project2

/*
 * main.s
 *
 *  Created on: Dec 8, 2020
 *      Author: roger
 */
.text
.global main
.extern printf

main:
    SUB sp, sp, #16
    STR x30, [sp]
    B taylor

taylor:
    LDR x3, =x      //put address of x in x3
    LDR d7, [x3]    //put x in d5
    LDR x3, =n      //put address of n in x3
    LDR x3, [x3]    //put n in x2
    MOV x4, x3      // make the i for the taylor loop = n
taylorloop:
    CMP x4, #0          // if i < 0
    B.LT taylorexit     // then leave the loop to taylorexit
    MOV x2, x4          //input for tpart x2=x4, n=i
    FMOV d2, d7
    B tpart
aftertpart:
    FADD d0, d0, d1
    SUB x4, x4, #1
    B taylorloop

taylorexit:
    LDR x0, =prt_str
    BL printf
    B exit

tpart:                      //finds a part of the taylor series puts in d1, d2=x and x2=n are input, uses d1-d4 and x1-x2
    B exp
tpartafterexp:
    FMOV d5, d1             //save value returned from exp into d3
    SCVTF d2, x2            // convert x2 to a double put in d2
    B fact
tpartafterfact:
    FMOV d6, d1             //save value returned from fact to d4
    FDIV d1, d5, d6         // d1 = d4/d5
    B aftertpart

exp:                        // finds the exponential of d2 to the x2, uses d1 and x1
    MOV x1, #1              // make x1 0
    SCVTF d1, x1            // make d1 using x1 0
    MOV x1, x2              // x1 will be our i in mov
exploop:
    CMP x1, #0              // if i <= 0
    B.LE tpartafterexp      // then move to tpart with d1 as answer
    FMUL d1, d1, d2         // multiply d1 by itself and d2 factx*x
    SUB x1, x1, #1
    B exploop

fact:                       // find the factorial of the value in d2 puts it in d1 uses d1-d3
    FMOV d1, #1.0           // make d1 1
    FMOV d3, #1.0           // make d3 one for comparisons in factloop
    FMOV d4, #1.0
factloop:
    FCMP d4, d2             // if d4 >= d2 which meand d4 >= original number
    B.GE tpartafterfact     // then return to tpartafter
    FADD d4, d4, d3         // d4++
    FMUL d1, d1, d4         // d1 *= d4
    B factloop              // go back to factloop

exit:                       // return to caller
    LDUR x30, [sp]
    ADD sp, sp, #16
    BR x30

.data
    n:
        .quad 1
    x:
        .double 100
    prt_str:
    .ascii "the approximation is %f \n\0"
    .end