification are needed, either this specification can be updated accordingly, or an extension specification can be written that overrides the requirements in this specification.
When someone applying this specification to their activities decides that they will recognize the requirements of such an extension specification, it becomes an applicable specification for the purposes of conformance requirements in this specification. Someone could write a specification that defines any arbitrary byte stream as conforming, and then claim that their random junk is conforming. However, that does not mean that their random junk actually is conforming for everyone's purposes: if someone else decides that that specification does not apply to their work, then they can quite legitimately say that the aforementioned random junk is just that, junk, and not conforming at all.
As far as conformance goes, what matters in a particular community is what that community agrees is applicable. User agents must treat elements and attributes that they do not understand as semantically neutral; leaving them in the DOM for DOM processors , and styling them according to CSS for CSS processors , but not inferring any meaning from them. When support for a feature is disabled e.
For example, if a particular feature is accessed via an attribute in a Web IDL interface, the attribute itself would be omitted from the objects that implement that interface — leaving the attribute on the object but making it return null or throw an exception is insufficient. Implementations of XPath 1. A QName in the node test is expanded into an expanded-name using the namespace declarations from the expression context.
This is the same way expansion is done for element type names in start and end-tags except that the default namespace declared with xmlns is not used: if the QName does not have a prefix, then the namespace URI is null this is the same way attribute names are expanded. It is an error if the QName has a prefix for which there is no namespace declaration in the expression context. If the QName has a prefix, then there must be a namespace declaration for this prefix in the expression context, and the corresponding namespace URI is the one that is associated with this prefix.
If the QName has no prefix and the principal node type of the axis is element, then the default element namespace is used. The default element namespace is a member of the context for the XPath expression. This is equivalent to adding the default element namespace feature of XPath 2. It is motivated by the desire to have implementations be compatible with legacy HTML content while still supporting the changes that this specification introduces to HTML regarding the namespace used for HTML elements, and by the desire to use XPath 1. This change is a willful violation of the XPath 1.
XSLT 1. If the transformation program outputs an element in no namespace, the processor must, prior to constructing the corresponding DOM element node, change the namespace of the element to the HTML namespace , ASCII-lowercase the element's local name, and ASCII-lowercase the names of any non-namespaced attributes on the element.
This requirement is a willful violation of the XSLT 1. Processors that serialize the output are unaffected. However, XSLT processors must stop parsing if they successfully complete, and must set the current document readiness first to " interactive " and then to " complete " if they are aborted. This specification does not specify how XSLT interacts with the navigation algorithm, how it fits in with the event loop , nor how error pages are to be handled e. Comparing two strings in a case-sensitive manner means comparing them exactly, code point for code point.
Except where otherwise stated, string comparisons must be performed in a case-sensitive manner.
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A string pattern is a prefix match for a string s when pattern is not longer than s and truncating s to pattern 's length leaves the two strings as matches of each other. This document defines the following policy-controlled features :. There are various places in HTML that accept particular data types, such as dates or numbers. This section describes what the conformance criteria for content in those formats is, and how to parse them. Implementors are strongly urged to carefully examine any third-party libraries they might consider using to implement the parsing of syntaxes described below.
For example, date libraries are likely to implement error handling behavior that differs from what is required in this specification, since error-handling behavior is often not defined in specifications that describe date syntaxes similar to those used in this specification, and thus implementations tend to vary greatly in how they handle errors.
Some of the micro-parsers described below follow the pattern of having an input variable that holds the string being parsed, and having a position variable pointing at the next character to parse in input. A number of attributes are boolean attributes. The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value. If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace.
The values "true" and "false" are not allowed on boolean attributes. To represent a false value, the attribute has to be omitted altogether. Here is an example of a checkbox that is checked and disabled. The checked and disabled attributes are the boolean attributes. Some attributes are defined as taking one of a finite set of keywords. Such attributes are called enumerated attributes.
The keywords are each defined to map to a particular state several keywords might map to the same state, in which case some of the keywords are synonyms of each other; additionally, some of the keywords can be said to be non-conforming, and are only in the specification for historical reasons. In addition, two default states can be given.
The first is the invalid value default , the second is the missing value default. If an enumerated attribute is specified, the attribute's value must be an ASCII case-insensitive match for one of the given keywords that are not said to be non-conforming, with no leading or trailing whitespace. When the attribute is specified, if its value is an ASCII case-insensitive match for one of the given keywords then that keyword's state is the state that the attribute represents.
If the attribute value matches none of the given keywords, but the attribute has an invalid value default , then the attribute represents that state. Otherwise, there is no default, and invalid values mean that there is no state represented. When the attribute is not specified, if there is a missing value default state defined, then that is the state represented by the missing attribute. Otherwise, the absence of the attribute means that there is no state represented. The rules for parsing integers are as given in the following algorithm.
