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SRdeformations :: iszero

iszero -- Tests whether something is zero.

Synopsis

Description

Makes the test c == 0_class c. Why does zero not work for elements in the cokernel of a matrix?

i1 : A= matrix {{-1, -1, -1}, {1, 0, 0}, {0, 1, 0}, {0, 0, 1}}

o1 = | -1 -1 -1 |
     | 1  0  0  |
     | 0  1  0  |
     | 0  0  1  |

              4        3
o1 : Matrix ZZ  <--- ZZ
i2 : c1=cokerElement(vector {1,1,0,0},A)

o2 = | 2 |
     | 0 |
     | 0 |
     | 0 |

o2 : cokernel | -1 -1 -1 |
              | 1  0  0  |
              | 0  1  0  |
              | 0  0  1  |
i3 : c2=cokerElement(vector {1,-1,0,0},A)

o3 = 0

o3 : cokernel | -1 -1 -1 |
              | 1  0  0  |
              | 0  1  0  |
              | 0  0  1  |
i4 : c2==(0_(class c2))

o4 = true
i5 : iszero c2

o5 = true
i6 : iszero c1

o6 = false

See also

Ways to use iszero :