7296 - rough support for printing floats
No rounding yet, and we have a blunt way to decide when to start truncating.
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# print out floats in decimal
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# https://research.swtch.com/ftoa
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#
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# Basic idea:
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# Ignoring sign, floating point numbers are represented as 1.mantissa * 2^exponent
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# Therefore, to print a float in decimal, we need to:
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# - compute its value without decimal point
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# - convert to an array of decimal digits
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# - print out the array while inserting the decimal point appropriately
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#
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# Basic complication: the computation generates numbers larger than an int can
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# hold. We need a way to represent big ints.
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#
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# Key insight: use a representation for big ints that's close to what we need
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# anyway, an array of decimal digits.
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#
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# Style note: we aren't creating a big int library here. The only operations
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# we need are halving and doubling. Following the link above, it seems more
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# comprehensible to keep these operations inlined so that we can track the
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# position of the decimal point with dispatch.
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#
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# This approach turns out to be fast enough for most purposes.
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# Optimizations, however, get wildly more complex.
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fn test-print-float-decimal-approximate-normal {
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var screen-on-stack: screen
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var screen/esi: (addr screen) <- address screen-on-stack
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initialize-screen screen, 5, 0x20 # 32 columns should be more than enough
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# 0.5
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var half/xmm0: float <- rational 1, 2
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print-float-decimal-approximate screen, half, 3
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check-screen-row screen, 1, "0.5 ", "F - test-print-float-decimal-approximate-normal 0.5"
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# 0.25
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clear-screen screen
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var quarter/xmm0: float <- rational 1, 4
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print-float-decimal-approximate screen, quarter, 3
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check-screen-row screen, 1, "0.25 ", "F - test-print-float-decimal-approximate-normal 0.25"
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# 0.75
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clear-screen screen
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var three-quarters/xmm0: float <- rational 3, 4
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print-float-decimal-approximate screen, three-quarters, 3
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check-screen-row screen, 1, "0.75 ", "F - test-print-float-decimal-approximate-normal 0.75"
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# 0.125
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clear-screen screen
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var eighth/xmm0: float <- rational 1, 8
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print-float-decimal-approximate screen, eighth, 3
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check-screen-row screen, 1, "0.125 ", "F - test-print-float-decimal-approximate-normal 0.1"
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# 0.0625; start using scientific notation
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clear-screen screen
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var sixteenth/xmm0: float <- rational 1, 0x10
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print-float-decimal-approximate screen, sixteenth, 3
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check-screen-row screen, 1, "6.25e-2 ", "F - test-print-float-decimal-approximate-normal 0.625"
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}
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# print whole integers without decimals
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fn test-print-float-decimal-approximate-integer {
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var screen-on-stack: screen
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var screen/esi: (addr screen) <- address screen-on-stack
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initialize-screen screen, 5, 0x20 # 32 columns should be more than enough
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# 1
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var one-f/xmm0: float <- rational 1, 1
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print-float-decimal-approximate screen, one-f, 3
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check-screen-row screen, 1, "1 ", "F - test-print-float-decimal-approximate-integer 1"
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# 2
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clear-screen screen
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var two-f/xmm0: float <- rational 2, 1
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print-float-decimal-approximate screen, two-f, 3
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check-screen-row screen, 1, "2 ", "F - test-print-float-decimal-approximate-integer 2"
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# 10
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clear-screen screen
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var ten-f/xmm0: float <- rational 0xa, 1
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print-float-decimal-approximate screen, ten-f, 3
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check-screen-row screen, 1, "10 ", "F - test-print-float-decimal-approximate-integer 10"
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# -10
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clear-screen screen
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var minus-ten-f/xmm0: float <- rational -0xa, 1
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print-float-decimal-approximate screen, minus-ten-f, 3
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check-screen-row screen, 1, "-10 ", "F - test-print-float-decimal-approximate-integer -10"
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# 100,000 - start using scientific notation
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clear-screen screen
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var hundred-thousand/eax: int <- copy 0x186a0
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var hundred-thousand-f/xmm0: float <- convert hundred-thousand
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print-float-decimal-approximate screen, hundred-thousand-f, 3
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check-screen-row screen, 1, "1.00e5 ", "F - test-print-float-decimal-approximate-integer 100,000"
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}
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fn test-print-float-decimal-approximate-zero {
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var screen-on-stack: screen
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var screen/esi: (addr screen) <- address screen-on-stack
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initialize-screen screen, 5, 0x20 # 32 columns should be more than enough
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var zero: float
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print-float-decimal-approximate screen, zero, 3
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check-screen-row screen, 1, "0 ", "F - test-print-float-decimal-approximate-zero"
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}
