1

I don't know why this code doesn't work:

\documentclass[11pt]{article}
\usepackage{fullpage}
\usepackage{amsfonts}
\usepackage[utf8]{inputenc}
\usepackage{amsthm}
\newtheorem{theorem}{Teorema}
\theoremstyle{definition}
\newtheorem{definition}{Definição}
\begin{document}

\begin{definition}

Um conjunto $H$ com uma operação binária associativa é chamado de semigrupo.

\end{definition}

\begin{definition}

Um semigrupo $H\subset \mathbb{N}$ é chamado de numérico quando $0\in H$, $L=\mathbb{N}-H$ é finito e $1\in L$. Os elementos $1=l_1\lt l_2\ldots\lt l_g$ de $L$ são chamados de lacunas de $H$ e os elementos $0=n_0\lt n_1\lt\ldots$ de $H$ são chamados de não-lacunas de $H$. A quantidade de lacunas de $H$ é chamada de gênero de $H$.

\end{definition}

\begin{definition}

Um semigrupo numérico $H$ é chamado de hiperelíptico quando $n_1=2\in H$.

\end{definition}

\end{document}

Log:

! Undefined control sequence.
l.19 ... finito e $1\in L$. Os elementos $1=l_1\lt
l_2\ldots\lt l_g$ de $L$ ...
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
! Undefined control sequence.
l.19 ...in L$. Os elementos $1=l_1\lt l_2\ldots\lt
l_g$ de $L$ são chamados...

It's something to do with the language?

Thanks

  • There is no \lt command as far as I know. Use < instead if you mean that symbol. – user31729 Sep 19 '14 at 4:09
  • At several places \lt is used inside math. What it is supposed to mean? – Heiko Oberdiek Sep 19 '14 at 4:10
  • 1
  • @user108205: I retagged your question, since it's not connected to languages but to an error due to an unknown macro named \lt – user31729 Sep 19 '14 at 4:29
  • 1
    @Aradnix Thank you very much, I didn't know it! – user108205 Sep 23 '14 at 20:31
1

I think, \lt should mean less than, there is no such command however, as far as I know.

It's easy to define such a command with this meaning, if needed:

\newcommand{\lt}{\ensuremath{<}}%

There are some commands called \le and \ge meaning <= etc.

In addition, if needed, a \gt can be defined accordingly:

\newcommand{\gt}{\ensuremath{>}}%

\documentclass[11pt]{article}
\usepackage{fullpage}
\usepackage{amsfonts}
\usepackage[utf8]{inputenc}
\usepackage{amsthm}
\newtheorem{theorem}{Teorema}
\theoremstyle{definition}
\newtheorem{definition}{Definição}

\newcommand{\lt}{\ensuremath{<}}%
\begin{document}

\begin{definition}

Um conjunto $H$ com uma operação binária associativa é chamado de semigrupo.

\end{definition}

\begin{definition}

Um semigrupo $H\subset \mathbb{N}$ é chamado de numérico quando $0\in H$, $L=\mathbb{N}-H$ é finito e $1\in L$. Os elementos $1=l_1 \lt l_2\ldots \lt l_g$ de $L$ são chamados de lacunas de $H$ e os elementos $0=n_0\lt n_1\lt\ldots$ de $H$ são chamados de não-lacunas de $H$. A quantidade de lacunas de $H$ é chamada de gênero de $H$.

\end{definition}

\begin{definition}

Um semigrupo numérico $H$ é chamado de hiperelíptico quando $n_1=2\in H$.

\end{definition}

\end{document}

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