When invoked, the steps must be followed in the order given, aborting at the first step that returns a value. This algorithm will return either an integer or an error. Let input be the string being parsed. Let position be a pointer into input , initially pointing at the start of the string. Let sign have the value "positive". If position is past the end of input , return an error. Collect a sequence of code points that are ASCII digits from input given position , and interpret the resulting sequence as a base-ten integer.
Let value be that integer. If sign is "positive", return value , otherwise return the result of subtracting value from zero. A valid non-negative integer represents the number that is represented in base ten by that string of digits. The rules for parsing non-negative integers are as given in the following algorithm. This algorithm will return either zero, a positive integer, or an error. Let value be the result of parsing input using the rules for parsing integers.
If value is an error, return an error. If value is less than zero, return an error. Return value. If there is no E, then the exponent is treated as zero. The valid floating-point number concept is typically only used to restrict what is allowed for authors, while the user agent requirements use the rules for parsing floating-point number values below e.
However, in some cases the user agent requirements include checking if a string is a valid floating-point number e. The best representation of the number n as a floating-point number is the string obtained from running ToString n. The abstract operation ToString is not uniquely determined. When there are multiple possible strings that could be obtained from ToString for a particular value, the user agent must always return the same string for that value though it may differ from the value used by other user agents. The rules for parsing floating-point number values are as given in the following algorithm.
This algorithm must be aborted at the first step that returns something. This algorithm will return either a number or an error. Let value have the value 1. Let divisor have the value 1. Let exponent have the value 1. Multiply value by that integer. If position is past the end of input , jump to the step labeled conversion. Advance position to the next character. Fraction loop : Multiply divisor by ten.
Add the value of the character indicated by position , interpreted as a base-ten digit If position is past the end of input , then jump to the step labeled conversion. If the character indicated by position is an ASCII digit , jump back to the step labeled fraction loop in these substeps. If the character indicated by position is not an ASCII digit , then jump to the step labeled conversion. Multiply exponent by that integer. Multiply value by ten raised to the exponent th power. Let rounded-value be the number in S that is closest to value , selecting the number with an even significand if there are two equally close values.
Return rounded-value. This algorithm will return either a number greater than or equal to 0. Let position be a position variable for input , initially pointing at the start of input. If position is past the end of input or the code point at position within input is not an ASCII digit , then return failure. Let value be that number. If position is past the end of input , then return value as a length. Advance position by 1. If position is past the end of input or the code point at position within input is not an ASCII digit , then return the current dimension value with value , input , and position.
While true:. Multiply divisor by ten. Add the value of the code point at position within input , interpreted as a base-ten digit Return the current dimension value with value , input , and position. The current dimension value , given value , input , and position , is determined as follows:. Return value as a length. This algorithm will return either a number greater than 0.
Let value be the result of parsing input using the rules for parsing dimension values. If value is zero, return an error. If value is a percentage, return value as a percentage. In addition, there might be restrictions on the number of floating-point numbers that can be given, or on the range of values allowed. The rules for parsing a list of floating-point numbers are as follows:. Let numbers be an initially empty list of floating-point numbers. This list will be the result of this algorithm.
This skips past any leading delimiters. While position is not past the end of input :. This skips past leading garbage. Let number be the result of parsing unparsed number using the rules for parsing floating-point number values. If number is an error, set number to zero. Append number to numbers. This skips past the delimiter. Return numbers. These rules return a list of zero or more pairs consisting of a number and a unit, the unit being one of percentage , relative , and absolute.
Let raw input be the string being parsed. Split the string raw input on commas. Let raw tokens be the resulting list of tokens. For each token in raw tokens , run the following substeps:. Let input be the token. Let value be the number 0. Let unit be absolute. If position is past the end of input , set unit to relative and jump to the last substep.
If the character at position is an ASCII digit , collect a sequence of code points that are ASCII digits from input given position , interpret the resulting sequence as an integer in base ten, and increment value by that integer. Let s be the resulting sequence. If s is not the empty string, then:. Let length be the number of characters in s after the spaces were removed.
Let fraction be the result of interpreting s as a base-ten integer, and then dividing that number by 10 length. Increment value by fraction. Add an entry to result consisting of the number given by value and the unit given by unit. Return the list result. This takes into account leap years in the Gregorian calendar. When ASCII digits are used in the date and time syntaxes defined in this section, they express numbers in base ten.