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fn test-print-float-decimal-approximate-negative-zero {
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var screen-on-stack: screen
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var screen/esi: (addr screen) <- address screen-on-stack
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initialize-screen screen, 5, 0x20 # 32 columns should be more than enough
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var n: int
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copy-to n, 0x80000000
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var negative-zero/xmm0: float <- reinterpret n
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print-float-decimal-approximate screen, negative-zero, 3
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check-screen-row screen, 1, "-0 ", "F - test-print-float-decimal-approximate-negative-zero"
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}
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fn test-print-float-decimal-approximate-infinity {
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var screen-on-stack: screen
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var screen/esi: (addr screen) <- address screen-on-stack
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initialize-screen screen, 5, 0x20 # 32 columns should be more than enough
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var n: int
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# 0|11111111|00000000000000000000000
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# 0111|1111|1000|0000|0000|0000|0000|0000
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copy-to n, 0x7f800000
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var infinity/xmm0: float <- reinterpret n
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print-float-decimal-approximate screen, infinity, 3
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check-screen-row screen, 1, "Inf ", "F - test-print-float-decimal-approximate-infinity"
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}
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fn test-print-float-decimal-approximate-negative-infinity {
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var screen-on-stack: screen
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var screen/esi: (addr screen) <- address screen-on-stack
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initialize-screen screen, 5, 0x20 # 32 columns should be more than enough
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var n: int
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copy-to n, 0xff800000
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var negative-infinity/xmm0: float <- reinterpret n
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print-float-decimal-approximate screen, negative-infinity, 3
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check-screen-row screen, 1, "-Inf ", "F - test-print-float-decimal-approximate-negative-infinity"
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}
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fn test-print-float-decimal-approximate-not-a-number {
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var screen-on-stack: screen
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var screen/esi: (addr screen) <- address screen-on-stack
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initialize-screen screen, 5, 0x20 # 32 columns should be more than enough
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var n: int
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copy-to n, 0xffffffff # exponent must be all 1's, and mantissa must be non-zero
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var negative-infinity/xmm0: float <- reinterpret n
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print-float-decimal-approximate screen, negative-infinity, 3
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check-screen-row screen, 1, "NaN ", "F - test-print-float-decimal-approximate-not-a-number"
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}
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# 'precision' controls the maximum width past which we resort to scientific notation
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fn print-float-decimal-approximate screen: (addr screen), n: float, precision: int {
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# - special names
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var bits/eax: int <- reinterpret n
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compare bits, 0
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{
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break-if-!=
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print-string screen, "0"
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return
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}
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compare bits, 0x80000000
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{
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break-if-!=
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print-string screen, "-0"
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return
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}
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compare bits, 0x7f800000
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{
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break-if-!=
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print-string screen, "Inf"
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return
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}
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compare bits, 0xff800000
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{
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break-if-!=
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print-string screen, "-Inf"
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return
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}
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var exponent/ecx: int <- copy bits
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exponent <- shift-right 0x17 # 23 bits of mantissa
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exponent <- and 0xff
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exponent <- subtract 0x7f
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compare exponent, 0x80
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{
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break-if-!=
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print-string screen, "NaN"
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return
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}
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# - regular numbers
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var sign/edx: int <- copy bits
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sign <- shift-right 0x1f
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{
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compare sign, 1
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break-if-!=
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print-string screen, "-"
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}
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# v = 1.mantissa (in base 2) << 0x17
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var v/ebx: int <- copy bits
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v <- and 0x7fffff
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v <- or 0x00800000 # insert implicit 1
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# e = exponent - 0x17
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var e/ecx: int <- copy exponent
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e <- subtract 0x17 # move decimal place from before mantissa to after
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# initialize buffer with decimal representation of v
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# unlike https://research.swtch.com/ftoa, no ascii here
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var buf-storage: (array byte 0x7f)
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var buf/edi: (addr array byte) <- address buf-storage
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#? print-int32-decimal 0, v
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#? print-string 0, "\n"
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var n/eax: int <- decimal-digits v, buf
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#? dump-digits buf, n, "init"
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# I suspect we can do without reversing, but we'll follow https://research.swtch.com/ftoa
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# closely for now.
