Routines 
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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.


to_power  3851  RST $28  X, Y  
3852  DEFB $01  exchange: Y, X  
3853  DEFB $31  duplicate: Y, X, X  
3854  DEFB $30  f_not: Y, X, (1/0)  
3855  DEFB $00  jump_true to XIS0: Y, X  
3856  DEFB $07  
The jump is made if X=0, otherwise EXP (Y*LN X) is formed.


3857  DEFB $25  ln: Y, LN X  
Giving report A if X is negative.


3858  DEFB $04  multiply: Y*LN X  
3859  DEFB $38  end_calc  
385A  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  385D  DEFB $02  delete: Y  
385E  DEFB $31  duplicate: Y, Y  
385F  DEFB $30  f_not: Y, (1/0)  
3860  DEFB $00  jump_true to ONE: Y  
3861  DEFB $09  
The jump is made if X=0 and Y=0, otherwise proceed.


3862  DEFB $A0  stk_zero: Y, 0  
3863  DEFB $01  exchange: 0, Y  
3864  DEFB $37  greater_0: 0, (1/0)  
3865  DEFB $00  jump_true to LAST: 0  
3866  DEFB $06  
The jump is made if X=0 and Y is positive, otherwise proceed.


3867  DEFB $A1  stk_one: 0, 1  
3868  DEFB $01  exchange: 1, 0  
3869  DEFB $05  division: Exit via division as dividing by zero gives 'arithmetic overflow'.  
The result is to be 1 for the operation.


ONE  386A  DEFB $02  delete:   
386B  DEFB $A1  stk_one: 1  
Now return with the 'last value' on the stack being 0**Y.


LAST  386C  DEFB $38  end_calc: (1/0)  
386D  RET  Finished: 'last value' is 0 or 1. 
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