REAL_INT_ABS_CONV : conv

SYNOPSIS

Conversion to produce absolute value of an integer literal of type :real.

DESCRIPTION

The call REAL_INT_ABS_CONV `abs c`, where c is an integer literal of type :real, returns the theorem |- abs c = d where d is the canonical integer literal that is equal to c's absolute value. The literal c may be of the form &n or -- &n (with nonzero n in the latter case) and the result will be of the same form.

FAILURE CONDITIONS

Fails if applied to a term that is not the negation of one of the permitted forms of integer literal of type :real.

EXAMPLE

  # REAL_INT_ABS_CONV `abs(-- &42)`;;
  val it : thm = |- abs (-- &42) = &42

COMMENTS

The related function REAL_RAT_ABS_CONV subsumes this functionality, also applying to rational literals. Unless the restriction to integers is desired or a tiny efficiency difference matters, it should be used in preference.