Fix negative check in show_add function

[s-celles]

Closes #864

[github-actions]

Benchmark Results (Julia vlts)

Time benchmarks

	master	3bddbd5...	master / 3bddbd5...
arithmetic/2-arg mul	13.1 ± 0.28 μs	12.8 ± 0.33 μs	1.02 ± 0.034
arithmetic/addition	0.0788 ± 0.00094 ms	0.0784 ± 0.0014 ms	1.01 ± 0.021
arithmetic/division	27 ± 0.63 μs	26.2 ± 0.6 μs	1.03 ± 0.034
arithmetic/multiplication	0.0629 ± 0.0019 ms	0.0612 ± 0.0026 ms	1.03 ± 0.053
overhead/acrule/a+2	2.4 ± 0.24 μs	2.37 ± 0.25 μs	1.02 ± 0.15
overhead/acrule/a+2+b	0.09 ± 0.01 μs	0.07 ± 0.01 μs	1.29 ± 0.23
overhead/acrule/a+b	4.14 ± 0.3 μs	4.09 ± 0.3 μs	1.01 ± 0.1
overhead/acrule/noop:Int	0.05 ± 0.001 μs	0.05 ± 0.01 μs	1 ± 0.2
overhead/acrule/noop:Sym	0.07 ± 0 μs	0.05 ± 0.01 μs	1.4 ± 0.28
overhead/get_degrees/large_poly	0.1 ± 0.001 μs	0.081 ± 0.01 μs	1.23 ± 0.15
overhead/rule/noop:Int	0.1 ± 0.01 μs	0.061 ± 0.01 μs	1.64 ± 0.31
overhead/rule/noop:Sym	0.08 ± 0.009 μs	0.06 ± 0.01 μs	1.33 ± 0.27
overhead/rule/noop:Term	0.08 ± 0.009 μs	0.07 ± 0.01 μs	1.14 ± 0.21
overhead/ruleset/noop:Int	30 ± 0 ns	30 ± 0 ns	1 ± 0
overhead/ruleset/noop:Sym	0.301 ± 0.001 μs	0.31 ± 0.01 μs	0.971 ± 0.031
overhead/ruleset/noop:Term	1.2 ± 0.021 μs	1.22 ± 0.02 μs	0.984 ± 0.024
overhead/simplify/noop:Int	30 ± 0 ns	30 ± 0 ns	1 ± 0
overhead/simplify/noop:Sym	30 ± 10 ns	30 ± 10 ns	1 ± 0.47
overhead/simplify/noop:Term	28.6 ± 1.3 μs	28.2 ± 0.9 μs	1.02 ± 0.058
overhead/simplify/randterm (+, *):serial	0.234 ± 0.0052 s	0.233 ± 0.0017 s	1 ± 0.024
overhead/simplify/randterm (+, *):thread	0.268 ± 0.02 s	0.263 ± 0.0084 s	1.02 ± 0.083
overhead/simplify/randterm (/, *):serial	0.0874 ± 0.0027 ms	0.0836 ± 0.0023 ms	1.05 ± 0.044
overhead/simplify/randterm (/, *):thread	0.0909 ± 0.0027 ms	0.0871 ± 0.0026 ms	1.04 ± 0.044
overhead/substitute/a	0.0421 ± 0.0012 ms	0.0418 ± 0.0012 ms	1.01 ± 0.041
overhead/substitute/a,b	0.0506 ± 0.0015 ms	0.0503 ± 0.0013 ms	1.01 ± 0.039
overhead/substitute/a,b,c	0.0462 ± 0.0012 ms	0.0455 ± 0.0013 ms	1.02 ± 0.04
polyform/easy_iszero	23.5 ± 0.49 μs	22.4 ± 0.48 μs	1.05 ± 0.032
polyform/isone	1.06 ± 0.033 ms	1.08 ± 0.037 ms	0.979 ± 0.046
polyform/isone:noop	0.09 ± 0.009 μs	0.09 ± 0.001 μs	1 ± 0.1
polyform/iszero	0.904 ± 0.026 ms	0.922 ± 0.033 ms	0.981 ± 0.045
polyform/iszero:noop	0.09 ± 0.01 μs	0.09 ± 0 μs	1 ± 0.11
polyform/simplify_fractions	1.16 ± 0.031 ms	1.17 ± 0.041 ms	0.986 ± 0.044
printing/large_poly	0.212 ± 0.0037 s	0.212 ± 0.0022 s	1 ± 0.02
time_to_load	1.27 ± 0.02 s	1.31 ± 0.0098 s	0.973 ± 0.017

