Introductory Examples of the Use of NI, ELI and PI Indicators in the Nemeth Code

The braille examples on this page are intended to be shown in both ASCII braille and simulated braille dots but if you don't have a Duxbury braille font installed, the ASCII will just be repeated. Some of the examples also use one of many display options based on dotless braille. References to numbered rules, etc. are to the 1972 Revision of the Nemeth Code Book.


The examples on this page are all linked to the corresponding rules of useage so you can start with this page.

1. The Numeric Indicator (NI) and the Letter Indicator (LI)

Although the NI and the ELI might be expected to have analogous purposes, the respective rules for their use are actually quite different.

In literary expressions.

EXAMPLE 1.1. According to Rule IV, Section 26b(10), a hyphenated item such as the "1-a" in "Exercise 1-a" (assumed to be followed by a space or punctuation), is transcribed according to the Nemeth code as

The NI is needed before the numeral to aid in recognizing alignment of the lower-cell numeral preceded by a space and also to ensure that it not be read as a punctuation mark or lower-sign contraction. The ELI is needed before the symbol following the hyphen to ensure that it is recognized as a letter rather than a single-letter contraction for a word. (The ELI when used for this purpose has been called the LI here.)

EXAMPLE 1.2. According to Rule II, Section 11d(3), a hyphenated item such as the "a-1" in "Exercise a-1", is transcribed according to the Nemeth code as

Example 1.2 differs from the previous example in that the NI is not needed after the hyphen because the number is no longer preceded by a space and because there is math context prior to the hyphen. (This means that in the unlikely situation of another punctuation mark following the hyphen, an intervening Punctuation Indicator would be required.) The LI is needed because the symbol is preceded by a space and in contact with the following hyphen.

In mathematical expressions.

An LI is never used in mathematical expressions to distinguish a symbol even if a symbol begins the expression; an NI is used if a number begins a mathematical expression because of its necessarily being preceded by a space or if a number embedded in a mathematical expression happens to be preceded by a space. (However, the rules for the use of the ELI with symbols set in special typeforms and the rules for the use of the TNI with numbers set in special typeforms do not depend on context. See also examples below.)

2. The Numeric Indicator (NI) and the Punctuation Indicator (PI)

A definite point of time or time-of-day is transcribed differently in Nemeth than it is in literary braille because of the PI. If you've looked at the algebra example on the page comparing Nemeth with HTML, you will appreciate that time-of-day is a worst case scenario for the Nemeth code and the high proportion of indicators is an unavoidable side effect of the rules that make Nemeth so compact in more important situations. [Cf. Rule II, Section 11d(2).]

Clock times

EXAMPLE 2.1. The time 3:33 is transcribed as

The colon requires a preceding PI in order to distinguish it from a numeral in this potentially math context. The number following the colon thus requires a preceding NI in order to restore mathematical context since the effect of a PI is not restricted to just one cell. The second digit does not need a second NI because the effect of an NI is the entire number so an additional NI (or TNI) is only used before the first digit of a number unless there is a transition in typeforms between the digits.

EXAMPLE 2.2 "Time to go home" is sometimes jokingly called beer:30 which is transcribed as

No PI is needed before the colon in Example 2.2 since it is preceded by ordinary text.

Time periods using clock-times (includes LI)

The next four examples below illustrate the transcription of time periods shown by using a hyphen between two times. Since these examples don't require any rules not used in the previous ones, you might want to try transcribing them yourself before you look at the answers.

EXAMPLE 2.3. The time period 2:30-3:30 is transcribed as

EXAMPLE 2.4. The vague or humorous time period 2:30-late is transcribed as

Example 2.3 emphasizes that Nemeth has no special indicator for the switch back to words (or other text) since that is the default.

EXAMPLE 2.5. The vague time period 2:30-x is transcribed as

Comparison of Example 2.5 with Example 2.4 shows why the LI is needed to ensure that the letter is recognized as a letter rather than a contraction for a word.

EXAMPLE 2.6. The vague time period now-2:30 is transcribed as

The NI is required before the number following the hyphen because of the preceding literary context.

3. Comparing Indicator functions: NI, LI, TNI, and ELI

A required NI is used before any number (no matter which digits nor how many) whereas the use of the LI depends on the particular symbol: an LI is only ever used with single-letter symbols and multiple-letter symbols that correspond to braille short-form words. However, the scopes of both the NI and the LI are the entire number or entire symbol.

By contrast, although the scope of the TNI needed for a number individually set in a special type form is also the entire number, the scope of an ELI needed for a symbol in special type is one letter even if an entire multi-letter symbol is set in the same special type. These examples show numbers and symbols embedded in an overall literary context.

The NI versus the LI

The number requires an NI because of the preceding space and to avoid ambiguity in a literary context. The symbol requires an LI because of the literary context to indicate that it is not a short-form word.

The number requires one preceding NI for the same reasons as the previous example. The symbol ab requires a preceding LI in this literary context since the same letter sequence is also used as a braille short-form word. The symbol xx does not require a preceding LI since its letter sequence does not correspond to any braille short-form word.

The TNI versus the ELI

The number requires a TNI and the symbol requires an ELI because of the boldface type-form indicators.

The number requires a single NI following the bold-face type-form indicator since the scope of a type-form indicator before a number is the entire number. Both letters in both symbols require boldface type-form indicators followed by an ELI since the scope of a type-form indicator before a letter is one character; this syntax serves to distinguish a symbol from a word so an otherwise necessary LI is not used in this situation.

4. The LI and Grouping Symbols

  1. Case one is (x, y) = (z, boy). Symbol z does not require an LI in the preceding sentence.
  2. Case two is (x, y) = (boy, z). Symbol z requires an LI in the preceding sentence.
  3. Case three is (z, boy) = (x, y). Symbol z requires an LI in the preceding sentence.
  4. Case four is (boy, z) = (x, y). Symbol z does not require an LI in the preceding sentence.
The construct (x, y) is an example of an enclosed list and an LI is never used in an enclosed list. However the constructs (boy, z) and (z, boy) are not enclosed lists because of the presence of the ordinary word. The use or non-use of the LI thus follows from the general rules for the use of the LI.

According to Rule IV, Section 28, if a mathematical symbol "is in direct contact with only its opening or only its closing grouping sign, the English-letter indicator must be used ... or must not be used ... as though the grouping signs were not present [if the grouping sign is unembellished]."

In Case one no LI is required since the previous context (ignoring the parenthesis) is mathematical. In Cases two and three an LI is required since both the previous and following contexts are literary. (The following parenthesis in Case two and the preceding one in Case three are both ignored.) In Case four no LI is required since the following context (ignoring the parenthesis) is mathematical.

The first three cases make immediate sense to the print reader who naturally expects the current context to continue so the LI in Cases two and three serve as a warning. However, the same cell is used for the LI as for the subscript indicator so the use of the LI could also be interpreted as indicating a left subscript and this isn't resolved until reading the next character or so. However, the more likely interpretation is the correct one which, given the elegance of the Nemeth code, is not surprising. In Case four there is a corresponding moment where the reader might not be certain whether the z, unpreceded by an LI, is a single-letter word or a mathematical symbol. This too is quickly resolved. Mathematical symbols before a comparison sign don't use the LI; common sense avoids the need for ad hoc rules.

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This page was first posted on February 18, 2002 and last modified on February 27, 2002.

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