While the formats described here are intended to be subsets of the corresponding ISO formats, this specification defines parsing rules in much more detail than ISO Implementors are therefore encouraged to carefully examine any date parsing libraries before using them to implement the parsing rules described below; ISO libraries might not parse dates and times in exactly the same manner.
Where this specification refers to the proleptic Gregorian calendar , it means the modern Gregorian calendar, extrapolated backwards to year 1. A date in the proleptic Gregorian calendar , sometimes explicitly referred to as a proleptic-Gregorian date , is one that is described using that calendar even if that calendar was not in use at the time or place in question.
The use of the Gregorian calendar as the wire format in this specification is an arbitrary choice resulting from the cultural biases of those involved in the decision. See also the section discussing date, time, and number formats in forms for authors , implementation notes regarding localization of form controls , and the time element. A month consists of a specific proleptic-Gregorian date with no time-zone information and no date information beyond a year and a month.
A string is a valid month string representing a year year and month month if it consists of the following components in the given order:. The rules to parse a month string are as follows. This will return either a year and month, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing. Parse a month component to obtain year and month. If this returns nothing, then fail. If position is not beyond the end of input , then fail.
Return year and month. The rules to parse a month component , given an input string and a position , are as follows. This will return either a year and a month, or nothing. If the collected sequence is not at least four characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer.
Let that number be the year. If year is not a number greater than zero, then fail. Otherwise, move position forwards one character. If the collected sequence is not exactly two characters long, then fail. Let that number be the month. A string is a valid date string representing a year year , month month , and day day if it consists of the following components in the given order:. The rules to parse a date string are as follows. This will return either a date, or nothing. Parse a date component to obtain year , month , and day. Let date be the date with year year , month month , and day day.
Return date. The rules to parse a date component , given an input string and a position , are as follows. This will return either a year, a month, and a day, or nothing. Let maxday be the number of days in month month of year year. Let that number be the day. Return year , month , and day. A string is a valid yearless date string representing a month month and a day day if it consists of the following components in the given order:. In other words, if the month is " 02 ", meaning February, then the day can be 29, as if the year was a leap year. The rules to parse a yearless date string are as follows.
This will return either a month and a day, or nothing. Parse a yearless date component to obtain month and day. Return month and day. The rules to parse a yearless date component , given an input string and a position , are as follows. If the collected sequence is not exactly zero or two characters long, then fail. Let maxday be the number of days in month month of any arbitrary leap year e. A string is a valid time string representing an hour hour , a minute minute , and a second second if it consists of the following components in the given order:.
The second component cannot be 60 or 61; leap seconds cannot be represented. The rules to parse a time string are as follows. This will return either a time, or nothing. Parse a time component to obtain hour , minute , and second. Let time be the time with hour hour , minute minute , and second second.
Return time. The rules to parse a time component , given an input string and a position , are as follows. This will return either an hour, a minute, and a second, or nothing. Let that number be the hour. Let that number be the minute. Let second be 0. Advance position to the next character in input. If position is beyond the end of input , or at the last character in input , or if the next two characters in input starting at position are not both ASCII digits , then fail. Otherwise, interpret the resulting sequence as a base-ten number possibly with a fractional part.
Set second to that number. Return hour , minute , and second. A string is a valid local date and time string representing a date and time if it consists of the following components in the given order:. A string is a valid normalized local date and time string representing a date and time if it consists of the following components in the given order:. The rules to parse a local date and time string are as follows. This will return either a date and time, or nothing. Return date and time.
A string is a valid time-zone offset string representing a time-zone offset if it consists of either:. There is no guarantee that this will remain so forever, however, since time zones are used as political footballs and are thus subject to very whimsical policy decisions. See also the usage notes and examples in the global date and time section below for details on using time-zone offsets with historical times that predate the formation of formal time zones. The rules to parse a time-zone offset string are as follows.
This will return either a time-zone offset, or nothing. Parse a time-zone offset component to obtain timezone hours and timezone minutes. Return the time-zone offset that is timezone hours hours and timezone minutes minutes from UTC. The rules to parse a time-zone offset component , given an input string and a position , are as follows.
This will return either time-zone hours and time-zone minutes, or nothing. Let timezone hours be 0. Let timezone minutes be 0. Let s be the collected sequence. If s is exactly two characters long, then:. Interpret s as a base-ten integer. Let that number be the timezone hours. Let that number be the timezone minutes. If s is exactly four characters long, then:. Interpret the first two characters of s as a base-ten integer. Interpret the last two characters of s as a base-ten integer. Otherwise, fail.
