# HG changeset patch # User paulson # Date 1037785400 -3600 # Node ID e03747c2ca58406726a9afb63f8a57929a501fd5 # Parent 2cf506c09946eaa8b88313f65380a0ceb807a905 textual tweak diff -r 2cf506c09946 -r e03747c2ca58 doc-src/TutorialI/Inductive/even-example.tex --- a/doc-src/TutorialI/Inductive/even-example.tex Tue Nov 19 10:41:20 2002 +0100 +++ b/doc-src/TutorialI/Inductive/even-example.tex Wed Nov 20 10:43:20 2002 +0100 @@ -186,8 +186,9 @@ \ 1.\ n\ \isasymin \ even\isanewline \ 2.\ \isasymAnd na.\ \isasymlbrakk na\ \isasymin \ even;\ n\ \isasymin \ even\isasymrbrakk \ \isasymLongrightarrow \ n\ \isasymin \ even% \end{isabelle} -The first one is hopeless. Rule inductions involving -non-trivial terms usually fail. How to deal with such situations +The first one is hopeless. Rule induction on +a non-variable term discards information, and usually fails. +How to deal with such situations in general is described in {\S}\ref{sec:ind-var-in-prems} below. In the current case the solution is easy because we have the necessary inverse, subtraction: