Spectrum ROM: Routine at 14417

The address of this routine is found in the table of addresses. It is called indirectly via fp_calc_2, and the routine at sqr continues here.

This subroutine performs the binary operation of raising the first number, X, to the power of the second number, Y.

The subroutine treats the result X**Y as being equivalent to EXP (Y*LN X). It returns this value unless X is zero, in which case it returns 1 if Y is also zero (0**0=1), returns zero if Y is positive, and reports arithmetic overflow if Y is negative.

The address of this routine is found in the table of addresses. It is called indirectly via fp_calc_2, and the routine at sqr continues here. This subroutine performs the binary operation of raising the first number, X, to the power of the second number, Y. The subroutine treats the result X*Y as being equivalent to EXP (YLN X). It returns this value unless X is zero, in which case it returns 1 if Y is also zero (0**0=1), returns zero if Y is positive, and reports arithmetic overflow if Y is negative.
to_power	14417	RST 40	X, Y
	14418	DEFB 1	exchange: Y, X
	14419	DEFB 49	duplicate: Y, X, X
	14420	DEFB 48	f_not: Y, X, (1/0)
	14421	DEFB 0	jump_true to XIS0: Y, X
	14422	DEFB 7	jump_true to XIS0: Y, X
The jump is made if X=0, otherwise EXP (Y*LN X) is formed.
	14423	DEFB 37	ln: Y, LN X
Giving report A if X is negative.
	14424	DEFB 4	multiply: Y*LN X
	14425	DEFB 56	end_calc
	14426	JP exp	Exit via exp to form EXP (Y*LN X).
The value of X is zero so consider the three possible cases involved.
XIS0	14429	DEFB 2	delete: Y
	14430	DEFB 49	duplicate: Y, Y
	14431	DEFB 48	f_not: Y, (1/0)
	14432	DEFB 0	jump_true to ONE: Y
	14433	DEFB 9	jump_true to ONE: Y
The jump is made if X=0 and Y=0, otherwise proceed.
	14434	DEFB 160	stk_zero: Y, 0
	14435	DEFB 1	exchange: 0, Y
	14436	DEFB 55	greater_0: 0, (1/0)
	14437	DEFB 0	jump_true to LAST: 0
	14438	DEFB 6	jump_true to LAST: 0
The jump is made if X=0 and Y is positive, otherwise proceed.
	14439	DEFB 161	stk_one: 0, 1
	14440	DEFB 1	exchange: 1, 0
	14441	DEFB 5	division: Exit via division as dividing by zero gives 'arithmetic overflow'.
The result is to be 1 for the operation.
ONE	14442	DEFB 2	delete: -
	14443	DEFB 161	stk_one: 1
Now return with the 'last value' on the stack being 0**Y.
LAST	14444	DEFB 56	end_calc: (1/0)
	14445	RET	Finished: 'last value' is 0 or 1.