Return timezone hours and timezone minutes. A string is a valid global date and time string representing a date, time, and a time-zone offset if it consists of the following components in the given order:. Time before the formation of time zones must be expressed and interpreted as UT1 times with explicit time zones that approximate the contemporary difference between the appropriate local time and the time observed at the location of Greenwich, London. The following are some examples of dates written as valid global date and time strings.
The rules to parse a global date and time string are as follows. This will return either a time in UTC, with associated time-zone offset information for round-tripping or display purposes, or nothing. If position is beyond the end of input , then fail. Let time be the moment in time at year year , month month , day day , hours hour , minute minute , second second , subtracting timezone hours hours and timezone minutes minutes.
That moment in time is a moment in the UTC time zone. Let timezone be timezone hours hours and timezone minutes minutes from UTC. Return time and timezone. Each week-year in this calendaring system has either 52 or 53 such seven-day periods, as defined below.
The seven-day period starting on the Gregorian date Monday December 29th is defined as week number 1 in week-year Consecutive weeks are numbered sequentially. The week before the number 1 week in a week-year is the last week in the previous week-year, and vice versa. A week-year with a number year has 53 weeks if it corresponds to either a year year in the proleptic Gregorian calendar that has a Thursday as its first day January 1st , or a year year in the proleptic Gregorian calendar that has a Wednesday as its first day January 1st and where year is a number divisible by , or a number divisible by 4 but not by All other week-years have 52 weeks.
The week number of the last day of a week-year with 53 weeks is 53; the week number of the last day of a week-year with 52 weeks is The week-year number of a particular day can be different than the number of the year that contains that day in the proleptic Gregorian calendar. The first week in a week-year y is the week that contains the first Thursday of the Gregorian year y. A string is a valid week string representing a week-year year and week week if it consists of the following components in the given order:.
The rules to parse a week string are as follows. This will return either a week-year number and week number, or nothing.
Let that number be the week. Let maxweek be the week number of the last day of year year. Return the week-year number year and the week number week. Since months and seconds are not comparable a month is not a precise number of seconds, but is instead a period whose exact length depends on the precise day from which it is measured a duration as defined in this specification cannot include months or years, which are equivalent to twelve months. Only durations that describe a specific number of seconds can be described.
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A string is a valid duration string representing a duration t if it consists of either of the following:. The following components:. This, as with a number of other date- and time-related microsyntaxes defined in this specification, is based on one of the formats defined in ISO One or more duration time components , each with a different duration time component scale , in any order; the sum of the represented seconds being equal to the number of seconds in t. A duration time component is a string consisting of the following components:.
One or more ASCII digits , representing a number of time units, scaled by the duration time component scale specified see below to represent a number of seconds. If the duration time component scale specified is 1 i. One of the following characters, representing the duration time component scale of the time unit used in the numeric part of the duration time component :. This is not based on any of the formats in ISO It is intended to be a more human-readable alternative to the ISO duration format. The rules to parse a duration string are as follows. This will return either a duration or nothing.
Let months , seconds , and component count all be zero. Let M-disambiguator be minutes. This flag's other value is months. It is used to disambiguate the "M" unit in ISO durations, which use the same unit for months and minutes. Months are not allowed, but are parsed for future compatibility and to avoid misinterpreting ISO durations that would be valid in other contexts. If position is past the end of input , then fail. Let units be undefined. It will be assigned one of the following values: years , months , weeks , days , hours , minutes , and seconds.
Let next character be undefined. It is used to process characters from the input. If position is past the end of input , then break. Set next character to the character in input pointed to by position. Do not advance position. That is taken care of below. Otherwise, if next character is an ASCII digit , then collect a sequence of code points that are ASCII digits from input given position , interpret the resulting sequence as a base-ten integer, and let N be that number. Set next character to the character in input pointed to by position , and this time advance position to the next character.
If s is the empty string, then fail. Let length be the number of characters in s. Increment N by fraction. Set next character to the character in input pointed to by position , and advance position to the next character. Set units to seconds. If next character is ASCII whitespace , then skip ASCII whitespace within input given position , set next character to the character in input pointed to by position , and advance position to the next character.
Increment component count. Let multiplier be 1. If units is years , multiply multiplier by 12 and set units to months. If units is months , add the product of N and multiplier to months. If units is weeks , multiply multiplier by 7 and set units to days. If units is days , multiply multiplier by 24 and set units to hours. If units is hours , multiply multiplier by 60 and set units to minutes.
If units is minutes , multiply multiplier by 60 and set units to seconds. Forcibly, units is now seconds. Add the product of N and multiplier to seconds. If component count is zero, fail.
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If months is not zero, fail. Return the duration consisting of seconds seconds. The rules to parse a date or time string are as follows. The algorithm will return either a date , a time , a global date and time , or nothing. Set start position to the same position as position. Set the date present and time present flags to true.