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reverse-digits buf, n
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#? dump-digits buf, n, "reverse"
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# loop if e > 0
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{
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compare e, 0
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break-if-<=
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n <- double-array-of-decimal-digits buf, n
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#? dump-digits buf, n, "double"
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e <- decrement
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loop
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}
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var dp/edx: int <- copy n
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# loop if e < 0
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{
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compare e, 0
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break-if->=
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n, dp <- halve-array-of-decimal-digits buf, n, dp
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#? print-int32-decimal 0, dp
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#? print-string 0, ", "
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#? dump-digits buf, n, "halve"
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e <- increment
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loop
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}
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print-float-buffer screen, buf, n, dp, precision
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}
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# store the decimal digits of 'n' into 'buf', units first
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# n must be positive
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fn decimal-digits n: int, _buf: (addr array byte) -> _/eax: int {
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var buf/edi: (addr array byte) <- copy _buf
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var i/ecx: int <- copy 0
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var curr/eax: int <- copy n
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var curr-byte/edx: int <- copy 0
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{
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compare curr, 0
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break-if-=
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curr, curr-byte <- integer-divide curr, 0xa
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var dest/ebx: (addr byte) <- index buf, i
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copy-byte-to *dest, curr-byte
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i <- increment
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loop
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}
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return i
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}
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fn reverse-digits _buf: (addr array byte), n: int {
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var buf/esi: (addr array byte) <- copy _buf
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var left/ecx: int <- copy 0
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var right/edx: int <- copy n
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right <- decrement
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{
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compare left, right
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break-if->=
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{
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var l-a/ecx: (addr byte) <- index buf, left
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var r-a/edx: (addr byte) <- index buf, right
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var l/ebx: byte <- copy-byte *l-a
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var r/eax: byte <- copy-byte *r-a
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copy-byte-to *l-a, r
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copy-byte-to *r-a, l
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}
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left <- increment
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right <- decrement
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loop
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}
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}
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# debug helper
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fn dump-digits _buf: (addr array byte), count: int, msg: (addr array byte) {
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var buf/edi: (addr array byte) <- copy _buf
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var i/ecx: int <- copy 0
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print-string 0, msg
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print-string 0, ": "
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{
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compare i, count
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break-if->=
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var curr/edx: (addr byte) <- index buf, i
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var curr-byte/eax: byte <- copy-byte *curr
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var curr-int/eax: int <- copy curr-byte
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print-int32-decimal 0, curr-int
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print-string 0, " "
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break-if-=
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i <- increment
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loop
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}
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print-string 0, "\n"
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}
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fn double-array-of-decimal-digits _buf: (addr array byte), _n: int -> _/eax: int {
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var buf/edi: (addr array byte) <- copy _buf
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# initialize delta
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var delta/edx: int <- copy 0
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{
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var curr/ebx: (addr byte) <- index buf, 0
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var tmp/eax: byte <- copy-byte *curr
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compare tmp, 5
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break-if-<
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delta <- copy 1
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}
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# loop
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var x/eax: int <- copy 0
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var i/ecx: int <- copy _n
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i <- decrement
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{
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compare i, 0
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break-if-<=
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# x += 2*buf[i]
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{
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var tmp/ecx: (addr byte) <- index buf, i
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var tmp2/ecx: byte <- copy-byte *tmp
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x <- add tmp2
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x <- add tmp2
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}
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# x, buf[i+delta] = x/10, x%10
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{
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var dest-index/ecx: int <- copy i
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dest-index <- add delta
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var dest/edi: (addr byte) <- index buf, dest-index
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var next-digit/edx: int <- copy 0
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x, next-digit <- integer-divide x, 0xa
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copy-byte-to *dest, next-digit
