NUM_PRE_CONV : term -> thm
Proves what the cutoff predecessor of a natural number numeral is.
If n is a numeral (e.g. 0, 1, 2, 3,...), then
NUM_PRE_CONV `PRE n` returns the theorem:
where s is the numeral that denotes the cutoff predecessor of the
natural number denoted by n (that is, the result of subtracting 1 from it, or
zero if it is already zero).
- FAILURE CONDITIONS
NUM_PRE_CONV tm fails if tm is not of the form `PRE n`, where n is a
# NUM_PRE_CONV `PRE 0`;;
val it : thm = |- PRE 0 = 0
# NUM_PRE_CONV `PRE 12345`;;
val it : thm = |- PRE 12345 = 12344
- SEE ALSO
NUM_ADD_CONV, NUM_DIV_CONV, NUM_EQ_CONV, NUM_EVEN_CONV, NUM_EXP_CONV,
NUM_FACT_CONV, NUM_GE_CONV, NUM_GT_CONV, NUM_LE_CONV, NUM_LT_CONV,
NUM_MAX_CONV, NUM_MIN_CONV, NUM_MOD_CONV, NUM_MULT_CONV, NUM_ODD_CONV,
NUM_REDUCE_CONV, NUM_RED_CONV, NUM_REL_CONV, NUM_SUB_CONV, NUM_SUC_CONV.