If this fails, then set the date present flag to false. Otherwise, if date present is false, set position back to the same position as start position. If the time present flag is true, then parse a time component to obtain hour , minute , and second. If the date present and time present flags are both true, but position is beyond the end of input , then fail. If the date present and time present flags are both true, parse a time-zone offset component to obtain timezone hours and timezone minutes.
If the date present flag is true and the time present flag is false, then let date be the date with year year , month month , and day day , and return date. Otherwise, if the time present flag is true and the date present flag is false, then let time be the time with hour hour , minute minute , and second second , and return time. Otherwise, let time be the moment in time at year year , month month , day day , hours hour , minute minute , second second , subtracting timezone hours hours and timezone minutes minutes, that moment in time being a moment in the UTC time zone; let timezone be timezone hours hours and timezone minutes minutes from UTC; and return time and timezone.
A simple color consists of three 8-bit numbers in the range The rules for parsing simple color values are as given in the following algorithm. This algorithm will return either a simple color or an error. If input is not exactly seven characters long, then return an error. Let result be a simple color. Interpret the second and third characters as a hexadecimal number and let the result be the red component of result. Interpret the fourth and fifth characters as a hexadecimal number and let the result be the green component of result.
Interpret the sixth and seventh characters as a hexadecimal number and let the result be the blue component of result. The rules for serializing simple color values given a simple color are as given in the following algorithm:. Convert the red, green, and blue components in turn to two-digit hexadecimal numbers using ASCII lower hex digits , zero-padding if necessary, and append these numbers to result , in the order red, green, blue.
Return result , which will be a valid lowercase simple color. Some obsolete legacy attributes parse colors in a more complicated manner, using the rules for parsing a legacy color value , which are given in the following algorithm. If input is the empty string, then return an error. If input is an ASCII case-insensitive match for one of the named colors , then return the simple color corresponding to that keyword. CSS2 System Colors are not recognized.
Interpret the second character of input as a hexadecimal digit; let the red component of result be the resulting number multiplied by Interpret the third character of input as a hexadecimal digit; let the green component of result be the resulting number multiplied by Interpret the fourth character of input as a hexadecimal digit; let the blue component of result be the resulting number multiplied by Before we can add these fractions, we'll need to change them so they have the same denominator.
To do that, we'll have to find the LCD , or lowest common denominator, of 4 and 3. It looks like 12 is the smallest number that can be divided by both 3 and 4, so 12 is our LCD. Since 12 is the LCD, it will be the new denominator for our fractions. To change 4 into 12 , we multiplied it by 3. Since the denominator was multiplied by 3 , we'll also multiply the numerator by 3. We changed its denominator to 12 as well. Our old denominator was 3. We multiplied it by 4 to get We'll also multiply the numerator by 4. As usual, the denominator stays the same. We just saw that fractions can only be added when they have the same denominator.
The same thing is true when we're subtracting fractions. Before we can subtract, we'll have to change our fractions so they have the same denominator. Click through the slideshow to learn how to subtract fractions with different denominators. First, we'll change the denominators of both fractions to be the same by finding the lowest common denominator. It looks like 15 is the smallest number that can be divided evenly by 3 and 5 , so 15 is our LCD.
Now we'll change our first fraction. To change the denominator to 15 , we'll multiply the denominator and the numerator by 3. Now let's change the second fraction. As always, the denominator stays the same. Over the last few pages, you've practiced adding and subtracting different kinds of fractions. But some problems will need one extra step. For example, can you add the fractions below? In Introduction to Fractions , you learned about mixed numbers. A mixed number has both a fraction and a whole number. These two numbers look different, but they're actually the same.
This just means the top number is larger than the bottom number. Even though improper fractions look strange, you can add and subtract them just like normal fractions. Mixed numbers aren't easy to add, so you'll have to convert them into improper fractions first. We'll need to convert these mixed numbers to improper fractions. As you learned in Lesson 2 , we'll multiply the whole number, 2 , by the bottom number, 5.
Now, let's add 10 to the numerator, 3. Just like when you add fractions, the denominator stays the same. First, we'll multiply the whole number by the denominator. Next, we'll add 5 to the numerators. Just like last time, the denominator remains the same. Now that we've changed our mixed numbers to improper fractions, we can add like we normally do. As usual, the denominator will stay the same.
Because we started with a mixed number, let's convert this improper fraction back into a mixed number. As you learned in the previous lesson , divide the top number by the bottom number. And the remainder , 1, will become the numerator of the fraction. Want even more practice? Try out a short assessment to test your skills by clicking the link below:. Start Assessment.