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}
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#
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i <- decrement
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loop
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}
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# final patch-up
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var n/eax: int <- copy _n
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compare delta, 1
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{
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break-if-!=
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var curr/ebx: (addr byte) <- index buf, 0
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var one/edx: int <- copy 1
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copy-byte-to *curr, one
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n <- increment
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}
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return n
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}
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fn halve-array-of-decimal-digits _buf: (addr array byte), _n: int, _dp: int -> _/eax: int, _/edx: int {
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var buf/edi: (addr array byte) <- copy _buf
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var n/eax: int <- copy _n
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var dp/edx: int <- copy _dp
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# initialize one side
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{
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# if buf[n-1]%2 == 0, break
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var right-index/ecx: int <- copy n
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right-index <- decrement
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var right-a/ecx: (addr byte) <- index buf, right-index
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var right/ecx: byte <- copy-byte *right-a
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var right-int/ecx: int <- copy right
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var remainder/edx: int <- copy 0
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{
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var dummy/eax: int <- copy 0
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dummy, remainder <- integer-divide right-int, 2
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}
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compare remainder, 0
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break-if-=
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# buf[n] = 0
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var next-a/ecx: (addr byte) <- index buf, n
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var zero/edx: byte <- copy 0
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copy-byte-to *next-a, zero
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# n++
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n <- increment
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}
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# initialize the other
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var delta/ebx: int <- copy 0
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var x/esi: int <- copy 0
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{
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# if buf[0] >= 2, break
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var left/ecx: (addr byte) <- index buf, 0
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var src/ecx: byte <- copy-byte *left
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compare src, 2
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break-if->=
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# delta, x = 1, buf[0]
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delta <- copy 1
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x <- copy src
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# n--
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n <- decrement
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# dp--
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dp <- decrement
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}
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# loop
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var i/ecx: int <- copy 0
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{
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compare i, n
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break-if->=
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# x = x*10 + buf[i+delta]
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{
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var ten/edx: int <- copy 0xa
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x <- multiply ten
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var src-index/edx: int <- copy i
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src-index <- add delta
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var src-a/edx: (addr byte) <- index buf, src-index
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var src/edx: byte <- copy-byte *src-a
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x <- add src
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}
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# buf[i], x = x/2, x%2
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{
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var quotient/eax: int <- copy 0
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var remainder/edx: int <- copy 0
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quotient, remainder <- integer-divide x, 2
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x <- copy remainder
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var dest/edx: (addr byte) <- index buf, i
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copy-byte-to *dest, quotient
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}
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#
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i <- increment
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loop
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}
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return n, dp
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}
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fn print-float-buffer screen: (addr screen), _buf: (addr array byte), n: int, dp: int, precision: int {
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var buf/edi: (addr array byte) <- copy _buf
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#? print-int32-hex 0, dp
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#? print-string 0, "\n"
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{
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compare dp, 0
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break-if->=
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print-float-buffer-in-scientific-notation screen, buf, n, dp, precision
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return
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}
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{
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var dp2/eax: int <- copy dp
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compare dp2, precision
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break-if-<
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print-float-buffer-in-scientific-notation screen, buf, n, dp, precision
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return
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}
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{
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compare dp, 0
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break-if-!=
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print-string screen, "0"
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}
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var i/eax: int <- copy 0
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{
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compare i, n
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break-if->=
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# print '.' if necessary
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compare i, dp
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{
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break-if-!=
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print-string screen, "."