Memory benchmarks

	master	3bddbd5...	master / 3bddbd5...
arithmetic/2-arg mul	0.078 k allocs: 2.72 kB	0.077 k allocs: 2.69 kB	1.01
arithmetic/addition	0.438 k allocs: 16 kB	0.438 k allocs: 16 kB	1
arithmetic/division	0.142 k allocs: 5.47 kB	0.141 k allocs: 5.44 kB	1.01
arithmetic/multiplication	0.356 k allocs: 11.7 kB	0.356 k allocs: 11.7 kB	1
overhead/acrule/a+2	0.034 k allocs: 1.25 kB	0.033 k allocs: 1.23 kB	1.01
overhead/acrule/a+2+b	0 allocs: 0 B	0 allocs: 0 B
overhead/acrule/a+b	0.047 k allocs: 1.8 kB	0.045 k allocs: 1.77 kB	1.02
overhead/acrule/noop:Int	0 allocs: 0 B	0 allocs: 0 B
overhead/acrule/noop:Sym	0 allocs: 0 B	0 allocs: 0 B
overhead/get_degrees/large_poly	2 allocs: 32 B	2 allocs: 32 B	1
overhead/rule/noop:Int	2 allocs: 0.0625 kB	2 allocs: 0.0625 kB	1
overhead/rule/noop:Sym	2 allocs: 0.0625 kB	2 allocs: 0.0625 kB	1
overhead/rule/noop:Term	2 allocs: 0.0625 kB	2 allocs: 0.0625 kB	1
overhead/ruleset/noop:Int	0 allocs: 0 B	0 allocs: 0 B
overhead/ruleset/noop:Sym	3 allocs: 0.109 kB	3 allocs: 0.109 kB	1
overhead/ruleset/noop:Term	12 allocs: 0.391 kB	12 allocs: 0.391 kB	1
overhead/simplify/noop:Int	0 allocs: 0 B	0 allocs: 0 B
overhead/simplify/noop:Sym	0 allocs: 0 B	0 allocs: 0 B
overhead/simplify/noop:Term	0.298 k allocs: 11.6 kB	0.282 k allocs: 11.4 kB	1.02
overhead/simplify/randterm (+, *):serial	2.3 M allocs: 0.0882 GB	2.21 M allocs: 0.0869 GB	1.02
overhead/simplify/randterm (+, *):thread	2.35 M allocs: 0.246 GB	2.26 M allocs: 0.245 GB	1.01
overhead/simplify/randterm (/, *):serial	0.844 k allocs: 30.4 kB	0.781 k allocs: 29.4 kB	1.03
overhead/simplify/randterm (/, *):thread	0.879 k allocs: 31.5 kB	0.816 k allocs: 30.5 kB	1.03
overhead/substitute/a	0.22 k allocs: 8.42 kB	0.22 k allocs: 8.42 kB	1
overhead/substitute/a,b	0.267 k allocs: 10.1 kB	0.267 k allocs: 10.1 kB	1
overhead/substitute/a,b,c	0.238 k allocs: 8.62 kB	0.238 k allocs: 8.62 kB	1
polyform/easy_iszero	0.133 k allocs: 4.58 kB	0.127 k allocs: 4.48 kB	1.02
polyform/isone	8.34 k allocs: 0.567 MB	8 k allocs: 0.561 MB	1.01
polyform/isone:noop	1 allocs: 16 B	1 allocs: 16 B	1
polyform/iszero	6.87 k allocs: 0.467 MB	6.72 k allocs: 0.465 MB	1.01
polyform/iszero:noop	1 allocs: 16 B	1 allocs: 16 B	1
polyform/simplify_fractions	8.82 k allocs: 0.59 MB	8.65 k allocs: 0.587 MB	1.01
printing/large_poly	1.86 M allocs: 0.082 GB	1.86 M allocs: 0.082 GB	1
time_to_load	0.153 k allocs: 14.5 kB	0.153 k allocs: 14.5 kB	1

[github-actions]

Benchmark Results (Julia v1)

Time benchmarks

	master	3bddbd5...	master / 3bddbd5...
arithmetic/2-arg mul	10.6 ± 0.27 μs	10.8 ± 0.35 μs	0.979 ± 0.04
arithmetic/addition	0.068 ± 0.00083 ms	0.0691 ± 0.00074 ms	0.984 ± 0.016
arithmetic/division	25 ± 0.63 μs	25.4 ± 0.69 μs	0.984 ± 0.036
arithmetic/multiplication	0.053 ± 0.0018 ms	0.0516 ± 0.0018 ms	1.03 ± 0.05
overhead/acrule/a+2	2.14 ± 0.07 μs	2.19 ± 0.05 μs	0.977 ± 0.039
overhead/acrule/a+2+b	0.08 ± 0.01 μs	0.08 ± 0.01 μs	1 ± 0.18
overhead/acrule/a+b	3.73 ± 0.11 μs	3.78 ± 0.07 μs	0.987 ± 0.034
overhead/acrule/noop:Int	30 ± 0 ns	30 ± 0 ns	1 ± 0
overhead/acrule/noop:Sym	0.07 ± 0.01 μs	0.061 ± 0.01 μs	1.15 ± 0.25
overhead/get_degrees/large_poly	0.09 ± 0.01 μs	0.09 ± 0.01 μs	1 ± 0.16
overhead/rule/noop:Int	0.07 ± 0.01 μs	0.061 ± 0.01 μs	1.15 ± 0.25
overhead/rule/noop:Sym	0.07 ± 0 μs	0.07 ± 0 μs	1 ± 0
overhead/rule/noop:Term	0.07 ± 0 μs	0.07 ± 0 μs	1 ± 0
overhead/ruleset/noop:Int	30 ± 0 ns	30 ± 0 ns	1 ± 0
overhead/ruleset/noop:Sym	0.32 ± 0.029 μs	0.321 ± 0.03 μs	0.997 ± 0.13
overhead/ruleset/noop:Term	1.18 ± 0.03 μs	1.18 ± 0.011 μs	0.999 ± 0.027
overhead/simplify/noop:Int	30 ± 0 ns	30 ± 0 ns	1 ± 0
overhead/simplify/noop:Sym	30 ± 10 ns	30 ± 10 ns	1 ± 0.47
overhead/simplify/noop:Term	26.6 ± 0.57 μs	26.7 ± 0.61 μs	0.997 ± 0.031
overhead/simplify/randterm (+, *):serial	0.191 ± 0.024 s	0.194 ± 0.027 s	0.984 ± 0.19
overhead/simplify/randterm (+, *):thread	0.253 ± 0.048 s	0.241 ± 0.043 s	1.05 ± 0.27
overhead/simplify/randterm (/, *):serial	0.0853 ± 0.0025 ms	0.0863 ± 0.0031 ms	0.988 ± 0.046
overhead/simplify/randterm (/, *):thread	0.0945 ± 0.0081 ms	0.0955 ± 0.0088 ms	0.99 ± 0.13
overhead/substitute/a	0.0339 ± 0.00071 ms	0.0347 ± 0.00079 ms	0.976 ± 0.03
overhead/substitute/a,b	0.0419 ± 0.00091 ms	0.0428 ± 0.001 ms	0.979 ± 0.032
overhead/substitute/a,b,c	0.0403 ± 0.00086 ms	0.0408 ± 0.0011 ms	0.988 ± 0.034
polyform/easy_iszero	19.1 ± 0.4 μs	19.3 ± 0.39 μs	0.986 ± 0.029
polyform/isone	0.914 ± 0.015 ms	0.918 ± 0.015 ms	0.995 ± 0.023
polyform/isone:noop	0.08 ± 0.001 μs	0.08 ± 0.01 μs	1 ± 0.13
polyform/iszero	0.792 ± 0.013 ms	0.798 ± 0.015 ms	0.993 ± 0.025
polyform/iszero:noop	0.09 ± 0.001 μs	0.08 ± 0.01 μs	1.12 ± 0.14
polyform/simplify_fractions	0.989 ± 0.049 ms	0.995 ± 0.017 ms	0.994 ± 0.052
printing/large_poly	0.191 ± 0.018 s	0.196 ± 0.012 s	0.972 ± 0.11
time_to_load	1.4 ± 0.012 s	1.41 ± 0.0088 s	0.995 ± 0.011