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}
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var curr-a/ecx: (addr byte) <- index buf, i
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var curr/ecx: byte <- copy-byte *curr-a
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curr <- add 0x30 # '0'
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var curr-grapheme/ecx: grapheme <- copy curr
|
||||
print-grapheme screen, curr-grapheme
|
||||
i <- increment
|
||||
loop
|
||||
}
|
||||
}
|
||||
|
||||
fn print-float-buffer-in-scientific-notation screen: (addr screen), _buf: (addr array byte), n: int, dp: int, precision: int {
|
||||
var buf/edi: (addr array byte) <- copy _buf
|
||||
var i/eax: int <- copy 0
|
||||
{
|
||||
compare i, n
|
||||
break-if->=
|
||||
compare i, precision
|
||||
break-if->=
|
||||
compare i, 1
|
||||
{
|
||||
break-if-!=
|
||||
print-string screen, "."
|
||||
}
|
||||
var curr-a/ecx: (addr byte) <- index buf, i
|
||||
var curr/ecx: byte <- copy-byte *curr-a
|
||||
curr <- add 0x30 # '0'
|
||||
var curr-grapheme/ecx: grapheme <- copy curr
|
||||
print-grapheme screen, curr-grapheme
|
||||
#
|
||||
i <- increment
|
||||
loop
|
||||
}
|
||||
print-string screen, "e"
|
||||
decrement dp
|
||||
print-int32-decimal screen, dp
|
||||
}
|
||||
|
||||
## helper
|
||||
|
||||
# like check-strings-equal, except array sizes don't have to match
|
||||
fn check-buffer-contains _buf: (addr array byte), _contents: (addr array byte), msg: (addr array byte) {
|
||||
var buf/esi: (addr array byte) <- copy _buf
|
||||
var contents/edi: (addr array byte) <- copy _contents
|
||||
var a/eax: boolean <- string-starts-with? buf, contents
|
||||
check-true a, msg
|
||||
var len/ecx: int <- length contents
|
||||
var len2/eax: int <- length buf
|
||||
compare len, len2
|
||||
break-if-=
|
||||
var c/eax: (addr byte) <- index buf, len
|
||||
var d/eax: byte <- copy-byte *c
|
||||
var e/eax: int <- copy d
|
||||
check-ints-equal e, 0, msg
|
||||
}
|
||||
|
||||
fn test-check-buffer-contains {
|
||||
var arr: (array byte 4)
|
||||
var a/esi: (addr array byte) <- address arr
|
||||
var b/eax: (addr byte) <- index a, 0
|
||||
var c/ecx: byte <- copy 0x61 # 'a'
|
||||
copy-byte-to *b, c
|
||||
check-buffer-contains a, "a", "F - test-check-buffer-contains"
|
||||
check-buffer-contains "a", "a", "F - test-check-buffer-contains/null" # no null check when arrays have same length
|
||||
}
|
||||
|
||||
#? fn main -> _/ebx: int {
|
||||
#? run-tests
|
||||
#? #? test-print-float-decimal-approximate-integer
|
||||
#? #? test-print-float-decimal-approximate-normal
|
||||
#? return 0
|
||||
#? }
|
|
@ -130,6 +130,7 @@ compare var, n => "81 7/subop/compare *(ebp+" var.stack-offse
|
|||
compare *var/reg, n => "81 7/subop/compare *" reg " " n "/imm32"
|
||||
|
||||
var/reg <- multiply var2 => "0f af/multiply *(ebp+" var2.stack-offset ") " reg "/r32"
|
||||
var/reg <- multiply var2/reg2 => "0f af/multiply %" reg2 " " reg "/r32"
|
||||
var/reg <- multiply *var2/reg2 => "0f af/multiply *" reg2 " " reg "/r32"
|
||||
|
||||
## Floating-point operations
|
||||
|
|
Loading…
Reference in New Issue