Memory benchmarks

	master	3bddbd5...	master / 3bddbd5...
arithmetic/2-arg mul	0.056 k allocs: 1.78 kB	0.056 k allocs: 1.78 kB	1
arithmetic/addition	0.3 k allocs: 10.3 kB	0.3 k allocs: 10.3 kB	1
arithmetic/division	0.132 k allocs: 4.77 kB	0.132 k allocs: 4.77 kB	1
arithmetic/multiplication	0.252 k allocs: 6.5 kB	0.252 k allocs: 6.5 kB	1
overhead/acrule/a+2	0.034 k allocs: 1.12 kB	0.034 k allocs: 1.12 kB	1
overhead/acrule/a+2+b	0 allocs: 0 B	0 allocs: 0 B
overhead/acrule/a+b	0.046 k allocs: 1.55 kB	0.046 k allocs: 1.55 kB	1
overhead/acrule/noop:Int	0 allocs: 0 B	0 allocs: 0 B
overhead/acrule/noop:Sym	0 allocs: 0 B	0 allocs: 0 B
overhead/get_degrees/large_poly	2 allocs: 32 B	2 allocs: 32 B	1
overhead/rule/noop:Int	2 allocs: 0.0625 kB	2 allocs: 0.0625 kB	1
overhead/rule/noop:Sym	2 allocs: 0.0625 kB	2 allocs: 0.0625 kB	1
overhead/rule/noop:Term	2 allocs: 0.0625 kB	2 allocs: 0.0625 kB	1
overhead/ruleset/noop:Int	0 allocs: 0 B	0 allocs: 0 B
overhead/ruleset/noop:Sym	3 allocs: 0.109 kB	3 allocs: 0.109 kB	1
overhead/ruleset/noop:Term	12 allocs: 0.391 kB	12 allocs: 0.391 kB	1
overhead/simplify/noop:Int	0 allocs: 0 B	0 allocs: 0 B
overhead/simplify/noop:Sym	0 allocs: 0 B	0 allocs: 0 B
overhead/simplify/noop:Term	0.284 k allocs: 10 kB	0.284 k allocs: 10 kB	1
overhead/simplify/randterm (+, *):serial	2.16 M allocs: 0.0755 GB	2.16 M allocs: 0.0754 GB	1
overhead/simplify/randterm (+, *):thread	2.32 M allocs: 0.237 GB	2.32 M allocs: 0.237 GB	1
overhead/simplify/randterm (/, *):serial	0.783 k allocs: 28.2 kB	0.783 k allocs: 28.2 kB	1
overhead/simplify/randterm (/, *):thread	0.918 k allocs: 0.0325 MB	0.918 k allocs: 0.0325 MB	1
overhead/substitute/a	0.172 k allocs: 6.05 kB	0.172 k allocs: 6.05 kB	1
overhead/substitute/a,b	0.223 k allocs: 7.69 kB	0.223 k allocs: 7.69 kB	1
overhead/substitute/a,b,c	0.229 k allocs: 7.81 kB	0.229 k allocs: 7.81 kB	1
polyform/easy_iszero	0.092 k allocs: 2.94 kB	0.092 k allocs: 2.94 kB	1
polyform/isone	10.9 k allocs: 0.579 MB	10.9 k allocs: 0.579 MB	1
polyform/isone:noop	1 allocs: 16 B	1 allocs: 16 B	1
polyform/iszero	8.97 k allocs: 0.48 MB	8.96 k allocs: 0.48 MB	1
polyform/iszero:noop	1 allocs: 16 B	1 allocs: 16 B	1
polyform/simplify_fractions	11.4 k allocs: 0.596 MB	11.4 k allocs: 0.596 MB	1
printing/large_poly	2.15 M allocs: 0.079 GB	2.15 M allocs: 0.079 GB	1
time_to_load	0.145 k allocs: 11 kB	0.145 k allocs: 11 kB	1

[s-celles]

Thanks @AayushSabharwal for this merge